Nitrogen Fixing Agroforestry for Sustainable Upland Farming

SLOPING AGRICULTURAL LAND TECHNOLOGY(SALT): NITROGEN FIXING AGROFORESTRY FOR SUSTAINABLE SOIL AND WATER CONSERVATION Jeff Palmer Published By Mindanao Baptist Rural Life Center (MBRLC) Kinuskusan, Bansalan, Davao del Sur, Philippines With Funds Provided By Southern Mindanao Agricultural Programme (SMAP) SLOPING AGRICULTURAL LAND TECHNOLOGY (SALT): NITROGEN FIXING AGROFORESTRY FOR SUSTAINABLE SOIL AND WATER CONSERVATION Jeff Palmer Published By Mindanao Baptist Rural Life Center (MBRLC) Kinuskusan, Bansalan, Davao del Sur, Philippines With Funds Provided By Southern Mindanao Agricultural Programme (SMAP) Cover Photos: 1) An A-frame is used to find contour lines, the framework of any SALT project. 2) SALT, or Sloping Agricultural Land Technology, integrates fruit, field, vegetable crops within contour hedgerows of nitrogen-fixing species. and Published by the Mindanao Baptist Rural Life Center Kinuskusan, Bansalan Davao del Sur, Philippines. First Edition, 1996 Second Edition, 1999 With the purpose of facilitating information transfer, permission is hereby given for reproducing the contents of this manual, with the condition that proper acknowledgments are made and two copies are sent to the publisher. Bibliographic Citation: Palmer, J. Jeff. (1999). Sloping Agricultural Land Technology (SALT): Nitrogen Fixing Agroforestry for Sustainable Soil and Water Conservation, 2nd Edition.. A publication of the Mindanao Baptist Rural Life Center (MBRLC). ** pp. ACKNOWLEDGMENTS and PREFACE FOR SECOND EDITION Foremost, an acknowledgment of gratitude should be given to the Southern Mindanao Agricultural Programme (SMAP) for sponsoring the printing of this book. For many years, the Mindanao Baptist Rural Life Center (MBRLC) has been striving to find simple and applicable solutions to the problems that the upland farmers of southern Mindanao face day to day. Through the Testing and Development Division (T&D) of the MBRLC, other MBRLC staff members, and through farmers’ experiences, a tremendous amount of knowledge has been accumulated, especially in the area of hillside farming, namely the SALT technologies. SMAP, by supporting this publication, is helping to give a boost to the MBRLC’s capability of increasing the public’s general knowledge about the subject of nitrogenfixing agroforestry. Therefore, a great deal of gratitude goes to SMAP and its sponsorship. Namely, MBRLC would like to thank the Project Co-Directors of SMAP, Dashiel P. Indelible and Patrick Sweeting, for their support. Also, thanks to Jose Jorge C. (Boy) Yap, Jr. and Jeremy Cole, Co-Managers, SMAP, Zone 2. A belated thank you goes to Graham Garrod, former Project Co-Director and Ike Matulong, former Co-Manager, Zone 2. The staff of the MBRLC should also be given an acknowledgment for their hard work over the years in coming up with the ideas and data enclosed. The lessons presented are the results of many people’s work over the years that Sloping Agricultural Land Technology and its offshoots have been developed and used. This book would not be possible without the originators of the SALT, namely Harold R. Watson, MBRLC Director, Warlito A. Laquihon, Associate Director MBRLC, and Rodrigo “Rod” Calixtro, Farm Manager MBRLC. Finally, a special thanks to the Testing and Development staff of MBRLC who have compiled years and years of data and helped finalize this work: Gener Laquihon, Supervisor, Carlos Juano, Technician, and Paula Wilson, Journeyman/Editor. Jeff Palmer Director, MBRLC CONTENTS I) Introduction and Rationale II) What is NF Agroforestry? III) Background Information on How MBRLC Has Used Nitrogen-Fixing Agroforestry IV) Ideas and Lessons Learned About Nitrogen Fixing Agroforestry Lesson 1 Lesson 2 Lesson 3 Lesson 4 NFT/S hedgerows can adequately control erosion if planted and maintained properly. Not all legumes are NF plants and thus not all are beneficial to NF agroforestry systems. Management practices of NFT/S hedges affect biomass yields and thus crop production. The fertility of humid tropical farming systems greatly resides in the above- ground biomass (standing plants plus mulch) of the system. The mulching effect of the aboveground biomass does more to the physical properties of the soil than to the chemical properties. These improved physical properties lead to greater ability to utilize existing soil fertility, thus giving higher production. Total moisture is actually conserved in NF agroforestry systems as opposed to most traditional systems due to the mulching, shading, and cooling effect of the NF trees. Agroforesters have erroneously limited themselves to NF trees and overlooked the other nitrogen fixing plants in potential cropping schemes. Similarly, “cover crop” specialists have overlooked the trees and their benefits. The benefit of the NFP comes primarily from the dead and decaying biomass applied directly to the cropping zone. In NF agroforestry farming systems, phosphorous can quickly replace nitrogen as the limiting factor in sustainable production, especially in acidic soils. Page 1 4 10 13 13 18 22 27 Lesson 5 30 Lesson 6 32 Lesson 7 33 Lesson 8 Lesson 9 33 35 Lesson 10 The observation that NF alley cropping systems are more laborious than traditional farming systems is largely 38 a myth. A different type of labor is required, but possibly in lesser amounts. Lesson 11 Root invasion into cropping alleys of NF agroforestry systems such as SALT are not a serious problem, as much literature indicates. Crop production and consequently farm income can be greatly enhanced by NF agroforestry systems. One of the best hidden secrets about NF agroforestry species is their value as high quality animal feeds. Hedgerows for erosion control and N rich mulch are not necessarily harborers of unwanted pests and actually may help reduce certain pests by providing diversity in the system. 42 Lesson 12 Lesson 13 Lesson 14 43 44 46 V) Constraints to Nitrogen-Fixing Agroforestry VI) Conclusion VII) References/Further Reading VIII) Appendices 51 48 49 53 TABLES Table 1 Table 2 Table 3 Table 4 Table 5 Table 6 Available N, P, and K in selected crop residues. Cumulative soil losses in Test SALT (SALT vs. Non-SALT). Compilation of Runoff Test in Test SALT - 30 months. Most utilized and promising species of nitrogen fixing trees and shrubs for SALT hedgerows at MBRLC, 1988 to 1995. Corn yield response to differing vegetative barriers in SALT; Four croppings at MBRLC from 1994 to 1995. Hedgerow Biomass Test: The effects of cutting heights on Flemingia and rensonii, May 8, 1992 to Dec. 8, 1995. Sample taken from 2 meter linear double hedge of each species. Hedgerow Spacing Test - Eleven croppings, 1992 to 1996. Total kilograms of N, P, and K per hectare nutrient analysis in a SALT vs. a Non-SALT system. 7 15 16 20 22 24 Table 7 Table 8 26 28 Table 9 Table 10 Table 11 Table 12 Table 13 Table 14 Table 15 Table 16 Table 17 Yield of tomatoes (kg/plot) for four croppings with differing sources of fertility management. Physical properties comparison of a SALT and Non-SALT side by side plot. Moisture block readings - SALT vs. Non-SALT at an average depth of six inches, September 1991 to February 1994. Comparison of corn yields grown in SALT - Hedgerow cuttings added versus hedgerow cuttings removed. Twenty-three croppings from 1982 to 1993. Effects on corn production of live mulching versus “killed” mulch of close-growing cover crops Arachis pintoi and Desmodium heterophyllum. Comparison of labor inputs. SALT vs. Non-SALT, 1985 to 1990 measured in man days/hectare/year. Comparison of labor required by activity - New Test SALT, 20 months of recording. Hedgerow Spacing Test - Labor comparisons of hedgerow pruning and alley weeding on a per-hectare basis for one typical cropping of corn. A general comparison of production benefits of local farming practices and the NF SALT systems in the southern Philippines. Data gathered from tests and surveys. 30 31 32 34 35 39 40 41 44 FIGURES Figure 1 Figure 2 The law of inputs and outputs in regard to nutrient management and sustainability. Results of SALT fertility test in tons/ha. Treatment number corresponds to fertility treatment. 9 37 APPENDICES Appendix 1 Appendix 2 Appendix 3 Commonly Used NF Plants in the Southern Philippines. Nitrogen Fixing Species Tested and Used by MBRLC. MBRLC Rainfall Records, 1992 - 1995. 53 58 59 I) INTRODUCTION AND RATIONALE Introduction: At the start, let us lay down some parameters. This book is an account of one experience largely based upon the Sloping Agricultural Land Technology (SALT) projects in the southern Philippines. SALT was first developed by the Mindanao Baptist Rural Life Center (MBRLC), Kinuskusan, Bansalan, Davao del Sur in the mid 1970s. Since SALT's development, its idea, spirit, and focus on sustainable upland development has quickly spread throughout the Philippines as well as much of Asia. SALT was born in the foothills of Mt. Apo, the tallest mountain in the Philippines. Its birthplace was in a volcanic soil classified as a eutric nitisol. The soil is locally known as Miral clay loam and is characterized by a medium pH (5.0 to 5.5), medium to low levels of available nitrogen and phosphorous, and relatively high levels of potassium. The average annual rainfall of the area is about 2400 mm. (See Appendix 3, Rainfall records). The original one hectare demonstration plot of SALT was established and fully functional by 1978. It is located on a mountainside with an average slope of 30% in the demonstration area. The altitude is approximately 350 meters above sea level. Like other farming systems developed at MBRLC, SALT grew out of problems that farmers expressed to the MBRLC staff in formal meetings as well as during on-the-farm visitations (Watson and Laquihon, 1989). Low and declining farm yields were the foremost problems mentioned. Through closer examination, soil erosion was seen as the major contributor to this declining yield. Corn (Zea mays) production on hillside farms had dropped in 10 years from 3.5 to 0.5 tons per hectare per cropping. This book is an effort to of the first 25 years of SALT effort to look at agroforestry to view agroforestry through a Rationale: Agroforestry is the marriage of agriculture and forestry and is a relatively new term in the modern history of agriculture. Lundgren (1982) defines it as “a collective name for land-use systems in which woody perennials (trees, shrubs, etc.) are grown in association with herbaceous plants (crops, pastures) or livestock, in a spatial arrangement, a rotation or both; there are usually both ecological and economic interactions between the trees and other components of the system.” For those wanting a less academic definition, Young (1997) suggests that “Agroforest = growing trees on farms” if the term “growing” can mean managing and obtaining benefits and the word “farms” includes rangelands, forest land, etc. 1 look at the successes and failures and its offshoots. It is also an in a new way, challenging readers nitrogen fixing paradigm. Agroforestry, as used in this writing, is a holistic incorporation and inter-working of all things within the small family farm including animals, trees, crops, and natural resources. In reality, agroforestry is an old practice which from the beginning of time has been used by people to produce food and livelihood in order to provide for their families. It is a natural way of farming integrating many crops (trees and animals included), using a multi-storied approach and being diversified in terms of plants and animals on the small farm. This book treats the term “agroforestry” in this sense. Nitrogen fixing agroforestry is a challenge to observe farmers’ existing practices and to improve upon them through the use of nitrogen fixing plants. Traditionally, farmers’ practices have been judged to be inadequate and thus below standard when measured against “modern” agriculture, which relies heavily on improved varieties, commercial fertilizers, chemicals, etc. However, these so-called “modern” methods, even though scientifically proven, are often out of reach of the majority of the world’s farmers and can actually cause a decrease in productivity if not used properly. This book on nitrogen fixing agroforestry encourages the reader to acknowledge the existing farmers’ practices and use these as a starting point to help improve the situation of the local farmer. The difference is that the improvements to be introduced to the local farmers’ practices should be based on nitrogen fixing species. In preparing this material, an effort has been made to keep the message simple. In light of this simplicity, it was decided to make the book an easy reading one for a broad spectrum of readers. We wanted to provide a useful publication for the field technicians and people who do the work. Although non-academic in approach, this work is based upon some of the best information available today. "Implementors" of nitrogen fixing (NF) agroforestry systems may use and comment on our experience and the results given here. This work is also for the student wanting to get an overview of the topic. Lastly, SALT: Nitrogen Fixing Agroforestry for Sustainable Soil and Water Conservation is for the larger agencies which are considering implementing and funding projects with SALT-type agroforestry components. This work is not an “anti” book, either. This book, as well as our work over the years at the Mindanao Baptist Rural Life Center, is not anti-chemical, anti-non-nitrogen fixer, or “anti” to any structures or systems which promote conservation for the humid tropical uplands. It is "pro" nitrogen fixing hedgerows for erosion control and soil fertility enhancer. Most of all, this is a “pro” nitrogen fixing plant book. We will try to show the important role of the nitrogen 2 fixing plants (NFPs) in tropical agriculture based largely upon the experiences of the MBRLC. 3 II) WHAT IS NITROGEN FIXING AGROFORESTRY? The definition and “spirit” of NF agroforestry. Nitrogen fixing agroforestry, or “NF” agroforestry, is an approach to farming which acknowledges the benefits and encourages the incorporation of nitrogen fixing species into any and every farming system. The nitrogen fixing plant is seen not as an option to sustainable farming systems but rather as the foundation for the system. Nitrogen fixing agroforestry is open to all forms of nitrogen fixing plants found occurring naturally in the environment and seeks to use them symbiotically in farming systems to enhance the sustainability of the system. Nitrogen fixing agroforestry is not limited to trees which fix nitrogen or nitrogen fixing cover crops, but rather openly embraces all forms of nitrogen fixers as potential allies in creating sustainable farming systems. For example, if vegetative barriers are used to control soil erosion in a conservation cropping system, the pro-nitrogen-fixing agroforester immediately looks toward a nitrogen fixing plant to act as a barrier. Thus the term nitrogen fixing plant (designated NFP) will be used throughout this book. Although the systems discussed will rely heavily on nitrogen fixing trees, other plant forms such as shrubs and vines, perennials and annuals will be found within the total experience of NF agroforestry as well as free living NF organisms. Nitrogen fixing plants and their uniqueness. Nitrogen fixing plants are unique in the simple fact that they are nitrogen fixers. Even though all plants fix nitrogen to a certain degree, these plants unquestionably, when given the right conditions and organisms, can produce high levels of nitrogen which can be made available to agricultural systems. This fixation occurs through symbiotic relationships involving the NF plants and soil organisms such as Rhizobium and Frankia. One of the most limiting nutrients in agricultural production around the world is nitrogen, which is ironic since about 79% of the air we breathe is composed of gaseous nitrogen. The irony is that even though this is the most “in demand” nutrient by our agricultural systems and one of the most plentiful nutrients occurring naturally around us, nitrogen in its gaseous form is not available for use by the majority of our 4 agricultural crops. Industrialized nations rich in petroleum resources meet the demand for this nutrient by converting precious non-renewable fossil fuel resources into nitrogen-based fertilizers. Through a process of burning the fuels and creating a chemical reaction with atmospheric nitrogen, most of the world’s commercial nitrogen-based fertilizer is produced. This fertilizer is then sold on the market to rich and poor alike to enhance agricultural production in a variety of ways. However, the high cost of this process manifests itself both environmentally and economically. Can the environment and the small farmer afford the use of such chemicals? As beneficial as nitrogen-based commercial fertilizer is to the local farmer, some serious questions must be raised about the continuing practice of heavy reliance upon these products. Serious questions are now being raised about the sustainability of this process. For instance, as the depletion of the world’s reserves of fossil fuels occurs, what will happen to the price of the fuel and thus the commercial fertilizers which are produced from them? As competition for heating fuel, energy generation, transportation, and other items begins to grow, what will happen to the production of commercial fertilizers? Moreover, new questions are arising about the sustainability of using heavy applications of commercial fertilizers in agricultural systems. As heavier and heavier applications are being made to the soils, what are the long-term effects on the environment? Even more serious is the possibility that overfertilization with some commercially-produced nitrogen-based fertilizers may cause negative production in the long-term future due to sterilization of the soil, acidification, etc. This brings us to a simple law of inputs and outputs within most any system. Humorously stated,the axiom says: “In any system, if the outputs exceed the inputs, then the upkeep of that system becomes the downfall.” In other words, any system constantly generating “outputs” greater than its necessary production “inputs” is in danger of consuming its resource base for production and eventually destroying itself. This general rule, applicable to economics, transportation, etc., is applied here to sustainable farming systems. In any farming system, if the output of nutrients from the system exceeds the input of those nutrients, then we can say that system is non-sustainable. Eventually, due to constant outputs and inadequate inputs, yields will decline and the farmer will 5 abandon the system. Farming systems are made up of many types of outputs and inputs. Outputs include nutrient losses (soil erosion, leaching, volatilization, denitrification) as well as nutrient removal (crop harvest, animal feed, fuelwood harvest, burning). Soil erosion, in many cases, tends to be the major cause of nutrient loss, with up to two to three hundred tons per hectare per year on steep slopes in the humid tropics. Controlling soil erosion on sloping areas is a major step toward reducing the most serious wasteful output to any hillside farming system. However, controlling soil erosion usually is not enough to ensure that a balance exists between outputs and inputs in a particular system. Desirable outputs such as crop yield, animal feed, and fuelwood harvest can place a strain upon a balanced system. The more harvest, the more inputs are needed to replace the N, P, and K (as well as other nutrients) removed during that harvest. Inputs to agricultural systems include natural, inorganic and organic categories. Examples of natural inputs include existing nutrients in the soil profile, dust and other particles carried by the wind, rainfall which forces these particles down to earth, nitrogen fixed by lightning, and ecological nitrogen fixation caused by organisms naturally occurring in the soil. Inorganic inputs come mainly from commercially produced chemical fertilizers. Organic inputs come mostly from on-farm sources such as crop residues, animal manures, and green manures of NFPs. Although natural inputs of nitrogen vary from place to place, these methods can contribute from five to 15 kilograms of nitrogen to the system each year. The amount of N added through chemical fertilizers depends upon their cost and availability, as well as the ability of the local farmer to use them properly. The amount of N (and other nutrients) added by organic methods largely depends upon the management practices of the local farmer. For instance, crop residues added back to the soil can provide large amounts of N to the system. If those residues are burned, most of the available N returns to the atmosphere. The following table illustrates the amounts of the three major 6 nutrients available in selected crop residues on a per hectare basis. Table 1. Available N, P, and K in selected crop residues. Source: ATIK. <----------- Kg per hectare -------------> Residue Nitrogen Phosphorous Potassium Rice stover 30-50 4-7 150-250 Corn stover Peanut hay Cowpea hay 7-23 34-108 35-57 2-4 3-10 6-8 19-76 38-84 53-65 Unnecessary burning or removal of crop residues causes a tremendous output strain on any agricultural system. Not only that, removal by burning or feeding instead of decomposition, allows greater exposure of the soil surface by removing ground cover. This exposure can lead to greater potential for soil erosion and thus even greater nutrient loss in the system. Animal manures are another excellent input to a farming system. This resource is underutilized in many countries while others have known its benefits for centuries. Labor and cultural constraints have been the biggest barriers to the use of animal manures in certain areas of the world. Perhaps the most underutilized input (which is the focus of this book) for balancing farming systems nutrient input and output is the nitrogen fixing plant. Depending upon the usage, some NF agroforestry systems have been estimated to provide 40 to 60 tons of fresh organic matter (in the form of leafy biomass) to a farm system. Amounts of N as high as 200 kg/ha have been added. In areas where commercial fertilizers are not used due to high cost or unavailability, great potential exists for this type of input. 7 A graphical presentation of the balance of inputs and outputs in farming systems is presented below. 8 Figure 1. The law of inputs and outputs in regard to nutrient management and sustainability. 9 10 III) BACKGROUND INFORMATION ON HOW MBRLC HAS USED NITROGEN FIXING AGROFORESTRY One of the better advocates of nitrogen fixing agroforestry is the Mindanao Baptist Rural Life Center (MBRLC) and its 25 years of promoting the Sloping Agricultural Land Technologies (SALT). SALT definition and SALT models. As stated earlier, the original Sloping Agricultural Land Technology (SALT) was developed by the Mindanao Baptist Rural Life Center (MBRLC) in the mid-1970's. SALT was designed to aid hilly land farmers in making a decent living in a sustainable way on their fragile, sloping lands. Like other farming systems developed at the MBRLC, SALT grew out of problems that farmers expressed to the MBRLC staff in formal meetings as well as during on-farm visitations. SALT and its offshoots are packages of technology utilizing diversified crop production which integrate several soil and water conservation measures. Basically, SALT is a method of growing field crops, permanent crops, forages, and forestry species in contour bands 3 to 5 meters wide. Contoured rows of nitrogen fixing trees and/or shrubs (NFT/S) are thickly planted in double rows to form hedgerows. When a hedge is 1.5 to 2.0 m tall, it is cut back to a height of 50 to 100 cm and the cuttings are placed in the strips between the hedgerows, also called alleys, to serve as organic fertilizer and ground-cover mulch. The main thrust of all SALT technologies is to: 1) Minimize soil erosion, 2) improve and maintain soil fertility, and 3) provide food and income for the farm family. In short, the SALT idea has sought to provide sustainable balanced farming systems where the undesirable farm outputs (erosion, pollution, etc.) are minimized and desired outputs (production) are maximized. All of this is done in a NF framework where the inputs to the system are maintained largely by the use of NF plants. A brief description of each SALT is listed below. 11 SALT 1 Sloping Agricultural Land Technology. SALT 1 is a one- hectare agroforestry model established in 1978. SALT 1 is a system of growing food crops (45%) and permanent crops (30%) in 3 to 5 m contoured alleyways formed by double hedgerows of fast-growing NFT/S species (25%). SALT 1 uses minimal tillage and the formation of green terraces of the NFT/S to control erosion and act as a rich source of Nfertilizer through applying the leaf biomass to the soil. SALT 2 - Simple Agro-Livestock Technology. SALT 2 is a onehalf hectare agroforestry model established in 1987. It is basically a SALT 1 system which incorporates an animal component into the SALT farming scheme. The animal component in the original model is a 14-head goat dairy. One-fourth hectare of the 0.5 ha model is a standard SALT hedgerow/alley system devoted to food production for the family. The other 0.25 ha is a forage garden area producing food for the animal unit. Animal manures from the dairy are placed back into the system for fertilizer. 12 SALT 3 - Sustainable Agro-forest Land Technology. SALT 3, a twohectare agroforestry model established in 1987, is basically a farmer-focused, small-scale reforestation scheme. The lower hectare is devoted to a regular SALT 1 system and is called the food component. The upper hectare is devoted to a reforestation scheme which is simple and readily acceptable by the local farmer. The 1 ha forestry component is planted to tree species in “time zones.” These time zones are the harvest dates for different species, with progressively more valuable products reaching maturity at 1-5, 6-10, 11-15, and 16-20 years from establishment. SALT 4 - Small Agro-fruit Livelihood Technology. SALT 4, established in 1992, is a one-half hectare agroforestry model devoted to fruit production. The whole area is planted into SALT 1 type hedgerows. The alleyways on the lower one-fourth of the project are devoted to food production while the alleyways of the upper three-fourths are set aside for fruit production. The fruit alleyways are integrated with durian (SCIENTIFIC NAME), lanzones (SCIENTIFIC NAME), mangosteen (SCIENTIFIC NAME), kalamansi (SCIENTIFIC NAME), jackfruit (SCIENTIFIC NAME), rambutan (SCIENTIFIC NAME) and other highvalue fruit trees. Food crops are planted in the fruit alleys until the fruit trees reach maturity. 13 IV) IDEAS AND LESSONS LEARNED ABOUT NITROGEN FIXING AGROFORESTRY This section is the heart of this book. In the following pages the reader will find the lessons learned by the MBRLC as well as questions raised about NF agroforestry. Bear in mind as you read that this book was written to address primarily the technical, biophysical side of the topic. LESSON 1: NFT/S hedgerows can adequately control erosion if planted and maintained properly. For the last few years the question has been asked, “Can vegetative hedgerows adequately control soil erosion?” Thus the debate of those who are pro-structure and pro-grasses in vegetative barriers to control erosion on steep croplands versus those who rely heavily on vegetative barriers such as the NF tree/shrub. The answer of the MBRLC based upon the SALT experience and data is “yes,” NF trees and shrubs, if planted and maintained well, can adequately control erosion in most hillside farming situations. Erosion is caused by two primary forces: the raindrop splash, which loosens up the soil through kinetic energy upon impact, and moving water upon the soil surface. Two control measures are then needed to stop soil erosion. Number one is to stop the effect of the raindrop splash with a good ground cover. Tests around the world have confirmed this principle. Number two is to stop the surface water moving down a slope a barrier applied on the contour. Thus, the two approaches to erosion control: cover and barrier approach (Young, 1990). Most hillside conservation control systems have concentrated on controlling the surface flow of water using “barriers” within the system. Terraces, check dams, contouring, rock walls, etc., are good barrier approaches to erosion control and soil conservation. However, a barrier is only one part of a good soil conservation system. 14 Equally important is ground cover for soil and water conservation which prevents the raindrop splash from initiating erosion. If the ground is well covered--due to zero tillage, mulching, and/or good plant canopy--little erosion will occur. Therefore, in designing an erosion control system, attention must be paid to the cover as well as the barrier. The SALT technologies have focused on both of these aspects. The vegetative hedges of NFT/S are thickly seeded in double rows 50 cm apart along the contour. These double rows, which are spaced every 3 to 5 meters depending upon the slope and cropping system, become the barriers to fast-moving water as well as a source of mulching materials for soil cover through frequent prunings. Moreover, since these plants are NF in nature, the mulch provided is nitrogen-rich giving added fertility to the system. This results in improved crop production gives an extra soil conservation component to the system than just an inert barrier. How well can the thickly planted double hedges of NFT/S control erosion in the SALT system? In one test known as “Test SALT” conducted for six years at the MBRLC, erosion data was gathered from a side by side comparison of a traditional farmer’s cropping system (Non-SALT) and a SALT project. The individual plots were 0.08 ha in size and replicated for minimization of error. The slope of the plots averaged 18%. The Non-SALT treatments were cropped by no-till methods. Standing corn stalks were slashed three times and left on the soil surface. Corn was planted fairly close to the contour. The cropping system was a rotation that averaged two crops of corn (Zea mays) and one crop of mung beans (Vigna radiata) per year, in keeping with local cropping traditions. 15 The SALT plots were planted to NFT/S double contour hedgerows spaced about three to four meters apart. Every third cropping strip or “alley” was used for permanent crops: banana (Musa sp.), coffee (Coffea robusta and C. arabica), and calamondin (Citrus microcarpa). The annual or seasonal alleys were farmed using the same methods as the farmer treatment, except that the seasonal crops were planted along the contour to follow the hedges. Soil movement was measured by stakes placed within each treatment. Table 2. Cumulative soil losses in Test SALT (SALT vs. Non-SALT). Month from SALT Non-SALT Start (ton loss) (ton loss) 0 0 0 5 6.2 53.8 34 10.6 278.0 45 15.6 618.1 50 21.3 776.2 57 22.0 950.1 60 23.1 1025.4 68 21.4 1101.1 72 (Final) 20.2 1162.4 Tons/year 3.4 194.3 Table 2 shows that the SALT system wit thickly-planted NFT/S is effective in controlling soil erosion. Where the Non-SALT system yielded a total of almost 1,200 tons of erosion over the six years of the test, the SALT farm yielded only 20 tons. The annual rate of soil loss for SALT (3.4 T/ha/year) is much less than that of the Non-SALT system (194.3 T/ha/year). The data illustrate a soil loss reduction of approximately 98% from the Non-SALT to the SALT system. As 16 a check to the system, a separate runoff test was conducted on the same area described above. Water and soil runoff were collected in 2.5 cubic m sample tanks below one of the SALT and one of the Non-SALT plots. Measurements were taken over a two and one-half year period. The Non-SALT catchment basin (right) collected almost 113 times the soil of the SALT catchment and overflowed 15 times. From Table 3, the catchment basin below the Non-SALT treatment recorded more runoff in terms of water and sediment load. Out of 156 measurable rains during the recording period, 81 produced runoff in the Non-SALT treatment while only 9 produced runoff in the SALT treatment. The Non-SALT catchment had a total of 15 overflows (periods of intense rainfall causing spillover on the tanks) while the SALT catchment recorded only 6. Table 3. Compilation of Runoff Test in Test SALT - 30 months. Total rains with measurable precipitation Non-SALT 81 15 38,111 l 1,968 kg SALT 9 6 2,974 l 17 kg 156 RATIO 9:1 2.5:1 13:1 113:1 No. of collections No. basin overflows Water collected Soil collected The total water collected in the Non-SALT basin was 12.8 times as much (38,111 l) as that collected in the SALT basin (2,974 l). This indicates less surface runoff in the SALT system, meaning more water is being placed back into the soil, ensuring less erosion and greater water availability to crops. The total sediment load collected in the Non-SALT catchment was 115.7 times 17 higher (1,968 kg) than the SALT treatment (17 kg), showing NF agroforestry systems such as SALT 1 to be excellent erosion control systems. The combination of mulch and barrier used in SALT is the key to good erosion control in upland farming systems. Although grasses such as vetiver (Vetiveria zizanoides) and engineering structures may be better as barriers to soil erosion, the barrier is but one aspect of erosion control. We see that management of the cover can play as critical a role in controlling soil erosion as the barrier itself. The species of NFT/S used to control erosion at MBRLC have been selected over a number of years and are proven nitrogen fixers. Thus an added benefit from the cover provided by NFT/S barriers is a nitrogen-rich mulch. This nitrogen-rich mulch facilitates better crop growth, encouraging better production and sustainability as well as greater erosion control through healthier canopy cover. In a recent test established at the MBRLC, cement canals have been constructed below a new side by side SALT versus NonSALT test plot. The individual plots measure 12 by 33 meters and are located on a 12% slope. The treatments are triplicated giving a total of six plots (three SALT and three Non-SALT plots). The canals have been constructed to trap the total sediment load resulting from the erosion of each of the plots. Initial results from two months of data (starting with the 1996 rainy/cropping season) show a remarkably higher sedimentation below the Non-SALT plots as opposed to the SALT treatments. Total sediment load per Non-SALT canal is 384.8 kg during the time period listed above as opposed to 1.0 kg for the SALT treatment. This is a ratio of about 400:1, showing more erosion without the NF contour hedgerows than with. This test will be monitored for at least another three years to give even more accurate data on the total sediment load erosion from the test. However, it does support and confirm earlier MBRLC data that NFT/S hedgerows, when managed properly, can significantly reduce erosion in upland systems. LESSON 2 - Not all legumes are NF plants and therefore not all are beneficial to NF agroforestry systems. A major problem leading to erroneous results within alley cropping research has been the inclusion of non-nitrogen fixing plants as vegetative barriers. Two widely-accepted facts support this claim: 1) not all legumes are nitrogen fixing and 2) some non-legumes are nitrogen fixing. The word legume basically means “pod bearing plant,” and the most common examples are beans and pulses. Many plants in the legume family (Fabaceae or 18 Leguminosae) are nitrogen fixing; many however are not. Since verifying the nitrogen fixing ability of a plant involves a difficult technical process, the MBRLC has always used the rule of thumb that a plant which produces good NF nodules on the roots must be nitrogen fixing. To qualify as having “good NF nodules,” the plant must have many nodules which are moist and pinkish in color when crushed. Based upon this general rule, many well-known legumes have been excluded from the MBRLC’s line up of often-used nitrogen fixers. The genus Senna (formerly Cassia) has not been found to nodulate under conditions in the southern Philippines and therefore is not considered a potential hedgerow or component of our NF agroforesty systems. The nitrogen fixing ability of many of the plants in genus Acacia has also come into question. The MBRLC guidelines for a good species to be used in NF agroforestry systems as contour hedgerows are as follows: 1. 2. 3. 4. A nodulating, nitrogen fixing plant. Coppices readily under heavy pruning (12 times per year). Grows well in the MBRLC double hedgerow system. Produces at least 25 metric tons of fresh biomass/hectare/year based upon 5 m double hedgerow intervals for approximately 2000 linear meters per hectare. Readily sets seed for farmer reproducibility. Asexually/vegetatively reproduced. Tolerance to insects and diseases. 19 5. 6. 7. 8. 9. 10. 11. 12. 13. Able to grow well when thickly planted. Adaptable to a wide variety of soils and climates. Deep/tap rooted. Grows into a tree if left unattended. Usable for forage. Multi-purpose (i.e., fencing, fuel, feed, etc.). The most utilized and promising species for NF agroforestry systems at the MBRLC are listed below in Table 4 and ranked from highest to lowest in regard to fresh biomass yields. The biomass yield was determined on a per hectare basis for a five-meter spacing of hedgerows. The species of the genus Calliandra listed are excellent hedgerow candidates but have a problem with setting seed at lower altitudes. The MBRLC is at 350 meters and Calliandra sp., based upon local experience, needs at least 500 to 600 meters of altitude for good seed production. Ability to produce seed under local conditions is one criterion of a good hedgerow species. This characteristic is important for farmer reproducibility of the system. Leucaena diversifolia (small-leafed or acid-tolerant Leucaena) listed in the table shows promise as a contour hedgerow species but has not performed as well as others in actual farm trials. A good seed producer, this variety shows tolerance to the jumping plant lice (Heteropshylla cubana) which plagues larger leafed Leucaenas in this area. Where there is no jumping plant lice infestation, Leucaena leucocephala is one of the best NF contour hedgerows. Table 4. Most utilized and promising species of nitrogen fixing trees and shrubs for SALT hedgerows at MBRLC, 1988 to 1995. Fresh (T/ha) 51.9 49.8 42.3 36.5 34.3 34.1 31.0 28.5 Dry (T/ha) 16.1 15.9 11.8 8.4 5.8 9.5 6.5 9.1 NFT/S Species 1. Calliandra tetragona* 2. Calliandra calothyrsus 3. Leucaena diversifolia 4. Gliricidia sepium 5. Erythrina poeppigiana 6. Flemingia macrophylla 7. Desmodium rensonii 8. Indigofera anil** * First harvest - December 1990 ** First harvest - November 1989 All other species were planted and first harvested in 1988. 20 Gliricidia sepium is one of the most widely-used NFT/S in Asia. Well known for use as fencing material (largely via cuttings) and animal feed, Gliricidia is possibly one of the best species choice for hedgerows as well. Unfortunately, many people have not learned to plant Gliricidia by direct seeding instead of cuttings. Direct-seeded plantings have better tap root formation and less lateral root invasion into the alleyways of SALT systems. Moreover, direct seeding can reduce the amount of labor establishing a NF agroforestry system over the use of cuttings. The benefits of Gliricidia cuttings are evident. However, effort should be made to find local seed sources. Gliricidia seems only to set seed well in areas with dry zones having at least a 4 to 6 month dry period. Erythrinas are good nitrogen fixers and grow well from seeds or cuttings. However, due to their thorns, they are of limited use as hedgerows in NF agroforestry systems. Flemingia macrophylla may be the most widely adaptable NF contour hedgerow species for Asia since it also originates in this part of the world. It may also be the best NF hedge in terms of providing a long lasting ground cover after trimming. Many native and untested species of Flemingia grow around the area, and the possibility of finding and developing “undiscovered” cultivars exists. Desmodium rensonii is still fairly unknown around the world but is possibly the best animal feed in the tropics. With a crude protein content (23%) rivaling alfalfa in temperate climates, rensonii has been successfully tested as an animal feed for goats, sheep, cattle, rabbits, guinea pigs, swine, and fish. Indigofera tyesmani (anil) may be one of the more underexploited species. It shows promise in hedgerow systems, as an animal feed, and as a fuelwood crop. In simple tests at the MBRLC, Nubian goats have been fed a diet of 100% Indigofera for over a year, grown well and even kidded. It is showing to be one of the most promising new species being utilized by the MBRLC SALT systems and like Flemingia, it is also a native to the general region. In one interesting test conducted by the MBRLC to research the value of NF hedges, different vegetative barriers along the contour were tested for the effect on corn production grown in the corresponding alleyways. The hedges consisted of a double hedge of proven NFT/S (Desmodium rensonii + Indigofera anil), a double hedge of a NFT/S plus a grass (Desmodium rensonii + Vetiveria zizanoides), a grass double hedge (Vetiveria + Vetiveria), and a double hedge of a non-nitrogen fixing legume 21 (Senna spectabilis + Senna spectabilis). Each system was assumed to adequately control soil erosion, but in question was the effect of biomass applied from the specific hedge on crop growth in the alley. Senna spectabilis yielded the highest biomass produced of all four treatments with the Desmodium/Indigofera treatment being next. The Desmodium/Vetiveria treatment was third in total biomass production while the Vetiveria double hedge was last in terms of sheer biomass produced. Yields of four croppings of corn from the alleyways are listed in Table 5. Table 5. Corn yield response to differing vegetative barriers in SALT; Four croppings at MBRLC from 1994 to 1995. Dry shell weight(kg) 6.6 Double hedge type Nitrogen fixing trees (Desmodium/Indigofera) Nitrogen fixing tree + Grass strip (Desmodium/vetiver) Grass strips (Vetiveria zizanoides) Ton/ha 2.63 a 5.8 2.35 b 5.6 2.23 b, c Non-nitrogen fixing trees 5.0 2.12 c *Significant difference is determined using the one-tailed Z-test for alpha = 0.05 Using a one-tailed “Z” test, the effect of the vegetative barrier on corn production was demonstrated to be significantly greater in the NF hedge compared with any of the other hedgerow species combinations used in the trial. There was no significant difference between the effects of the NFT/grass hedge and those of the solid grass hedge on corn production. There was also no significant difference between the effects of the grass hedge and those of the non-NFT hedge. In spite of the fact that the non-NFT species S. spectabilis was found to be the largest biomass producer, in this trial it was shown to be a poor quality mulch for corn production. In both hedge combinations utilizing NFT species, the effect on corn production was significantly greater than that of S. spectabilis. This suggests that although biomass quantity is important, nitrogen fixing capabilities are equally if not of greater importance when considering hedgerow species. 22 Additional trials using other hedgerow species and crops are needed before general conclusions could be made. However, the data from this trial do sugges that careful selection of hedgerow species is an important factor for good crop production. And from tests and on-farm experience here at the MBRLC, it has been found to be important that these hedgerow species be nitrogen-fixing. It has been our observation that some research conducted in the past on alley cropping systems by other researchers might have reached different conclusions had good NF species been used for hedgerows in their trials. LESSON 3 - Management practices of NFT/S hedges affect biomass yields and thus crop production. From years of tests and field experience, the MBRLC has found that a crucial factor in successful NF agroforestry systems such as SALT is the proper management of the NFT/S used for the vegetative barrier. Trimming height, frequency of trimming, spacing of the hedgerows, maintaining hedgerow health, etc., all contribute to the successful, sustainable SALT system. Step number ten in the SALT manual is “Maintain your green terraces,” meaning the vegetative barrier of NFT/S. In expanding this idea, the MBRLC requirements for management of good “green terraces” are as follows: a. b. Use of nitrogen fixing (NF) species (such as those already mentioned). Thickly planted double hedgerows (not single and not triple rows). These double hedges should be spaced 50 centimeters apart along the contour. The spacing of individual NFT/S species within each of hedgerows is “as thick as possible.” The MBRLC general rule of thumb for in-row spacing is one plant every centimeter. Contour hedges spaced three to five meters apart (center of double hedge to center of double hedge) depending upon the steepness of the slope. Hedgerows maintained from 50 to 100 centimeters high. Trimming of hedges should not be lower than “knee high” because constant low trimming may cause dieback in a number of NF species used for vegetative barriers in SALT. Timely replanting of skips and missing hills within the hedgerow. Building of the terracing ability of the hedgerow by placing rocks, branches, etc., between the double rows. c. d. e. f. 23 In regard to the practice of trimming the hedges (item “d” above), tests and farmers’ experience have shown that trimming height and frequency of trimming the NF vegetative barriers affect the survivability and biomass production of the hedgerows. All of the major NFT/S species promoted by the MBRLC for use in hedgerow and forage systems are able to withstand heavy prunings of up to 12 times per year (once per month). However, in field situations where indiscriminate browsing may constantly occur from roaming animals, survivability under this heavy pruning and grazing may be reduced. Consequently, farmers who choose to trim their hedges “to the ground” for reduced shading effect may find their vegetative barriers dying back because of lack of sufficient reserve in the plant for coppicing. A test on the effects of hedgerow trimming height on biomass production was conducted at the MBRLC from 1992 to present. Double hedges of Flemingia macrophylla and Desmodium rensonii were planted and then given different treatments in terms of cutting height. Each species was trimmed at a 1.0 m “waist high” trim, 0.5 m “knee high” trim and ground height. The treatments were triplicated for each species and the results are as follows: 24 Table 6. Hedgerow Biomass Test: The effects of cutting heights on Flemingia and rensonii - May 8, 1992 to Dec. 8, 1995. Sample taken from 2 meter linear double hedge of each species. Flemingia (Kg) 1.39 1.26 0.47 Rensonii (Kg) 1.78 1.11 0.62 Average (Kg) 1.59a 1.19b 0.55c Treatment Waist high trim (1 m) Knee high trim (0.5 m) Ground trim *Significant difference is determined using the one tailed Z-test for alpha = 0.05 From the above data, the “waist high” trimming yields the best biomass production from the hedgerow with the “knee high” trimming second and the ground trimming a distant third. Thus the recommendation of good hedgerow maintenance is to trim somewhere between waist to knee high (100 to 50 cm). Any lower would cause significant yield reductions in biomass and consequently crop production. Higher trimming might cause excessive shading of the crops in the alleyways. In regard to hedgerow spacing (item “c” above), the MBRLC recommends alley spacing between hedgerows at 3 to 5 m depending upon slope. For seasonal cropping purposes, hedgerows should not be placed any closer together than 3 meters. Note: Crops requiring intensive cultivation should not be grown on extremely steep slopes (greater than 40%). At these slope extremes, MBRLC recommends permanent crop systems such as forages for animals (SALT 2), forestry species (SALT 3), and/or fruit trees (SALT 4). The spacing between hedges should be based drop. A standard rule of thumb is to allow no more vertical drop between hedges. Vertical drop can with a leveling instrument or more easily using method. upon vertical than one meter be determined the “eye-hand” In the eye-hand method, a person stands perpendicular to the slope along a contour line which has already been located. Facing uphill, he then holds his arms straight out in front of him, forming a ninety-degree angle between his arms and body. He then sights over the tips of his extended fingers into the ground before him. This sighting will be the point to begin the next contour hedgerow. Even though the eye-hand method may place contour hedges extremely far apart on flatter slopes, no hedgerows should be spaced over 5 m. Wider hedgerow spacing, although adequate for 25 erosion control, dilutes the fertilization effect of the hedgerow leaf matter because the trimmings must be evenly distributed over a larger area. In one test conducted at the MBRLC beginning in 1992, the effects of svaryied hedgerow spacing was monitored. Plots were replicated four times and each individual plot measured 10 by 20 meters. Five treatments of hedgerow spacing were tested: 6, 5, 4, 3 and 2 meter treatments per plot. Desmodium rensonii and Calliandra calothyrsus were used for the double hedge. Corn (Zea mais) was planted in the alleyways in such a way to give the same population per proportionate area. Thus, the two-meter treatment had one row of corn, while the three meter treatment had two rows of corn, and so on. The only crop planted was corn and an average of three crops per year were harvested. From the results in Table 7, the five-meter spacing yielded the highest per-hectare production. This may be an erroneous conclusion due to the fact that three of the four 5 m treatments were in favorable positions relative to the rest of the treatments. They were randomly placed in the lower plots which were more fertile. However, the actual yields show no added advantage (under local conditions) to spacing hedgerows 6 meters apart as opposed to 3 meters. In other words, any spacing of hedges greater than 3 meters did not give a significant yield increase (if one ignores the 5 meter aberration). This might indicate that closer hedgerow spacings could possibly yield as much as wider ones. This would increase soil holding capacity and fertility management resulting in increased sustainability of the system. Table 7. Hedgerow Spacing Test - Eleven croppings, 1992 to 1996. Treatment Spacing 2m 3m 4m 5m 6m Actual yield Tons/ha 2.69 a 3.23 b 3.22 b 3.66 c 3.17 b Productivity Tons/ha 5.41 4.85 4.31 4.57 3.81 *Significant difference is determined using the one tailed Z-test for alpha = 0.05 A good indicator of the fertility added back into the system from NF hedges is the productivity measurement above. Visibly, the individual corn plants and fruit in the 2 meter treatment 26 consistently produce better than those in the 3 meter treatment, which in turn are consistently better than in the 4 meter treatment, etc. This productivity measurement is based on observing the crops in the alleyways as compared on a per-unit basis not just a per-hectare basis. The numbers show that on a per-unit basis, the best “ear” of corn is produced in the 2 meter treatment. This is due to the high inputs of nitrogen-rich biomass from the closely spaced hedges. Therefore the closer the spacing, the higher the amount of biomass produced. Consequently, the greater the NF biomass availability (to a certain point) the greater the production of each individual plant. LESSON 4 - The fertility of farming systems in the humid tropics greatly resides in the above-ground biomass (standing plants plus ground cover mulch) of the system. When the tropical rain forests are removed due to logging and clearing, normally poor, nutrient-depleted, acid soils remain to be farmed. If one were to remove the ground cover biomass of most forested areas in the humid tropics and take a soil sample, the results would likely show a need for heavy additions of soil amendments to make the land farmable. However, the richest and most diverse ecosystems on the face of the earth are the tropical rain forests. Why then would the soil underneath the vegetative cover register so poorly by accepted measurable standards? One reason is that the fertility 27 of the tropical system resides largely in the biomass or “living matter” of the ecosystem. Moreover, most of that biomass is found aboveground and is not measurable using traditional techniques. When the soil of a tropical rain forest is tested in the laboratory, the aboveground portion where the storehouse of nutrients resides is not represented. High rainfall amounts, high humidty and high temperatures among other factors contribute to a rapid decomposition rate of biomass in the humid tropics. Moreover, these factors leading to high decomposition rates also contribute to poor soil fertility and rapid nutrient depletion in tropical farming systems. The secret to farming in these systems seems to be the promotion and maintenance of a high biomass input into the system serving as a nutrient pool for production. In a “total nutrient” test conducted at the MBRLC, an effort was made to look at the total profile in SALT and Non-SALT farming systems and see just where the storehouse of nutrients resided. As noted in the 1985 to 1990 Test SALT side by side comparison, when soil chemical properties were compared between the two systems, little to no difference was observed. However, the SALT system was yielding at a much higher rate than the NonSALT system, and the soil was soft with good drainage in SALT, while hard and compact in the Non-SALT system. Therefore, a test was set up in which the nutrients of the standing corn, the ground mulch, the soil, and the hedgerows (in SALT only) were measured and the data compiled to give a more complete picture of the nutrient balance between the two systems. The data are recorded as follows: Table 8. Total kilograms of N, P, and K per hectare nutrient analysis in a SALT vs. a Non-SALT system. <SALT NPK kg/ha> N P K 50.2 19.3 39.4 10.3 6.0 1.8 9.2 10.9 1.3 47.6 12.2 22.3 117.3 48.4 64.8 <Non-SALT NPK kg/ha> N P K 55.5 21.3 43.6 5.4 2.8 1.2 8.8 14.3 1.7 69.7 38.4 46.5 Particular Standing corn Ground mulch Soil Standing hedge TOTALS (kg/ha) The data show that the SALT and Non-SALT systems were virtually the same in total nutrients when the standing corn crops, ground mulch, and soil analysis nutrients were totaled. However, the superiority of the total nutrients in the SALT system becomes evident when the nutrients from the standing 28 hedges are added. This test was conducted after three years of cropping with corn as the major crop. The yields of the SALT system were greater than those of the Non-SALT (2.3 vs. 2.0 T/ha) which also testifies to greater system fertility. In a related test, the effects of different fertilizer sources in tomato production were monitored. This test was used to show the benefit of NF biomass as a fresh garden compost. NF biomass alone was tested against a mixture of animal manure and NF biomass, commercial fertilizer alone, and a control treatment of no added fertilization. The tomato fertilization treatments were: A. B. C. D. Control; no additional fertilizer (organic or inorganic) NF plant biomass in a “basket compost” NF plant biomass + animal manure in a “basket compost” Commercial fertilizer (5 gm 16-20-0 and 5 gm 46-0-0 per hill applied at planting) The results in Table 9 show that the lowest tomato yield was in the plots with no added fertilizer. There was a significant increase in yield with any amount and type or fertilizer. The commercial fertilizer plot gave the highest yield but was the most costly. The animal manure plus NF biomass was second. The NF biomass plot was third in terms of yield. The data show that biomass from NF plants can increase the yields of crops such as tomato. Since these plants are grown on the farm, adding available biomass is an economical way to provide fertility to crops. Moreover, manure additions to the NF plant biomass can take yields up another level. Even though the commercial fertilizer plots yielded the highest, the long-term effects to the system as well as the high cost of purchasing these inputs should be taken into consideration. The data show the role of biomass in tropical agriculture systems. The importance of utilizing NF biomass as an available and inexpensive fertilizer in such systems is also evident. Table 9. Yield of tomatoes (kg/plot) from 4 croppings utilizing different sources of fertilizers. Treatments B C kg/plot kg/plot 10.8 11.9 5.6 6.8 Harvest First Second A kg/plot 7.2 4.4 D kg/plot 14.0 7.9 Average 10.9 6.2 29 Third Fourth Mean (kg/plot) 10.5 12.5 8.6 12.5 17.5 11.6 15.0 18.8 13.1 15.5 21.3 14.6 13.3 17.5 LESSON 5 - The mulching effect of the aboveground biomass does more for the physical properties of the soil than for the chemical properties. These improved physical properties provide greater ability capacity to utilize existing soil fertility, thus giving higher production. Much emphasis has been put on the nutrients (primarily N) brought into the farming system by the use of NFPs. However, maintaining a good biomass mulch on the soil surface has another effect that may be just as important. Maintaining a good surface mulch in tropical agricultural systems improves the physical properties of the soil, enabling plants to better utilize soil nutrients. Though chemical differences in the soil between a SALT and Non-SALT system are hard to detect using standard measuring techniques, certain physical properties are readily seen. The important physical properties of the soil include water-holding capacity, drainage and aeration. These properties are largely the result of the decomposition of plant biomass on the soil surface. As the plant biomass decomposes on the soil surface, it provides for several physical functions of the top soil. These functions are essential for producing and maintaining healthy soil and healthy crops. 1) Humus. Humus is the brown to black upper layer of the soil consisting of partially or wholly decayed vegetable matter that provides nutrients for plants. It is organic matter decayed to a relatively stable, amorphous state. An important component of fertile soil, it affects physical properties such as soil structure, water retention, and erosion resistance. Humus is formed when soil microorganisms decompose animal and plant material into elements usable by plants. 2) Soil Organic Matter. 3) Soil Moisture Conservation. 4) Soil Organisms. 5) Surface mulch. These physical factors are important in maintaining a healthy soil and a healthy soil 30 making and is vial to producing healthy crops. This also illustrates differences between soil in a SALT and soil in a non-SALT agricultural system. By virute of applying plant biomass from the hedges to the soil as mulch, enhancement of these factors is facilitated and therefore the production of healthy crops. Roland Bunch (1997) says basically the same thing when he cites five principles his organization has learned about farming in the humid tropics: 1. 2. 3. 4. 5. Maximize organic matter production Keep the soil covered Use zero tillage Maintain biological diversity Feed plants through the mulch He summarizes all he has learned in stating, “In order for humid tropical agriculture to be both highly productive and sustainable, it must imitate the highly productive, millions-ofyears-old, humid tropical forest.” At the MBRLC in a seven-year-old plot of SALT versus NonSALT, fertility indicators were compared. Percent ground cover, earthworm castings per 30 cm square, infiltration rate, surface flow, and percolation were compared. The results are in Table 10. The percent ground cover was determined by randomly tossing a 30-cm square and estimating percent ground cover based upon visual references in standardized charts. Averages were taken for 10 tosses per each treatment. Earthworm castings were collected from 30 cm square areas using the same 30 cm square and random method. They were oven dried and weighed. Infiltration rate was based upon the rate of four liters of water entering the soil. A rectangular vegetable oil can (40 cm by 30 cm by 30 cm) with the bottom cut out was placed halfway into the soil and then water added. The can was place into the soil in a way to ensure minimal damage to the existing surface cover in each trial. The surface flow was determined by tipping a ten-gallon container on each treatment and measuring the resulting length of flow. The length of surface flow was measured from the point of the 10 gallons of water leaving the container to where the water finally was totally absorbed into the soil. Percolation was measured by digging a 15 cm cubed hole in 31 the ground and then filling it with one liter of water. The time needed for complete absorption of the water was recorded as the percolation time in each treatment. Table 10. Physical properties comparison of a SALT and Non-SALT side by side plot. Property Percent ground cover Earthworm castings Infiltration rate Surface flow Percolation SALT 92% 58 g 4'45" 1.7 m 15'55" Non-SALT 52% 4 g 12'25" 5.7 m 25'54" Ratio 2:1 14:1 1:3 1:3 1:2 *Data measured in 1992, MBRLC. In the areas tested, the SALT side gave continuously higher crop yields than the Non-SALT side. However, a test of major soil nutrients showed little or no difference between the two systems. The biomass analysis yields part of the explanation for this phenomenon. Another part was answered from the data which show that NF agroforestry systems do more to change the physical properties of the soil than the chemical properties. Since yields are so much better in the NF agroforestry treatment and since standard soil tests do not indicate this difference, it brings into question the method of testing for soil fertility applied in the tropics. Most standard soil tests are developed for temperate climates. Perhaps a new method of testing system fertility inclusive of the above-ground biomass could be designed for tropical agricultural systems. LESSON 6 - Total soil moisture is actually conserved in NF agroforestry systems as opposed to most traditional systems due to the mulching, shading, and cooling effects of the NF trees. In late August 1991, a soil moisture test was implemented in the Test SALT project. Gypsum blocks were buried at intervals in the Non-SALT farming system area and also in the SALT system area. Eleven initial blocks were buried a depth of 16 cm simulatubg the uptake of moisture by the crops from the “plow layer.” In May 1992, ten more blocks were added to the system to help monitor moisture levels more effectively. Using a <NAME of moisture meter company and type inserted here> moisture meter 32 which measures moisture in percent and bars, data was collected until February 1994. Results indicated that moisture patterns in both farming systems are amazingly similar. However, the overall soil moisture availability is higher in the SALT system than the Non-SALT system. This measurement is a value given by the moisture meter indicating the presence or lack of presence of water in the soil. A reading below 65 signifies the wilting point of most crops and indicates irrigation is needed. A comparison of the moisture use in a SALT system shows that the average moisture availability at a six-inch depth is the same in the permanent alleys and hedgerows and slightly less where seasonal crops are grown. Overall, each of the SALT components tends towards more available soil moisture than the Non-SALT farming system at a six-inch depth. Table 11. Moisture block readings - SALT vs. Non-SALT at an average depth of six-inches, September 1991 to February 1994. SALT SALT SALT Non-SALT SALT Corn Perm. Hedge Mean Mean Mean Mean Mean Reading 79 81 80 81 81 The data indicate that trees within a cropping system do not necessarily compete for moisture. Moreover, they may benefit one another in the long run. LESSON 7 - Agroforesters have often limited themselves to NF trees and overlooked other nitrogen fixing plants in potential cropping schemes. Similarly, cover crop specialists have often overlooked trees and their benefits. In the MBRLC SALT experience, we have attempted to pay attention to all types of NFPs. Not only are NF trees considered an integral part of nitrogen fixing agroforestry systems, but NF shrubs, crops, cover crops, and others are also incorporated. For instance, in SALT 1, a heavy reliance is made upon the NF hedgerow. However, use of NF crops is encouraged in rotation with non-NF crops (Step 9 in the SALT methodology). Moreover, good NF cover crops are incorporated into the permanent crop alleys to provide additional soil erosion control and fertility management. 33 Due to specialization in agricultural/agroforestry fields, the tendency is often to overlook plants which do not fit in with a particular discipline. For instance, a forester might be interested in Leucaena, Gliricidia, or Calliandra, but disregard shrubs such as Desmodium and Flemingia. Since these species are “shrubs” and not “trees,” they are not considered by many forestry people. Conversely, cover crop specialists are interested in plants such as Arachis, Mimosa, and Mucuna, and ignore erect NF species. A successful agroforester needs to look at how the whole scheme of NF plants available and what plants best fit into local farmers’ practices. From crop rotation with nitrogen fixing and non-nitrogen fixing crops, to hedgerows of NFPs and reforestation with NF trees, each system is in need of the NF potential. LESSON 8 - Benefits of the NFP comes primarily from the dead and decaying biomass applied directly to the cropping zone. Much debate has arisen over the actual source of NFP benefits. Do they come from the roots where the NF nodules occur? Are they gained from a “leaching” of N around the plant itself into the cropping areas? The MBRLC data show that the primary benefits of NFPs come from the dead and decaying biomass “harvested” from the NF plant and applied to the crop as mulch. Growing a NF plant by itself does not insure soil enrichment. A nitrogen fixing plant does fix nitrogen but is rather “selfish.” In other words, the NFP makes only enough nitrogen for its own use and not for others. However, depending upon management practices, the NFP can be coerced to “give” other plants the nitrogen it produces. This is demonstrated from the results of a test called “Nitrogen Test” conducted at the MBRLC. The test consisted of 23 croppings of corn covering a period from 1982 to 1993. The test location was an established SALT project on a 30% slope, and an average of two crops of corn per year were grown. One plot received all of the hedgerow prunings of Leucaena and Flemingia while the other plot received none of the hedgerow prunings; those were removed and added to another plot. Both treatments were grown within the framework of an NF agroforestry system, but the cuttings of the NF species were applied only to the crops in one treatment. The results are as follows: Table 12. Comparison of corn yields grown in SALT - Hedgerow cuttings added versus hedgerow cuttings removed. Twenty-three croppings from 1982 to 1993. 34 Plot A Hedges Removed Average Ann. Yield (T/ha) *Z test at alpha = 0.05 0.87 a Plot B Hedges Added 2.02 b The data show that corn growing in close proximity to NF hedgerows does not necessarily reap the NF benefits of those hedges through leaching or contact with the nodules. On the contrary, an adjoining plot where the NF hedge trimmings are added as a nitrogen-rich mulch shows excellent yield response to the biomass. An almost threefold increase in yield is recognized by the addition of the NF mulch as opposed to dependence on root nodulation only. This fact is very important for those who promote the use of the NF vegetative barriers as animal feed. Even though these species do make good animal feed, a separate area devoted exclusively to forage production should be maintained and its fertility replenished through the spreading of animal manures in the forage area. This principle has also been tested using NF cover crops in corn production systems. In systems using Desmodium heterophyllum and Arachis pintoi, treatments where the live mulch has been killed back to cause the biomass to “drop” its nitrogen are the highest yielding. In each case where a live is used for corn production, significant yield reduction is observed. Table 13. Effects on corn production using live mulching versus “killed” mulch of close-growing cover crops Arachis pintoi and Desmodium heterophyllum. <--- Corn yield in tons/ha ---> Killed mulch Live mulch 3.1 0.9 2.6 0.6 Treatment D. heterophyllum A. pintoi LESSON 9 - In NF agroforestry farming systems, phosphorous can quickly replace 35 nitrogen as the limiting factor in sustainable production, especially in acidic soils. One negative observation about NF agroforestry systems in the experience of the MBRLC is in relation to the nutrient phosphorous. Medium amounts of phosphorous are needed by most crops to ensure good growth and fruiting. In the soil, phosphorous is highly bound to soil particles and can become “fixed,” or not available to cropping systems. In acid soils this fixation becomes even more severe to the point that phosphorous sometimes becomes the major limiting factor. Phosphorous is not a highly mobile nutrient due to the high fixation rate to soil particles. Efforts to add mineral phosphates to the soil are wasted unless they are added fairly close to plant rooting zones for ready uptake. Also, phosphorous is naturally available in the soil only through weathering of existing minerals. In intensive croppings of corn in SALT systems, phosphorous deficiencies have appeared. These systems involved two to three crops of corn per year. Corn is a heavy user of phosphorous, so most soils would show phosphorous depletion under this kind of cropping scheme. One test in particular, called “Fertility Test,” was designed to monitor the problem of depleting phosphorous reserves. Three replications of twelve different fertilizer treatments were applied. The test was run for seven croppings of corn, and the alleys chosen for the test had been planted to corn fairly consistently for ten years. The fertilizer application per treatment, measured in kg/ha applied per plot, was as follows: N T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 0 90 45 90 45 0 0 0 0 45 0 45 P 0 60 30 0 0 60 30 0 0 30 30 0 K 0 0 30 0 0 0 0 60 30 0 30 30 In the graph below, the best corn production response was 36 from the applications which had at least a combination of nitrogen and phosphorous (Treatments 2, 3 and 10). However, the nitrogen additions alone were found to be no better than phosphorous additions (Treatments 4/5 vs. 6/7). This may indicate that under low-input systems such as SALT type NF agroforestry systems, additional inputs of commercially produced fertilizers might be more wisely focused on phosphorous applications instead of nitrogen. The biomass from the hedgerow supplies the system with a good deal of nitrogen. Since these systems are moderate producers, the addition of small amounts of nitrogen in the form of commercial fertilizers may not give good returns economically. Less expensive phosphate fertilizers coupled with nitrogen-rich biomass may give the better economic yield. A final observation concerns the insignificant response to added potassium (Treatments 8 and 9). This is attributed to the fact that soils in the MBRLC area are already moderately high in potassium without any additional inputs. Results of SALT Fertility Test 6 5 Yield (Tons/ha) 4 3 2 1 0 t1 t3 t5 t7 t9 Treatment Number t11 37 LESSON 10 - The traditional view that NF alley cropping systems are more laborious than traditional farming systems is largely a myth. A different type of labor is required, but possibly in lesser amounts. One of the perceived constraints by many to using NF alley cropping systems such as SALT is the belief that these systems tend to be more laborious than traditional farming systems. However, according to the experiences of the MBRLC and the SALT technologies, the opposite might be true. In the Test-SALT research conducted from 1985 to 1990, labor requirements between the two systems were monitored and recorded. This test was a side by side comparison of the SALT farming system (utilizing NF contour hedgerows) and a traditional (to the local area) Non-SALT farming system. Although both SALT (left) and Non-SALT (right) strips require weeding, the Non-SALT area is greater, and weeds are not suppressed by mulch from the hedgerows. Therefore, the Non-SALT area requires more weeding labor. Until this test, the MBRLC staff thought that SALT farming would be more laborious. The hedgerows were perceived to be the extra labor factor due to the need for locating, planting, and maintaining (which includes pruning). However, Table 14 shows that although more labor was involved in the first year of the project, less labor was involved in the succeeding four years. The relatively low labor requirements in SALT from 1986 to 1989 can be explained by the smaller area under annual crops and the low labor intensity in land under perennial crops. Also, even though hedgerow pruning labor is involved in the SALT system, the benefit of labor saving in mulching and weed control more than offsets the “extra” hedgerow labor. 38 Table 14. Comparison of labor inputs. SALT vs. Non-SALT, 1985 to 1990 measured in man days/hectare/year. SALT Labor MD/Ha/Yr 354 237 152 172 270 316 250 Non-SALT Labor MD/Ha/Yr 337 290 206 211 290 208 257 Difference (SALT-Non-SALT) +17 (-5%) -53 (18%) -54 (26%) -39 (19%) -20 (7%) +108 (-52%) Total = -41 MD/ha/yr Average = 2.7% lower Year 1985 1986 1987 1988 1989 1990 Average In 1990 the labor requirement in SALT became higher than in Non-SALT due to the high production of permanent crops (primarily citrus and coffee). Thus labor in SALT tends to increase with time until the permanent crops attain maturity and reach maximum production. The increase in labor in the SALT treatment is primarily harvest labor of permanent crops. In both treatments, the largest percentage of labor was from weeding of annual crops, primarily corn. On the average, annual labor input for SALT was slightly lower than that of the farm treatment for the six-year period. In a separate study of a new area planted to a similar side by side test, labor was measured and recorded as labor type per system. This area, called New Test SALT, is currently being monitored. The results from the first year and one-half of labor comparison between a SALT and Non-SALT system are found in Table 15. The data are expressed in actual hours worked per 10 x 35 meter plot. Three plots of the SALT system and three plots of the Non-SALT system are alternately located side by side on a slope of about 16%. Each plot is exactly like the others in terms of seasonal and permanent crops with the exception of a double contour hedgerow of NF species located every three to four meters apart in the SALT treatments. Table 15. Comparison of labor required by activity - New Test SALT, 20 months of recording. <----- Average per plot -----> SALT Non-SALT Hours spent Hours spent Activity Land preparation 191.3 191.3 Establishing contours 10.0 39 Hedgerow pruning Land prep./seasonal crops Planting seasonal crops Weeding seasonal crops Harvesting seasonal crops Planting of permanent crops Weeding of permanent crops Totals 18.0 5.1 14.0 75.5 21.0 6.0 1.7 342.6 4.8 18.4 122.8 30.8 6.1 374.2 The data show for the first 20 months of the test, less labor was required in the SALT system than in the Non-SALT system. SALT requires “extra” hedgerow labor, but the overall labor is less because of decreased cropping area to weed and decreased weed growth due to mulching. Even though the SALT treatment has less area for seasonal crop (corn) production, it has consistently outyielded the Non-SALT treatment on a perhectare basis (2.3 tons/ha versus 2.1 tons/ha over five croppings). This supports the idea that hedgerows, when used properly, can help reduce labor requirements instead of increasing them. Much is written about labor intensity establishing and pruning the hedges. However, the above data show that this “extra” labor is compensated for by a reduced need for weeding. Data from a separate test further prove this point. In this test, actual labor required to trim hedges was compared to that needed to weed the cropping area of corn mulched by the prunings. 40 This test was conducted in the hedgerow spacing test (described earlier) with a varying hedgerow spacing of two, three, four, five, and six meters (Table 16). Table 16. Hedgerow Spacing Test - Labor comparisons of hedgerow pruning and alley weeding on a per-hectare basis for one typical cropping of corn. Hedge Labor (MD) 14.1 10.9 7.7 6.7 5.6 Weeding Labor (MD) 11.0 20.4 25.0 29.0 32.2 Total Labor (MD) 25.1 31.3 32.7 35.7 37.8 Treatment Spacing 2m 3m 4m 5m 6m *Hedge labor is cased upon four actual measured trimmings. **Weeding labor is measured for every weeding in the test, which averages two times per cropping. The above data confirm that in a hedgerow/alley cropping system such as SALT, the hedges when properly used for mulching, can actually reduce labor requirements in a system. From the table, the more hedges to prune (2 m treatment), the less weeding required. Therefore, with more hedges, there is less overall labor when only comparing these two labor components in the system. Conversely, with wider or fewer hedges (6 m spacings) less hedge labor is required but total labor per hectare is greater. However, wide hedgerow spacings do not supply sufficient mulch to control weed growth. In short, the hedgerow can lead to less overall labor in the SALT system as opposed to a Non-SALT system. This labor reduction is mainly brought about by the mulching factor of the NF vegetative barriers. Pruning is a different type of labor, considered an “easier” labor than weeding of seasonal crops. LESSON 11 - Root invasion into cropping alleys of NF agroforestry systems such as SALT is not as much a serious problem as some literature may indicate. The literature on NF hedgerow cropping systems such as the SALT system often comments on potential competition from hedgerow roots invading the alleyways where the crops grow. Some even go so far as to recommend “root pruning” to reduce NFT/S and crop competition for nutrients and moisture. Results at the MBRLC have shown that root competition in 41 SALT systems is minimal. Root studies have shown that under normal conditions, the roots of the hedges do invade the alleyways and even meet in the middle of those alleys. Further studies showed that about 75% of the root biomass of the hedgerow was found within the top 15 centimeters of the soil, generally considered the rooting zone for crops. However, none of the major species produced large roots which interfered with cropping practices. Perhaps one reason for this is the frequent prunings conducted in SALT. Hedge pruning is recommended when the hedge reaches a height of about one meter from the initial pruning. In the MBRLC context, this allows for an average of eight prunings and thus eight applications of nitrogen rich biomass to the system per year. This heavy schedule of pruning keeps the basal stems of the NFPs from getting large and also reduces the risk of shading out alley crops. Moreover, this frequent top pruning also prevents the formation of large lateral roots. As the branches are lopped, a percentage of the roots die back due to shock in the plant. The majority of the roots that die back are the ones farthest from the main plant, which are the ones in the alleyway. This dieback of roots in the alleyway also gives an extra burst of nitrogen release, as many of the nodules for the NFP are on these “feeder” roots. Furthermore, if roots which enter the cropping alleyways provide competition, the tests have shown more improved crop yields with hedges than without. And if competition from ivading roots exists, higher yields due to the presence of hedgerows more than offset losses from competition. LESSON 12 - Crop production and consequently farm income are enhanced by NF agroforestry systems. SALT systems which make use of NF fixing hedges and plants have consistently shown higher and more sustainable production, especially when compared to local farming practices. The nitrogen fixing capacity of the system yields itself to good crop production and increased farm income. This combination makes NF agroforestry systems attractive as viable farming systems in the humid tropics. In the area surrounding the MBRLC, average annual corn yields range from 500 to 1,000 kg/ha under local systems and conditions. Introduction of NF hedges have enabled farmers to increase this yield to at least 2,000 kg/ha within the first two to three years of implementation. Moreover, in a SALT 2 system 42 with the additional use of animal manures, corn yields have reached 4,000 kg/ha. In terms of income, each of the SALT agroforestry systems achieves good results. Below is a general summary of the comparisons of the SALT systems and their benefits. Table 17. A general comparison of production benefits of local farming practices and the NF SALT systems in the southern Philippines. Data gathered from tests and surveys. Farming System Traditional systems SALT 1 (NF hedgerow system) SALT 2 (Animal system + NF species/hedges) SALT 3 (Small scale reforestation scheme with NF species) SALT 4 (Fruit production with NF hedges) Average Corn yield T/ha 0.5-1.0 2.0-2.5 Average Annual Income P/ha 6,000 14,400 3.0-4.0 32,000 2.0-2.5 20,000 LESSON 13 - One of the best-hidden secrets about NF agroforestry species is their value as quality animal feeds. Despite the data and available literature, the full value of NF species is still largely overlooked. Many farmers and technicians verbally acknowledge the value of NFPs as forages when asked or prodded, but relatively little thought is given to them when forage systems are implemented for domesticated animals. 43 Many NF species are excellent animal feeds. Desmodium rensonii has been called “the alfalfa of the tropics” because of the 23% crude protein content in the leaf matter. D. rensonii readily seeds and can be fed directly to most ruminants and non-ruminants. Years of feeding pure rensonii to goats at the MBRLC testify to its excellent forage potential. Rensonii can be fed solely to rabbits with little side effects and is good for cattle, fish, swine, sheep, and guinea pig. Some bloating has been observed in sheep fed purely rensonii, but that problem is contained by mixing in a little grass. Gliricidia sepium may be the most overlooked forage that grows readily throughout Asia. Some literature claims that wilting is necessary before feeding to livestock. However, fresh cuttings are usually taken out of your hand when entering the MBRLC goat barns. Gliricidia is noted to be a good feed for cattle, goats, and sheep. No ill effects on goats have been noticed, but some bloating has been observed in sheep if fed exclusively Gliricidia for long periods of time. Ipil-ipil or Leucaena leucocephala has recently been discarded as a forage and multi-purpose NFP due to the jumping plant lice invasion. Overall, Leucaena may be one of the best NFP sources of feed, whether fed fresh used as leaf meal. Experience has shown that after livestock become accustomed to eating Leucaena, heavy feedings of the plant can be given. In terms of milk production in goats, Leucaena is one of the best species to give (Laquihon, et. al., 1996). Flemingia macrophylla has also been used extensively by the MBRLC as an animal feed. Although not as palatable and digestible as some of the species mentioned earlier, Flemingia is used as a “filler” feed. However, goats fed exclusively with Flemingia are noted for poor growth. Indigofera tyesmani (anil), a fairly new species at the MBRLC, has been tested initially for goat feed. Initial results have shown great promise for this plant as an animal forage. In one simple test, a small herd of crossbred goats (Nubian x native) were raised a whole year on nothing but water and Indigofera. Two of the does in the test were bred and kidded during the test with no adverse affects to the pregnancy and parturition. 44 The Calliandras are also excellent forages. These species are reported high in tannin, which can cause problems in animals such as hair loss, poor weight gain and poor performance. Little effects of this nature have been observed at MBRLC feeding Calliandras. One observation should be made about how the NFPs have been used in the MBRLC animal systems. Primarily, they have been used in cut-and-carry systems, not free grazing. Most SALT 2 type systems at the MBRLC are with penned animals, and the forage is cut twice daily and brought to them. This controls what and how much the animal unit consumes. If these species are grazed heavily, they possibly would not survive. More about this topic is covered in Appendix 1 which relates the MBRLC experience with currently used NF forages. LESSON 14 - Hedgerows for erosion control and mulch production are not necessarily havens for unwanted pests and may actually help reduce certain pests by providing diversity in the system. Much ado has been made in literature about the problem of contour hedgerow farming systems such as SALT harboring unwanted pests. Many have cited the “possible” infestation of cropping areas by pests being harbored in the vegetative barrier. While a possibility, this has not been observed at the MBRLC. One major pest in SALT over the years has been field mice and/or rats. They live in the hedgerows and other parts of the farm and damage newly planted crops. However, most Non-SALT farmers in the area have the same problem even without contoured vegetative barriers, as in the SALT system. In terms of pest management, very few if any commercial pesticides are used in SALT. This is due to the fact that 1) they are costly to the farmer and 2) spraying of insecticides also kills beneficial insects. Therefore, a balance is sought in which some crop damage due to disease and pests is allowed and natural predators are encouraged to help control the problem. In extreme cases of infestation, timely applications of appropriate chemicals in appropriate amounts can be made. However, most SALT tests and projects of the MBRLC are not sprayed unless absolutely necessary. While true that the NF hedges may harbor fungi, bacteria, insects, and rodents, which may be detrimental to the crops in the alleys, these same barriers offer diversity which may help reduce other pest problems. For example, hedges can act as barriers to pest migration so that instead of destroying a whole 45 field, the “stripping” effect breaks up the crop, localizing and minimizing pest problems. Moreover, while serving as a potential host to unwanted organisms, hedges also serve as a host to beneficial ones. Further research and documentation is needed in this area. V) CONSTRAINTS TO NITROGEN FIXING AGROFORESTRY Up to this point, mostly positive lessons have been pointed out about NF agroforestry systems. However, some questions may be raised along with some unexplored ideas. Since this book has approached the topic from mainly a biophysical perspective, the following constraints will also be discussed in this manner. Although we acknowledge other restraints, such as the socioeconomic, they will not be considered here. First of all, a great need remains for further testing of these systems in other climates, ecosystems, etc. The data and lessons learned within this book are limited largely to the experiences of the Mindanao Baptist Rural Life Center. Even though the staff of MBRLC has traveled extensively in tropical Asia and seen most of these same results, the NF agroforestry case would be made stronger if more research and experience from other organizations and areas were shared. Experience from dry zones, high altitude zones, etc., would be very valuable. Second is the problem of acid soils and non-nodulation of proven nitrogen fixing species. The more acidic the soil, the lower the chance of nodulation. Even though the pH of the soil around the MBRLC is mildly acidic (5.0 to 5.5), it is still within the range of nodulation ability for most species. Other in Asia have claimed to have problems with SALT due to the acidic soils of their particular area. This may be a true observation. Since this is a strong possibility for limiting NF agroforestry systems, more research is needed in getting NF species to nodulate in these types of soils as well as continued searching for local NF species that nodulate well under such conditions. A third problem is the apparent lack of benefit of the nitrogen rich mulch on NF crops within the alleyways of SALT type systems. Most MBRLC tests are carried out on corn since this is the food staple crop in the area of the Center. However, we have observed that short growing crops such as vegetables and NF crops such as beans do not seem to benefit from the system as readily as corn. This may be due to shading effects on the lower growing crops and the apparent fact that NF crops such as beans do not benefit from the extra nitrogen given by the NF mulch. Further tests and research need to be conducted in these areas also. 46 VI) CONCLUSION In conclusion, this book has been about promoting nitrogen fixing agroforestry farming systems based largely upon two decades of experience at the Mindanao Baptist Rural Life Center. However, the MBRLC also promotes and widely uses non-nitrogen fixing species and crops and integrates them fully into all of the SALT farming systems. Thus the MBRLC is not limited to exclusively using NFPs for reforestation, forage systems, erosion control, etc. Many trees and plants which are nonnitrogen fixing are wonderfully effective for these uses. However, NFPs have always been the base for building of sustainable systems, and that is the encouragement of this book. Conservation and sustainability in farming systems largely depend upon two things: preservation plus production. A system must be productive enough to keep the farmer from abandoning. However, production must be maintained and enhanced in a way that is simple, affordable, and preserves the resources upon which this production is based. In short, a system that either falls short of the farmers’ needed production or a system that produces well but erodes the resource base is non-sustainable. The law which states that inputs need to be greater than or equal to outputs in a farming system calls to mind that unnecessary outputs, such as soil erosion and burning of organic matter, need to be minimized while affordable and sustainable sources of inputs need to be sought and added. One of the major sources of unnecessary nutrient outputs from systems is soil erosion. Soil erosion control needs barrier and cover consideration. A barrier along the contour is needed to reduce the surface flow of water, which is the carrier of loosened soil particles. A cover on the soil surface is needed to absorb the energy of the rain’s impact, which is the initiator of the erosion process. This book expounds NFPs as the best barrier and cover combination because of the added benefit of nitrogen fixation. Moreover, NFPs are valuable to all types of farming systems. As animal feeds, they are an excellent source of protein compared to grasses and non-nitrogen fixers. In reforestation schemes they are excellent recovery species on degraded lands by acting as their own “fertilizer factories,” making useful nitrogen out of atmospheric nitrogen. In crop and fruit production systems, NFPs can help hold the soil as contour hedges during establishment and provide an inexpensive source of nitrogen rich organic biomass mulch to be applied to the base of the crops and fruit trees. Thus, the title of this book, SALT: Nitrogen Fixing 47 Agroforestry for Sustainable Soil and Water Conservation, will serve as the parting thought. We should be in tune to the potential of nitrogen fixing agroforestry. We should try to view farming systems through a nitrogen fixing paradigm which acknowledges and makes use of this wonder of nature: the nitrogen fixing plant. It’s time to “catch the spirit” of NF agroforestry. For more information about nitrogen fixing agroforestry and in particular the Sloping Agricultural Land Technologies, contact or visit the Mindanao Baptist Rural Life Center. Project address: Mailing address: Kinuskusan, Bansalan, Davao del Sur P.O. Box 80322 8000 Davao City PHILIPPINES We will be glad to share our experiences and ideas with you and are eager to hear your experiences. 48 VII) REFERENCES USED AND FOR FURTHER READING Bunch, R. (1997) ECHO Development Notes, Issue 58, November. International Institute of Rural Reconstruction. (1989). Agroforestry technology information kit. IIRR, Silang, Cavite. Laquihon, W.A., D.S. Laquihon, , and J.S. Laquihon. (1996) Performance of Dairy Goats fed with Concentrate and Forage Legumes in Sloping Agricultural Land Technology (SALT) Farm. Proceedings of the Food and Fertilizer Technology Center (FFTC), Taiwan, Department of Agriculture (DA), Philippines, and Asian Rural Life Development Foundation (ARLDF) Philippines, sponsored seminar/workshop on Crop-Livestock Integration in Asian Sloping Lands held in Davao City, Philippines o September 3-5, 1996. 25 pgs. Lundgren, B. (1982). Introduction [Editorial]. Agroforestry Systems 1, 3-6. As cited in Young, “Agroforestry for Soil Management.” MacDicken, K.G. (1994). Selection and management of nitrogen fixing trees. Winrock International, USA, and Food and Agriculture Organization, Bangkok, Thailand. MBRLC Editorial Staff, ... MBRLC, Kinuskusan, Bansalan, Davao del Sur. Mindanao Baptist Rural Life Center. For the following publications: How To Farm Your Hilly Land Without Losing Your Soil: Sloping Agricultural Land Technology, SALT 1. 1991 Edition. 24 pp. How To Series No. 1 How To Make FAITH (Food Always In The Home) Garden In Your Homeyard. 1987 Edition. 21 pp. How To Series No. 2 How To Farm Better. 1989 Edition. How To Series No. 3 How To Raise Goats. 1991 Edition. 67 pp. How To Series No. 4 How To Raise Ducks for Food and Profit. 1988 Edition. 44 pp. How To Series No. 5 Simple Agro-Livestock Technology (SALT 2) Sustainable Agroforest Land Technology (SALT 3) Sloping Agricultural Land Technology (SALT) Test Results. Testing and Development Divison. 31 pp. 49 NFT Highlights: A publication of the Nitrogen Fixing Tree Association 1010 Holomua Road, Paia, Hawaii 96779-6744, USA. Partap, T. and Watson, H.R. (1994). Sloping Agricultural Land Technology (SALT): A regenerative option for sustainable mountain farming. ICIMOD Occasional Paper No.23. Kathmandu, Nepal: International Centre for Integrated Mountain Development. Watson, H.R. and Laquihon, W.A. 1985. Sloping Agricultural Land Technology (SALT): A Social Forestry Model in the Philippines. Found in: Rao, Y.S., Hoskins, M.W., Vergara, N.T., Castro, C.P., ed. Community Forestry: Lessons from Case Studies in Asai and the Pacific Region. Regional Office for Asia and the Pacific (RAPA) of the Food and Agriculture Organization (FAO) of the United Nations, Bangkok and Environment and Policy Institute, East-West Center, Honolulu, Hawaii, USA, 21-44. Young, A. (1989). Agroforestry for soil conservation. UK: CAB International. Young, A. (1997). Agroforestry for Soil Management, 2nd Edition. UK: CAB International, 320 pgs. 50 VIII) APPENDICES Appendix 1 - Commonly Used NF Plants in the Southern Philippines. (Some of the information in the following database was obtained from the sources listed below.) Awang, K. and Taylor, D.A., eds. (1993). Acacias for rural, industrial, and environmental development. Proceedings of the secdon meeting of the Consultative Group for Research and Development of Acacias (COGREDA), held in Udorn Thani, Thailand, February 15-18, 1993. Bangkok, Thailand: Winrock International and FAO. 258+ v pp. Bailey, L.H. (1929-1930). The standard cyclopedia of horticulture. The Macmillan Company, New York. Community forestry: some aspects. (1983). Regional Office for Asia and the Pacific (RAPA), Regional Forestry Economist, FAO of the UN, Bangkok, Thailand. Evans, D.O. and Szott, L.T. (1995). Nitrogen fixing trees for acid soils. Nitrogen Fixing Tree Research Reports (Special Issue). Winrock International and NFTA, Morrilton, Arkansas, USA. Evans, J. (1992). Plantation forestry in the tropics, Second Edition. Oxford University Press, Great Britain. Hensleigh, T.E., and Holaway, B.K., eds. (1988) Agroforestry species for the Philippines. U.S. Peace Corps, Washington, D.C. Horne, P.M., MacLeod, D.A., and Scott, J.M., eds. Forages on red soils in China: proceedings of a workshop. Lengshuitan, Hunan Province, PRC. 22-25 April 1991. ACIAR Proceedings No. 38, 142 p. Hubbell, D.S.(1965). Tropical agriculture an abridged field guide. Published by World Farming-Agricultura de las Americas-Farm Science Library. Copyright by Howard W. Sams International Corporation. Kansas City, Missouri, USA. International Institute of Rural Reconstruction. (1989). Agroforestry technology information kit. IIRR, Silang, Cavite. Kumar, Sri. S.V., I.F.S. and Bhanja, Sri. M., I.F.S. (1992). Forestry seed manual of Andhra Pradesh. Research and Development Circle, Andhra Pradesh Forest Department, Hyderabad. MacDicken, K.G. (1988). Nitrogen fixing trees for wastelands. Regional Office for Asia and the Pacific (RAPA), Food and Agriculture Organization of the UN, Bangkok, Thailand. McIlroy. (1972). An introduction to tropical grassland husbandry, Second Edition. Oxford University Press. National Research Council. (1984). Leucaena: promising forage and tree crop for the tropics. Second Edition. National Academy Press, Washington, D.C. National Research Council. (1983). Calliandra: a versatile small tree for the humid tropics. National Academy Press, Washington, D.C. NFTA. (1987). Proceedings of a workshop on biological and genetic control strategies for the leucaena psyllid. A special edition of “Leucaena Research Reports.” Volume 7(2). Honolulu, HI. Nitrogen fixing trees - a training guide. (1987). RAPA, FAO of the UN, Bangkok, Thailand. Ochse, J.J., Soule, M.J., Jr., Dijkman, M.J., and Wehlburg, C. (1961). Tropical and subtropical agriculture, Vol. 1. The Macmillan Company, New York. Patnaik, L.K., Egneus, H., and Das, S.S., eds. (1989). Social forestry handbook for Orissa. Vol 2 (Annexes). Bhubaneshwar. Resource book on sustainable agriculture for the uplands. (1990). MBRLC, Mag-uugmad Foundation, Inc./World Neighbors, IIRR. Philippines. Turnbull, J.W. (1986). Multipurpose Australian trees and shrubs: lesser-known species for fuelwood and agroforestry. ACIAR Monograph No. 1, 316 p. Australian Centre for International Agricultural Research, GPO Box 1571, Canberra, A.C.T. 2601. Tropical legumes: resources for the future. Report of the Ad Hoc Panel of the Advisory Committee on Technology Inbnovation, Board on Science and Technology for International Development, Commission on International Relations, National Research Council. National Academy of Sciences, Washington, D.C. 1979. 51 52 53 54 55 Appendix 2 - Leguminous and Nitrogen Fixing Species Tested and Used by MBRLC. Acacia angustissima Acacia auriculiformis Acacia confusa Acacia mangium Aeschynomene villosa Aeschynomene americana Albizia saman (formerly Samania) Albizia chinensis Albizia lebbeck Albizia procera Alnus nepalensis Arachis pintoi Arhidendron scutiferum Caesalpinia sappan Calliandra calothyrsus Calliandra haematocephalla Calliandra tetragona Cassia fistula Cassia nodusa Cassia pilusa Cassia ratondafolia Cassia siamea Cassia spectabilis Centrosema acutifolium Clitoria ternatea Crotalaria juncae Dalberia spruciana Dendrolobium umbellatum Desmanthus virgatus Desmodium heterocarpon Desmodium heterophyllum Desmodium intortum Desmodium ovalifolium Desmodium prenglie Desmodium salicifolium Enterolobium cyclocarpum Erythrina poepiggiana Flemingia macrophylla Flemingia (local-Philippines) Flemingia (local-Thailand) Gliricidia sepium Indigofera anil (tyesmani) Leucaena diversifolia Leucaena hybrid kx2 composite Leucaena hybrid kx3 composite Leucaena kx3a mix composite 56 Leucaena lanceolata (k393) Leucaena leucocephalla Leucaena leucocephalla hybrid kx1 Leucaena leucocephalla (k584) Leucaena macrophylla Leucaena pallida (k376) Leucaena pallida (k817) Leucaena pulverulenta Leucaena retusa Leucaena shannonii Parkia roxburghii Peleostigma malabaricum Pettrophorum pterocarpum Phacelya Saga adennanthera Sambacus nigra Sesbania aculeata Sesbania formosa Sesbania grandiflora Sesbania sesban (812) Stylosantes guianensis Stylosantes lamata Stylosantes scabra Tephrosia candida Tephrosia vosella Appendix 3 - MBRLC Rainfall Records, 1992 - 1995. RAINFALL MONITORING RECORD MBRLC, in mm (Monthly Summary) Date JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC YEARLY TOTAL 1992 12.70 0.00 0.00 55.88 107.95 165.10 297.18 248.92 99.06 369.57 104.14 69.85 1,530.35 1993 93.98 22.86 144.78 68.58 71.12 233.68 256.54 330.20 439.42 365.76 106.68 193.04 2,326.64 1994 104.14 0.00 157.48 248.92 297.18 502.92 124.46 607.06 73.66 12.70 177.80 154.94 2,461.26 1995 111.76 180.34 71.12 137.16 259.08 327.66 414.02 365.76 342.90 414.02 114.30 63.50 2,801.62 Total 322.58 203.20 373.38 510.54 735.33 1,229.36 1,092.20 1,551.94 955.04 1,162.05 502.92 481.33 Average 80.65 50.80 93.35 127.64 183.83 307.34 273.05 387.99 238.76 290.51 125.73 120.33 2,279.98 MONTHLY AVERAGE 127.53 193.89 205.11 233.47 190.00 57