Agronomic Benefits of Neem Coated Urea

See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/309384701 Agronomic Benefits of Neem Coated Urea – A Review Technical Report · October 2016 DOI: 10.13140/RG.2.2.10647.98722 CITATIONS READS 0 1,153 1 author: Bijay Singh Punjab Agricultural University 225 PUBLICATIONS 3,594 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: Fertilizer nitrogen management in wheat using a decision support system View project ICAR National Professor Project on need based and site-specific nitrogen management in rice and wheat View project All content following this page was uploaded by Bijay Singh on 23 October 2016. The user has requested enhancement of the downloaded file. All in-text references underlined in blue are added to the original document and are linked to publications on ResearchGate, letting you access and read them immediately. Agronomic Benefits of Neem Coated Urea – A Review Bijay Singh Punjab Agricultural University, Ludhiana 141 004, Punjab, India Email ID: [email protected] Executive summary Urea constitutes about 82% of the fertilizer nitrogen (N) used in India. Nitrification inhibitors when applied along with urea reduce losses of applied N thereby resulting in improved yield of crops. In early 1970s, it was observed that oil extracted from the seeds of neem (Azadirachta indica A. Juss), a tall perennial tree growing widely in the tropics and subtropics, and the cake left after oil extraction possess nitrification inhibition properties. Since then more than 75 studies have been conducted to compare the performance of urea coated with neem cake (NCU) or neem oil (NOCU) in increasing the yield of rice, wheat, and several other crops vis-à-vis uncoated urea. In 2015, the Government of India directed that all fertilizer urea manufactured in the country or imported will have to be coated with neem oil at the rate of 0.5 kg per tonne. This decision was motivated not only by the better performance of NOCU vis-à-vis uncoated urea, but also by an expectation that it will lead to reduced consumption of urea. As a side effect, NOCU is also expected to prevent industrial uses of subsidized urea intended to be used in agriculture only. Based on research published in peer reviewed journals, the present review attempts to assess agronomic benefits of replacing urea with NOCU in terms of increased crop production and/or reduced demand for fertilizer N in India. Depending upon the concentration of triterpenoids or neem bitters, the active nitrification inhibitor compounds, neem cake, extract or oil have been used in different quantities to coat urea. Although mean increase in the grain yield of rice and wheat by applying NCU/NOCU was around 5 to 6 % over the yields obtained by urea at same N level, in about 30% comparisons no increase was observed. As observed increase in yields have been obtained in researcher’s plots, the yield benefits of using NOCU should be considerably less when managed by farmers. Same applies to other crops such as sugarcane, cotton where also respectively, 8.7 and 4.3 % increase in yields have been recorded in researcher’s plots. There is large variation in fertilizer N rate for different crops depending upon land holding size, whether crop is irrigated or unirrigated and also because some farmers are accustomed to use heavy doses of fertilizer N. According to principles of fertilizer evaluation, the difference between the performances of the two sources narrows down at high application rates. Further, the nitrification inhibitors perform better in irrigated than in rainfed crops and in acidic soil conditions than in neutral and alkaline soils. As more than 50% of the total urea consumed in India is applied to rice and wheat, and more than 30% is applied to rainfed crops, overall impact of coating all urea supplied to farmers with neem is likely to be small. With same general recommendations for managing urea and NOCU, a reduction in demand in fertilizer N cannot be expected. A perception that when farmers will get higher yields they will reduce the dose of NOCU as compared to urea may not work if the yield gains due to replacing of urea with NOCU are small and many a times not visible. Also, farmers will not readily cut down the fertilizer dose to avoid any risk for obtaining lower yields. Possibly, applying NOCU following the site-specific nutrient management principles will lead to production of yield levels higher than or similar to that obtained with untreated urea but with lower rates of application. 6 Million tonnes (Mt) in 1965-66 to 16. India has emerged as the second largest consumer of N in the world. Most notable two broad categories of transformations are: (i) hydrolysis of urea by urease enzyme which rapidly converts urea-N to ammonium-N and (ii) nitrification brought about by a group of nitrifying bacteria that leads to conversion of ammonium-N to nitrate-N. The oil extracted from the seeds of neem (Azadirachta indica A. the Government of India allowed urea manufacturers to coat granular urea with neem oil to produce NOCU up to 35 % of total capacity of their plants. Quality assurance of the neem cake coated urea was another problem. of which some are susceptible to loss and therefore lead to reduced availability of N to crop plants.5 kg neem oil is needed per tonne of urea and (ii) the N content in urea meets the Fertilizer Control Order standards (Prasad et al. urea is the major source of fertilizer-N. Africa.2 t neem cake per tonne urea. coating urea with neem cake manually or in factories did not turn out to be practically feasible on a large scale. has no storage risks and can be used for all types of crops and soils with little or no harm to the soil. Although some nitrification inhibitors are available. While urea provides the most N at the lowest cost. Some chemicals categorized as nitrification inhibitors temporarily delay/inhibit the bacterial oxidation of the ammonium-N by depressing over a certain period of time (4 to 10 weeks) the activity of Nitrosomonas bacteria in the soil. In March 2015. Thus nitrification inhibitors control the loss of nitrate by leaching and/or denitrification from the topsoil by keeping N in the ammonium form longer and thereby increasing the fertilizer N use efficiency and yield of crops. With NOCU already being supplied to farmers as fertilizer N in India. Nitrification inhibiting property of neem and its role in increasing urea N use efficiency in rice was first reported in early 1970s (Bains et al.1 % fertilizer-N was consumed as urea in 2014-15 (FAI. When urea is applied to the soil. This decision was motivated not only by the better performance of NOCU vis-à-vis uncoated urea in terms of crop production.95 Mt in 2014-15.5 Mt in 2015-16. ammonium-N is susceptible to loss via ammonia gas. 2015). neem cake was used for coating of urea. but also by an expectation that it will lead to reduced consumption of urea. In most of the studies conducted up till 1990.1–0. Both the oil and the cake can be used to coat urea for increasing urea N use efficiency in cropping systems. Juss). Neem cake coated urea (NCU) was produced either manually on a small scale or in factories by mixing 0. With record urea production of 24. it is not yet clear as to what Agronomic Benefits of Neem Coated Urea – A Review 2 . a tall perennial tree growing widely in tropical and subtropical areas of Asia. controlling the losses of urea-N should lead to increased crop productivity. and the cake left after oil extraction possess nitrification inhibition properties. use efficiency of urea-N by different crops can be as low as 20% and it rarely exceeds 50%. these are expensive and farmers in countries like India cannot yet afford these. and nitrate-N can escape soil-plant system through leaching below the rooting zone and in gaseous forms via denitrification leading to reduced fertilizer N use efficiency.. 2002). its dominance as source of fertilizer N in India is likely to continue. Therefore neem oil as an alternative to neem cake has been used to coat urea granules to retard nitrification of ammonium-N in the soil. the government made it mandatory for fertiliser firms to produce NOCU up to 70 % of capacity and finally in May 2015 directed to manufacture full capacity. Although promising results in terms of increased crop yields were obtained. The neem oil coated urea (NOCU) has two advantages: (i) only 0. 1971). a cascade of chemical and biological reactions transform urea- N into several other N forms. America and Australia (Schmutterer. On the basis of the performance of NCU and NOCU in studies carried out with several crops in different parts of the country.. 1990). Although plants can use both ammonium-N and nitrate-N with equal ease. From an agronomic perspective.Introduction With consumption of fertilizer-nitrogen (N) increasing from 0. 83. Since 1970s. . 1980) in which a coal tar-kerosene solution (100 g/200 ml) was used to stick neem cake powder on to urea. when ripe. Neemex (Agro Extracts Ltd. These are slightly hydrophobic but freely lipophilic and highly soluble in organic solvents like alcohols and esters. a yellowish sweet pulp that encloses a brown seed kernel. Variants of neem coated urea After Bains et al. valassin and their derivatives (Schmutterer. its composition changes with the raw material used for the oil extraction. 80. In India.extent it will lead to increased food production and/or reduced demand for urea. lateritic and shallow black soil at altitudes less than 500 m above sea level (as in central and southern India) were richer in triterpenoids than the ecotypes growing at higher altitudes and on alluvial soils in hot and cold climates (northern and western India). As for neem oil. the finished product contained only 35% N because fairly large amount (20% w/w of NCU) of neem cake was required to achieve desirable coating level. several commercial neem based products were developed and marketed in India. (1971) reported the nitrification inhibition properties of acetone extract of dried and finely ground neem kernels. and were reasonably successful. 2012). NCU was prepared following this technique. In most of the field experiments conducted during last three decades. Reddy and Prasad (1975) coated urea with neem cake by moistening the urea lots with acetone (25 ml kg-1 urea) and thoroughly mixing with powdered neem cake (200 g kg-1 urea). Fruits are the major source of compounds that can inhibit nitrification in the soil. 1990). gedunin. nimbin. Nimin containing at least 5% triterpenes (Godrej Agro Pvt. Nimin with ensured higher Agronomic Benefits of Neem Coated Urea – A Review 3 . Tignic acid in neem seeds imparts distinctive odour to neem oil (Schmutterer.. Bangalore) and Ralli Neem (Naturelle Biotech Ltd. meliacin. neem oil and neem cake Neem is an evergreen. Mumbai) (Vyas et al. research investigations based on scientifically-sound experiments and published in peer- reviewed journals have been critically analyzed to better understand the agronomic benefits of neem coated urea vis-à-vis ordinary urea. fast-growing tree belonging to the family Meliaceae (ord. Rengasamy et al. Nicoletti et al. After noticing the promising performance of NCU under field conditions and limitations associated with its preparation. Later a more efficient technique of coating urea with neem cake was developed (Sharma and Prasad.. Three such products. However. Sapindales).000 tons of oil and 330. 2012). Also. 1995. Quality and composition of neem oil can vary according to the origin of the raw material and the different oil extraction processes. slanin. Neem. the concentration of triterpenoid in neem oil changes with the geographical area and the season in which seed are harvested (Ermel. For example. this practice did not attract farmers mainly due to cumbersome methodology and lack of ready availability of raw materials at farm level. embedded in a hard white shell. Neem cake is the final by-product of oil extractions from neem kernels and also contains substantial amounts of triterpenoids. 1990). Therefore. 2012). Hyderabad) were based on extracts of neem seeds and/or neem cake and industrial-grade neem oil. Neem oil is obtained by cold-pressing neem seeds followed by extraction with organic solvents (Nicoletti et al. Ltd. These compounds belong to natural products called triterpenoids or limonoids and constitute the bitter principles of neem seed oil. (1996) observed that the neem ecotypes growing in regions with moderate climate and in red. Fruits of neem are produced in drooping panicles and have.1991).000 tons of neem cake are produced annually from 14 million naturally growing trees (Nicoletti et al. Sridharan and Venugopal (1998) observed a negative influence of total rainy days during fruiting season (April to August) on the content of triterpenoids and a significant positive influence of sunshine hours during off-season (September-March) on the oil content in neem seeds. Biologically active principles isolated from neem seed include azadirachtin.... Suresh et al.0 to 30.5 kg neem oil per tonne of urea which was acceptable to fertilizer industry. However. nonstandard nature and bulkiness of the NCU. Kumar et al. Purkayastha et al. In wheat. 2000). Tiwari. 1989. NOCU as an industrial product was conceived in late 1990s.9%. Efficiency of NOCU vis-a-vis urea in terms of nitrification inhibition can also be gauged from reduced emission of N2O and nitrate leaching. This technique required only 0. 1997. (2008) reported that NOCU prepared from expeller grade neem oil was consistently superior to that derived from hexane extracted oil. 2010). Kumar et al. it was the 1... And in the second year. Majumdar (2005) observed that Nimin coated urea could substantially conserve soil ammonium and was inferior only to DCD when applied to rice.. In a meta-analysis based on 113 data sets from 35 field studies (Akiyama et al.5 or 2 g neem oil kg−1 urea. Kumar et al. Majumdar et al. 2002).. 1999). Nimin coated urea inhibited nitrification better than urea +DCD (Majumdar et al. the 0. Inhibition of nitrification due to coating of urea with neem cake has been reported by a number of researchers (Misra and Chhonkar..0 g neem oil kg−1 urea. 0. Suitable nozzles and other equipment for coating urea at the factory as a small appendage to the existing urea plants were also developed (Suri.small quantities of urea were mixed by hand and for large quantities rotary mixers were used. Suri et al. Nitrification inhibition/retardation in soils treated with neem cake or oil coated urea In several studies. In the first year. Reddy and Prasad (1975) found that 2 weeks after incubation NCU was only 50% as effective as Nitrapyrin in retarding nitrification in the soil. Kumar et al. Thomas and Prasad (1983) observed that in five different soils the performance of NCU was inferior to that of Nitrapyrin. Chauhan. 2003). (2007) found that cold pressed and expeller grade neem oils were the best for the production of NOCU. Malla et al. which was significantly better than the 0. (2005) found that NOCU and DCD were equally effective in rice but NOCU was more effective than NCU.5 mg neem oil kg−1 urea was not significantly different from the uncoated urea. (2000) found that total N2O emission from both Nimin coated urea and NCU applied to rice was not significantly different from untreated urea. An Indian patent was secured for producing NOCU using this process (Saxena et al. Considering the poor shelf-life. 1995. while DCD and nitrapyrin could reduce N2O emission observed with conventional fertilizer by 38 and 50%. To prepare neem coated urea. Subbiah and Kothandaraman. It suggests that NOCU produced by fertilizer plants by coating 0.. (a nitrifying bacteria) under field conditions in a sandy clay soil under rice to which N was applied as NCU rather than ordinary urea. 1997. (2007) observed that percent nitrification inhibition of different NOCUs prepared with various neem oils ranged from 4. DCD was more effective than both NOCU and NCU which were at par. But when applied to wheat. 1999).concentration of triterpene than neem cake was the most successful among these. In another study. 1978. these products depending on triterpene content were thoroughly mixed with urea to obtain a uniform coating . (1995) observed a significantly lower population of Nitrosomonas sp.5 kg neem oil per ton of urea may not perform adequately under all situations. (2010) conducted field experiments to investigate the optimal load of neem oil in enhancing agronomic efficiency of NOCU in lowland irrigated rice. extent of nitrification inhibition associated with NCU or NOCU has been compared with well proven nitrification inhibitors such as DCD (dicyandiamide) and Nitrapyrin [2-chloro-6-(trichloromethyl) pyridine]. the effectiveness of NOCU. and lack of standardization encountered when different neem extract-neem oil emulsions were hand mixed by farmers. NCU and Nimin coated Agronomic Benefits of Neem Coated Urea – A Review 4 . Micro-emulsion was developed using industrial grade neem oil with Bureau of Indian Standards specifications. 1980. and right type and proportion of emulsifier to coat urea prills were defined (Prasad et al. Blaise and Prasad. Agronomic performance of NCU.2 % with only 3 negative values. and crops other than rice and wheat are reported in the following sections. (1993. Table 1. About 60% of all the published research papers to evaluate NCU/NOCU vis-à-vis urea have used rice as the test crop.4 4. wheat.7 Prasad and Prasad (1980) Agronomic Benefits of Neem Coated Urea – A Review 5 . Wherever insignificant difference between the two sources was reported. Table 1 also includes results from several recent studies and from a few more publications not included by earlier reviews. rice-wheat system. As performance of NCU. (1993) reported a rice yield increase in the range of -26. Per cent increase in yield of rice and nitrogen use efficiency by applying different variants of neem coated urea over untreated urea Neem Coating thickness Location Per cent Difference Reference coated increase in between per urea grain yield cent recovery product† over that efficiency of N obtained applied as neem with urea¶ coated urea and uncoated urea§ NCU 20% neem cake New Delhi 11.5%.9 Reddy and Prasad (1977) NCU 20% neem cake New Delhi 5.2 g neem cake per g urea had no effect on loss of 15N-labelled urea (John et al. Rice More number of experiments to compare different variants of NCU with urea have been conducted with rice than other crops like wheat. although NCU and urea did not differ significantly but there was an increase in yield of rice obtained with NCU as compared to urea. 2007). in 18 instances there was no significant difference between the performance of urea and different variants of NCU. Prasad et al (2007) worked out average increase in grain yield due to application of NCU/NOCU over urea to be 8.urea was only 14%. The positive values ranged from 0. it suggests that there is a 30% probability of registering no increase in yields when urea is replaced with NOCU for supplying N to rice.9 to 54. per cent yield increase should be taken as no increase.1 2. 2007). And more than 40% of the studies on rice have been carried out at Indian Agricultural Research Institute.. it has been listed as ‘no increase’ or 0 %. Coating urea with 0.2% with an average value of 9. Out of 55 comparisons listed in Table 1. 1989). maize or sugarcane. Besides all the publications cited by Prasad et al. The data as compiled in Table 1 lists results reported in 48 publications. Prasad et al.6%. In such cases. Nimin coated urea or NOCU in increasing yield of rice was almost similar. Nimin coated urea or NOCU in terms of per cent increase in the yield of rice over that obtained with urea at the same N level has been reviewed by Prasad et al. Neem coated urea vis-à-vis urea: Effect on crop yields After nitrification inhibition properties associated with neem cake were demonstrated during early 1970s. performance of NCU/NOCU vis-à-vis urea has been evaluated in more than 75 field experiments conducted with different crops all over India. New Delhi. only 17 research papers were published which evaluated this material as a coating on urea granules. (1993. After 2000 when NOCU started becoming available.30 to 54. Results pertaining to evaluation of NCU/NOCU vis-à-vis urea for rice. In several research papers. About 60% of these studies used NCU and were conducted up to 2000. Singh and Singh (1991) NCU 20% neem cake Bhubane. (1991) NCU 20% neem cake Aduthurai 15.7 . John et al. (1990) NCU 20% neem cake Pantnag-ar .3 . (1990) NCU 20% neem cake Varanasi 7. Latha and Subramanian (1986) NCU 20% neem cake Thanjav-ur 30.4 Sharma and Prasad (1980) NCU 20% neem cake New Delhi No increase 13.0 Pandey and Singh NCU 20% neem cake Dholi 11. (1999) NOCU 0. (2001) NOCU 0. (1998) NCU 20% neem cake Faizabad 13. Awasthi and Mishra (1987) NCU 20% neem cake New Delhi No increase . No increase ore NCU 20% neem cake Pusa 16.4 .8 Shivay et al.2 . 4. (2001) Agronomic Benefits of Neem Coated Urea – A Review 6 . Budhar et al.4 . Shukla and Chauhan (1998) PNGU 12% neem oil New Delhi 7.0 NCU 20% neem cake New Delhi 4.4 (1987) NCU 20% neem cake Pantnag-ar 18.7 . Sinha et al. Prasad et al. Prasad et al. Prasad et al.NCU 20% neem cake Dholi 15.5 .1 .4 . Prasad et al. Singh et al.2 . (1989) NCU 20% neem cake Philippin-es No increase .1 . Mahapatra et al. (1990b) NCU 20% neem cake Vellanik. (1999) Nimin 1% Nimin Cuttack No increase Rath et al. Singh et al.5 . (1990) kara NCU 20% neem cake Faizabad 24. Panigrahi and Dixit swar (1991) NCU 20% neem cake Pusa No increase Mishra et al. (1989) (1986) 7.7 .2 . No increase .0 .4 (1987) 15. (1987) NCU 20% neem cake Coimbat. (1991) Nimin 1% Nimin Raipur No increase Pandey and Tripathi (1994) Nimin 1% Nimin Kota 16. Tomar and Gupta (1996) PNGU 12% neem oil New Delhi 36.5 kg neem oil t-1 New Delhi 9. Thomas and Prasad (1987) NCU 20% neem cake Aduthurai No increase Velu et al. (1987) NCU 20% neem cake Coimbat.5 kg neem oil t-1 New Delhi 12. 9. Singh et al. 3. Govindasamy and Kaliyappa (1986) NCU 20% neem cake Pantnag-ar No increase .1 Mishra et al.0 . Budhar et al. Joseph et al. (1987) ore NCU 20% neem cake Smastip-ur 5. Agarwal et al.5 . Surve and Daftardar (1985) NCU 20% neem cake Coimbatore No increase . (1980) NCU 20% neem cake New Delhi 14. (1984) NCU 20% neem cake Rahuri 54.0 . (1990a) NCU 20% neem cake Kanpur 5.5 Prakasa Rao and Prasad (1982) NCU 20% neem cake New Delhi 11.0 19.3 11. 30.2 Kumar et al.6 . respectively Average increase in yield obtained by applying NCU to rice in 55 comparisons is 8.YU) / YU. Agronomic Benefits of Neem Coated Urea – A Review 7 . (1998). (2010b) splits). Singh and Singh (1991).5 kg neem oil t-1 Modipur.9 Kumar et al. NOCU –Neem oil coated urea (0. 36% at New Delhi. (2012) urea) -1 Nimin 1% Nimin Kandha.4% increase observed with DCD from 6 observations from 4 studies. Sannagoudra et al. 29% at New Delhi) recorded by Surve and Daftardar (1985). 6.5 (using using LCC) LCC) NCU 20% neem cake 5 on-farm 1.4.2% at Rahuri.8 Jat and Pal (2002) am NOCU 0. mal (2015) †NCU-Neem cake coated urea (200 g neem cake powder kg-1 urea).6 Singh and Shivay NCU 20% neem cake New Delhi No increase 4. when five abnormal increases in yield (54.6 (using LCC) (using LCC‡) NOCU 0.5% at Thanjavur. Kumar and Shivay (2009) NOCU 0.1 Thind et al. Prasad et al.. Prasad et al.0 10.0 8. PNGU – Pusa neem golden urea (urea-neem oil adduct containing 35% N and 12% neem oil). 7.5 kg neem oil t-1 Ludhiana 5.3% with a range of values between 0 and 18. (2010) were excluded.3 . and Kumar et al.5 kg neem oil t-1 New Delhi No increase .6 (3 3.UU) / F. (2011) NCU 30% neem cake Dharwad 9. 7. However. 2013).6 11.9% over the yield produced by applying urea. Govindasamy and Kaliyappa (1986). In a meta-analysis using data extracted from the literature where the effect of nitrification inhibitors on rice yield or plant N uptake was compared in side-by-side field experiments to an identical fertilizer without nitrification inhibitor (Linquist et al. (2007).5 kg neem oil t-1 urea).5 kg neem oil t-1 9 on-farm 9. NCU produced about 8% higher yield of rice as compared to 6. No increase . (2007) Nimin 1% Nimin Mymens. Nehra and Dhindwal (Haryana) (2010) NOCU 0.0 - NOCU 0. where YN and YU represent yield of rice obtained by applying neem coated urea and uncoated urea at same N level. NOCU 500 ml (100 kg Dharwad No increase . where F represents the N level. and UN and UU represent N uptake by rice by applying neem coated urea and uncoated urea.4 (3 splits). NOCU 0. 3.5 kg neem oil t-1 New Delhi No increase 5. Kumar et al. (2001) sites in Delhi NOCU 0. 24.5 kg neem oil t-1 New Delhi 12. (2010) NOCU 1.9 Mohapatra et al.8 13.8 (2003) PNGU 12% neem oil New Delhi 10. based on 22 observations from 9 studies. the average increase turned out to be 6. Kumar et al. Nimin – a blend of neem oil and neem seed extract ‡site specific N management using leaf colour chart ¶ 100 × (YN . respectively § 100 × (UN .7% at Faizabad. 8.0 kg neem oil t-1 New Delhi 29.3 Nimin 1% Nimin New Delhi No increase No increase Majumdar (2005) PNGU 12% neem oil New Delhi 12.7 .5 kg neem oil t-1 Gurdasp-ur No increase No increase (3 (3 splits or splits).1 .1 . Hoque and Sultana ingh (2008) PNGU 12% neem oil New Delhi 15. Kumar and Prasad (2004) NCU 20% neem cake New Delhi 9. 1991. fine-textured soils are less susceptible to this form of N loss. 2008). the per cent increase in wheat grain yield ranged from 4. no difference between the two sources of N was observed in 2 out of 7 comparisons (Table 2). Kumar et al. lower nitrification rates as caused by nitrification inhibitor may reduce soil acidification. there is possibility that in more than 25% cases NCU may not outperform urea.6 to 23. (2010a) studied Agronomic Benefits of Neem Coated Urea – A Review 8 . 2008). NCU at the rate of 100 kg N ha-1 significantly increased the yield of rice. But at higher N level. Vyas et al. which in alkaline soils may result in a prolongation of an elevated pH and a consequent increase in ammonia volatilization (Kim et al. 2012).7. As soil texture is one of the most important factors affecting losses through nitrate-N leaching. Budhar et al. use of nitrification inhibitors in these soils can induce the losses as ammonia further due to the increased residence time in the soil. In the 5 comparisons where NCU performed better than urea. In a meta-analysis on the effect of nitrification inhibitors on crop productivity and N use efficiency (Abalos et al. (2014).. application of nitrification inhibitors to neutral and alkaline soils may increase N losses through ammonia volatilization thereby decreasing the overall effect of inhibitors on crop yield and N use efficiency in these soils. 2007.. Therefore. (2007) have reported this range as 3..Tomar and Verma (1990) observed nearly equal yield of rice with NCU at 80 kg N ha-1 as with urea at 120 kg N ha-1. a smaller effect size of nitrification inhibitors on crop yield was found for fine-textured soils compared to medium. increases in yields were not significant. In the meta-analysis carried out by Abalos et al. Wheat In six published works in which comparative performance of different variants of neem coatings on urea was studied vis-à-vis uncoated urea on wheat.. 1987. Kim et al. The opposite was true in case of neutral soils. it is not adequately supported by the published data. Shivay.. Ketkar (1974) could observe that on acid soils NCU at the rate of 50 kg N ha-1 significantly increased rice yield over that recorded with uncoated urea. De et al. Thind et al.3% and as in case of rice. Also. Thus based on 7 comparisons..or coarse-textured soils. It seems that because nitrification rates are favoured by neutral to slightly alkaline soils (Norton. but the increase in yield was not significant at lower levels of N application. 2008).8 %. (2008) found that NOCUs prepared with expeller grade or hexane extracted neem oils performed the best in coarse-textured soil and the worst in sodic soil. 2014). nitrification inhibitors could potentially be beneficial in these soils and at high N levels may reduce the net N losses via both nitrification–denitrification and ammonia volatilization. Mohapatra et al. where the risk of ammonia volatilization is greater (Francis et al. 2015). and Singh and Singh (1991) but in many studies positive effect of NCU on rice yield was not large enough (Panigrahi and Dixit. and the relatively small effect size of inhibitors for fine-textured soils is likely due to the fact that nitrate loss through leaching is less in these soils. (2012) showed that application of nitrification inhibitors may increase ammonia volatilization because ammonium-N remains in the soil for a longer period. (2010b) reported statistically similar yields of rice with 96 kg N ha-1 as NCU and 120 kg N ha-1 as urea in a coarse textured soil but not in a fine textured soil. (1992) concluded that more than 30 kg N ha-1 can be saved in rice with Nimin coated urea in comparison to untreated urea. Although Prasad et al. average increase in yield by applying NCU over that obtained with urea is 5. acidic soils (pH ≤ 6) showed a higher positive response to application of nitrification inhibitors than neutral (pH 6–8) and alkaline soils (pH ≥ 8). Thind et al. (1991) reported similar yields of rice with 70 kg N ha-1 in form of NCU as with 100 kg N ha-1 applied as uncoated urea. It is possible that nitrification inhibitors may be less effective in higher pH soils. Similar results have been reported by Awasthi and Mishra (1987).3 to 12. Since neutral to alkaline soils have inherently high losses through ammonia volatilization (Singh et al. Soil pH regulates efficiency of nitrification inhibitors via its effect on ammonia volatilization. (1991) and Singh et al. Coating Location Per cent Difference Reference urea thickness increase in between per product† grain yield cent recovery over that efficiency of N obtained applied as neem with urea¶ coated urea and uncoated urea§ NCU 20% neem Kanpur 5.1 Singh and Singh cake (1986) NCU 20% neem Pusa 5. no increase in yield of both rice and wheat was Agronomic Benefits of Neem Coated Urea – A Review 9 . (1981).1 7. Performance of NOCU at 96 kg N ha-1 drilled during sowing of wheat was better than urea or NOCU applied at 120 kg N ha-1 in 2 split doses in the sandy loam soil suggesting that while drilling NOCU could curb losses via ammonia volatilization. respectively § 100 × (UN . 4. (1991) cake NCU 20% neem New Delhi No increase 1. Sharma and Prasad (1978). However. the NOCU did not out-perform urea in increasing grain yield at any level of N application in both the soils. 96. NOCU –Neem oil coated urea (0. the nitrification inhibitor properties of NOCU helped in checking the nitrate leaching losses.5 kg neem oil t-1 urea). (1986) cake NCU 20% neem Pantnagar . where F represents the N level. Prasad et al. 5 reports published in 1999 and later reveal a different picture of the effect of NCU/NOCU in rice- wheat cropping system. Bhatia et al. Mishra et al. As listed in Table 3.3 . Only when NCU was applied to both rice and wheat. When nitrogen was applied in 2 equal split doses at the time of sowing and first irrigation. no consistent effect was observed by researchers (Table 3).YU) / YU. NOCU did not perform better than urea because loss of N via nitrate leaching was relatively small. Per cent increase in yield of wheat and nitrogen use efficiency by applying different variants of neem coated urea over untreated urea Neem.relative performance of NOCU vis-à-vis ordinary urea applied to wheat when applied at 48. In the fine textured soil.7 .3 . (2010a) t-1 †NCU-Neem cake coated urea (200 g neem cake powder kg-1 urea).5 kg neem oil Ludhiana No increase No increase Thind et al. Nimin – a blend of neem oil and neem seed extract ¶ 100 × (YN . Prasad et al. (1999) have reported that NCU applied to rice leaves a positive residual effect on the following crop of wheat grown in an annual rotation.4 . and 120 kg N ha-1 or drilled in between rows as a single dose of 96 kg N ha-1 in sandy loam and clay loam soils. (1990) cake NCU 20% neem Hisar 4. Table 2. respectively Rice-wheat system Reddy and Prasad (1977).3 NOCU 0.UU) / F. Chauhan (1999) could obtain significant yield increases in both rice and wheat over uncoated urea in two consecutive years. (1985) cake NCU 20% neem Pusa 12. where YN and YU represent yield of wheat obtained by applying neem coated urea and uncoated urea at same N level.1 Majumdar et al (2002) cake Nimin 1% Nimin New Delhi 9. Agarwal et al. In four out of the remaining seven comparisons. and UN and UU represent N uptake by wheat by applying neem coated urea and uncoated urea. Mishra et al. where YN and YU represent yield obtained by applying neem coated urea and uncoated urea at same N level. After rice and wheat. maize and finger millet by supplying N via NCU over urea works out to be 10. respectively Crops other than rice and wheat Comparative performance of NCU and urea for crops other than rice and wheat has not been studied by many researchers.3. Agronomic Benefits of Neem Coated Urea – A Review 10 . No increase No increase Bharde et al.YU) / YU. Location Year Per cent Per cent increase Reference urea increase in rice in wheat yield product† yield over that over that obtained with obtained with urea‡ urea‡ NCU Faizabad 1993.0 and 5. 24. NOCU –Neem oil coated urea (0. cotton. tomato and French bean. potato. very small proportion of total N consumed in India is applied to these crops. possibly because NCU/NOCU was applied to rice and residual effect was tested in wheat. sugarcane. a yield benefit only in rice was observed. However. Mean per cent increase in the economic yield of potato. 0. 2000 Bharde et al. No increase No increase 02 NOCU 9 on-farm 2006. No increase No increase Bhatt (2012) locations. Japanese mint. 9. PNGU – Pusa neem golden urea (urea-neem oil adduct containing 35% N and 12% neem oil) ‡100 × (YN . for sugarcane and cotton in one out of four comparisons and for maize in one out of three comparisons no significant increase in yield was observed by supplying N as NCU rather than urea. Table 3. The data available from published research papers are summarized in Table 4. 2008 Kapurthala †NCU-Neem cake coated urea (200 g neem cake powder kg-1 urea). No increase No increase 01 NOCU New Delhi 1999. (2003) PNGU New Delhi 2000. 24. 8. (2006).recorded by applying NCU over urea.51 24. jute.61 Chauhan (1999) 94 1994. Although better performance of NCU was also observed for finger millet.23 No increase Malla et al. 4. respectively. Per cent increase in yield of rice and wheat grown in annual rice-wheat rotation by applying different variants of neem coated urea over untreated urea Neem. cotton and maize are the crops to which significant amount of fertilizer N is applied. 10.5 kg neem oil t-1 urea). (2005) 02 NOCU New Delhi 2001. sugarcane.7. 14.4.42 25.5.24 No increase 01 NCU New Delhi 2001. In three instances.71 95 PNGU New Delhi 1999.09 No increase 2000 NOCU New Delhi 2000. 0 kg grain per kg N applied with a mean value of 2. Per cent increase in yield of different crops other than rice and wheat by applying different variants of neem coated urea over untreated urea Crop Neem. In a meta-analysis based on a global data set consisting of 21 studies with 94 observations (Abalos et al. respectively Neem coated urea vis-à-vis urea: N use efficiency Thind et al. urea in rice. It is calculated in units of yield increase per unit of nutrient applied. only four comparisons as listed in Table 2 are available.3. b) studied the performance of NOCU vs. In case of wheat.6 (80 kg N ha-1) NCU Palampur 16. (1980) NCU Pusa 10.2 Sivaraj and Iruthayaraj (1980) NCU Indore 6. (2008) Cotton NCU New Delhi No increase Sheshadri and Prasad (1979) NCU Coimbato-re 5. -------------------------------------------------------------- 1 Agronomic efficiency (AE) reflects the direct production impact of an applied fertilizer and relates directly to economic return. (2014) Maize NCU Ratlam No increase Joshi et al.1 kg grain per kg N applied.0 Yadav et al. (1990) NCU Coimbato-re 3. Data pertaining to measures of fertilizer use efficiency as listed in Table 5 show that while agronomic and apparent recovery efficiencies1 of both NOCU and urea decreased with increasing N rate. urea at three N levels in increasing N uptake and yield of rice and wheat in coarse and fine textured soils.0 Sharma et al. the mean effect sizes of widely used nitrification inhibitors [3. (1982) †NCU-Neem cake coated urea (200 g neem cake powder kg-1 urea) ‡100 × (YN . (1987) NCU Lucknow No increase Yadav et al.2 Singh et al. Apparent recovery efficiency (RE) is defined as the difference in nutrient uptake in above-ground parts of the plant between the fertilized and unfertilized crop relative to the quantity of nutrient applied. (2010a.7 Subbiah et al.8 Desai et al. Location Per cent increase in Reference urea yield over that product† obtained with urea‡ Potato NCU Simla 2. N uptake by the test crop was estimated (Table 1) so that the difference between per cent recovery efficiency of NOCU and untreated urea in rice could be estimated. It ranged from 0 to 19. Agronomic Benefits of Neem Coated Urea – A Review 11 . The difference between agronomic efficiency of NOCU and urea for 43 comparisons ranged from 0 to 11..87 Mani et al. (1986) Sugarcane NCU New Delhi 20. Only in 16 studies comparing NOCU/NCU vs. The data in Tables 1 and 2 suggest that NCU was able to supply N more efficiently than urea in rice than in wheat. 2014).3 with a mean value of 3.9 Parashar et al.8 (40 kg N ha-1) Sharma et al. these were higher for NOCU than for urea in the sandy loam soil but not in the clay loam soil.4. (1980) NCU Simla 12.Table 4. (1982) NCU Surat 5.4 with a mean value of 7.YU) / YU. where YN and YU represent yield obtained by applying neem coated urea and uncoated urea at same N level. (2014) Finger millet NCU Jobner 5.4-dimethylepyrazolephosphate (DMPP) and DCD] was about 11% increase in N use efficiency. (1989) NCU Coimbato-re 5. It may be mentioned here that both agronomic and recovery efficiency of N were determined by the rate of application of fertilizer N.1 Jain et al. Difference between per cent N use efficiency of NCU and that for urea ranged between 0 and 7. 2 and 4) should lead to more than 5% increase in the overall crop production. The corresponding rates of consumption of fertilizer N for marginal (< 1 ha).4.Table 5.8 27.3.3 †Agronomic efficiency. 30. 2015). at higher N rates the yield response to NOCU would be less pronounced because N rates may be above optimal and as such extent of positive response of crop yields may be minimal.7 kg). This trend is not expected to change substantially for next 2 to 3 years. respectively.9 30.2 66. wheat. small (1-2 ha).7 24.9 Urea.5 91.2 53.1 24.6 (kg N ha-1) against 119. 24.0 22.120 24.3.3 and 0%.8 20.3 58.7. medium (4-10 ha) and large (> 10 ha) holdings in irrigated areas were respectively. 2016). Agronomic and apparent recovery efficiency of urea and neem oil coated urea (NOCU) applied to rice and wheat grown in sandy loam and clay loam soils Source.3 21. 118.7 and 4. 110.0. 9. Agronomic Benefits of Neem Coated Urea – A Review 12 .3.9 21.8 20. the mean N use level was 128. kg Rice Wheat N ha-1 Sandy loam soil Clay loam soil Sandy loam soil Clay loam soil AE† RE‡ (%) AE RE (%) AE RE (%) AE RE (%) Urea.5 60.0 kg N ha-1) in unirrigated areas.48 29.8 70.9. per hectare N use in India is the maximum in wheat (119. wheat. 52.6 50. kg grain/kg N applied ‡ Apparent recovery efficiency of applied N Source: Thind et al. 2015).0 60. When all urea being supplied (produced indigenously as well as imported) for agricultural use has been replaced by NOCU in India. it needs to be taken into account that yield increases over urea listed in Tables 1.7 and 44.5 87. 4. 174. 48 28.4 kg N ha-1 in rainfed crops.7 19.7 kg ha-1) (FAI. 120 21. sugarcane.6.6 47. Thus farmers who are accustomed to use high and above optimal levels of urea-N in different crops may not observe significant improvement in yield levels by applying NOCU.9 % of total urea consumed in the country was applied to rice.0 Urea. 2 and 4 have been recorded from experiments conducted by researchers under optimum agronomic and plant protection management conditions available at research stations.0 21. Among cereals.4 25. Even the reported efficiency of urea in researcher’s plots is not achievable under on- farm trials supervised by researchers and extension workers because water.0. Dobermann et al.0 72.5 NOCU.4 52.3 20. sugarcane. As per the input survey for India for 2011- 12 (Anonymous.8 NOCU. 5. respectively (Tables 1. fertilizer and crop management level are rarely up to the mark. there is large variation in fertilizer N rates for different crops depending upon land holding size and whether crop is irrigated or unirrigated.9 kg N ha-1 in irrigated crops against 76. 106. However.96 24.2 46. (2004) found that on-farm assessments of fertilizer N use efficiency in rice fields in Asia were smaller by 25% than the average reported values determined in researcher-managed plots in farmer’s fields. For example.0 50. 8.3.2 80. the mean increases in the yield of rice. 62.7 NOCU.1 22. 2016).0 52.8 83.2 23.9.9 55. semi-medium (2-4 ha).5 53. cotton and maize by applying NCU or NOCU over urea by 6.1 43. (2010 a.4 76.3 51. 5. According to fertilizer evaluation principles.8 56.8 32.0 54. However.3 28.2 kg) followed by rice (90. 96 22. According to a report based on input survey for India for 2011-12 (Anonymous.2 21.2 and 114. cotton and maize.3. b) Will coating all urea sold in India with neem oil lead to significant increase in crop production and reduction in the demand for urea? Urea constituted 82% of the total fertilizer N consumed in India during 2015-16 (FAI. Intensity of N use is the highest in sugarcane (174. 76. Tomar and Verma. Thus it is unlikely that demand for urea will decrease in the near future due to coating it with neem oil. Vyas et al. differences in the performance of two fertilizer sources diminish at higher levels of application. farmers will never like to cut down the fertilizer dose to avoid any risk for obtaining lower yields. about 30 % arable soils have acidic reaction but very little fertilizer including urea is applied to these soils.In India. Although.5. Nitrate leaching is frequently the most important N loss process in irrigated agriculture whereas very little drainage may occur in rainfed systems. Since in terms of crop productivity. Jat and Pal. Thus. Although urea has been completely replaced with NOCU in the country. Chauhan. it is evaluated in terms of rate. Thind et al. Perhaps. 2014). 6. when NCU will be applied at lower rates as per SSNM principles or blanket recommendation. time..8% of the total urea consumed was applied to rainfed crops grown on 53. maize and cotton grown under unirrigated conditions. Further. 1990. Managing NOCU in food crops like rice. extent of yield increase due to application of NCU in place of urea as observed in different studies listed in Tables 1 to 4 is likely to result in very little impact on the overall yield increase in the country. pH and irrigation in determining the amount of NOCU to be applied in a given field. In such a scenario. Also nitrification inhibitors perform better in coarse textured soil than in fine textured ones. 3. SSNM will be able to take into account the effects of factors like soil texture. both yield benefits and reduced demand of NOCU will become visible. Also. wheat and maize following principles of site-specific nutrient management (SSNM) is possibly the only way that can lead to increased crop production and/or reduced demand for NOCU as compared to urea. wheat and maize on the basis of maintaining adequate leaf greenness as measured by leaf colour chart to individual fields will lead to application of doses of NOCU which should be less than urea and/or result in higher yield levels than those obtained with urea. As per fertilizer evaluation principles. 2016). Thus. method and place of application before it is given to farmers. benefits of coating urea with neem oil will become visible. (2010b) applied urea and NOCU to rice at 110 kg N ha-1 in a coarse textured soil and at 80 kg N ha- 1 in a fine textured soils using leaf colour chart.6% of the gross cropped area (Anonymous. hardly any agricultural university or ICAR institute has given a recommendation in terms of how much less NOCU than urea should be applied to achieve similar or higher yield levels for different crops. NOCU could produce significantly higher rice yield than urea in the coarse textured soil. In India. there is a perception that when farmers will get higher yields they will reduce the dose of NOCU as compared to urea. Respectively. 1999.3 and 4. about one-third of the total NCU being applied to rainfed crops in India is not expected to substantially increase the yield of crops. nitrification inhibitors act more efficiently in acidic soils rather than in alkaline soils in which urea is prone to be lost via ammonia volatilization and nitrification inhibitors enhance the accumulation of urea.1 % of the total amount of urea consumed was applied to rice. When a new fertilizer material is introduced. 32. the blanket recommendation for rice was 120 kg N ha-1 at both the sites. fertilizer recommendations for crops in different regions of the country are formulated as well as improved from time to time by agricultural universities and institutes of Indian Council of Agricultural Research (ICAR). Several (for example. it does not seem that demand for NOCU will be reduced as compared to urea. For example. irrigated systems show a significantly higher response than rainfed systems to the application of nitrification inhibitors (Abalos et al. 2002) have shown that per cent increase in yield of rice or wheat was conspicuously higher when comparison was made at low N levels rather than at 120 kg N ha-1 or the general recommendation for rice and wheat growing regions in India. In India.. applying N to rice. Also. in the fine textured soil both NOCU and urea were at par in increasing rice yield. Thus. as farmers adopt SSNM principles for applying NOCU to crops in individual fields. 1991. But the yield gains due to replacing of urea with NOCU are likely to be small and many times not visible. Agronomic Benefits of Neem Coated Urea – A Review 13 . In rice and wheat to which more than 50% of the urea consumed in India is applied.Neem is a key ingredient in the non-pesticidal management of different pests and provides a natural alternative to synthetic pesticides. farmers observed reduced incidence of white with the use of neem coated urea in the wheat crop. the achievable yield increase by using NOCU should be substantially less than that observed in researcher’s plots. Possibly. In about 30% comparisons. Nitrification inhibitors work better in acidic soils than in neutral or alkaline soils. sporadic incidences cannot make a case in favour of neem coated urea materials. At Panipat in Haryana. As farmers increasingly adopt SSNM principles for fertilizer management. Baboo (2014) has cited a few case studies associated with neem coated urea. At one of the locations in the state of Uttar Pradesh. Conclusions Urea coated with neem cake (200 kg t-1) (NCU) or neem oil (0. Thus. Agronomic Benefits of Neem Coated Urea – A Review 14 .5 kg t-1) (NOCU) possesses nitrification inhibition properties and can increase yield and N use efficiency in field crops more than untreated urea. Positive impact of NOCU in increasing crop production is likely to be further lowered by the fact that effect of nitrification inhibitors depends also upon the soil texture. Until and unless pesticidal or repellent effects of neem coated urea are documented through well planned studies. mean increase in grain yield by replacing urea with NCU or NOCU is 5 to 6% in plots managed by researchers. untreated urea should be expected. although quality of neem oil and neem cake in terms of concentration of triterpenoids can vary in different lots. no increase was observed. farmers observed that the menace of blue bull (Boselaphus tragocamelus). More than 30% of total urea consumed in India is applied to crops grown under rainfed conditions. Till new recommendations for using NOCU are formulated for different crops and regions. farmers observed no incidence of leaf folder and stem borer in the rice crop. and in irrigated crops than in rainfed crops. in coarse textured soils than in fine textured soils. demand for NOCU may contract from the present level of demand for urea. pH and whether the crops are irrigated or rainfed. Farmers applying high and above optimal levels of urea-N in different crops may not observe significant improvement in yield levels by applying NOCU. no reduction in demand for NOCU vs. and at Sangrur and Gurdaspur in the state of Punjab. applying NOCU following the SSNM principles will lead to crop production of higher or similar levels as observed with untreated urea but with lower fertilizer application rates. the largest Asian antelope and endemic to the Indian subcontinent. 2000). on an overall basis. replacing all urea being supplied to farmers in the country with NOCU is not likely to show a significant impact on food production levels. was substantially reduced in rice fields where neem coated urea was applied. hardly any systematic attempt has been made to study pesticidal properties associated with NCU or NOCU. As level of crop management and plant protection in farmers’ field is generally lower than in the researcher’s plots. 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