Fertilizer Research 13:181 189 (1987) © Martinus Nijhoff Publishers, Dordrecht-- Printed in the Netherlands
181
Status of fertilizer products under development in India H.L.S, T A N D O N Fertilizer Development and Consultation Organization C 110, Greater Kailash L New Delhi 1100048, India
Accepted 19 March 1987 Key words: new fertilizers, fertilizer efficiency,India, nitrogen fertilizers, phosphatic fertilizers Abstract. This paper describes the status of various fertilizer materials in the process of
development and testing. These include a range of products such as urea supergranules, urea coated with an array of coating agents, nitrogen solution, partially acidulated phosphate rocks, potyphosphates, compost-enriched or cattle-dung incubated rock phosphates, and single superphosphates fortified with boron or zinc. To the extent possible, economic aspects and future needs are also commented upon.
Introduction
Fertilizers occupy a very i m p o r t a n t position in Indian agriculture. Significant developments have taken place during the past 25 years both in the p r o d u c t i o n and c o n s u m p t i o n o f fertilizers. The c o n s u m p t i o n o f fertilizer nutrients crossed the one million tonne mark in 1966-67. During 1986-87, the c o n s u m p t i o n o f N + P205 + K20 is expected to reach 9 million tonnes. Fertilizers are estimated to be responsible for 60 million tonnes or 40% o f the total foodgrain o u t p u t [29]. While a n u m b e r o f fertilizers are available to farmers, 4 materials account for 80% o f the fertilizer tonnage distributed. These are urea, d i a m m o n i u m phosphate, single superphosphate and potassium chloride (Table 1). Alongside the above-mentioned fertilizers, there is a certain a m o u n t of research and development activity to develop and test new materials. These are aimed either to improve nutrient use efficiency or to make a more productive use o f locally available resources. This paper provides an account o f the present status o f fertilizer materials under development in India. Materials containing nitrogen, phosphorus, zinc and b o r o n form the present scenario and are discussed,
182 Table 1. Share of different fertilizers in the nutrient distribution in India, 1985-86.
Fertilizer
Urea Ammonium Sulphate Calcium Ammonium Nitrate Single Superphosphate Potassium Chloride Diammonium Phosphate Urea Ammonium Phosphate 28-28-0 Ammonium Phosphate Sulphate 20-20 Nitrophosphate 20-20-0 NPK 12-32-16 NPK 17-17-17 NPK 10-26-26 NPK 19-19-19 NPK 15-15-15 Total nutrient in million tonnes
Percent share N
P
K
79.9 1.8 1.9 7.2 1.6 1.6 0.9 1.2 1.6 0.5 0.6 0.7
16.4 51.3 3.9 4.4 2.4 9.2 4.4 3.7 1.7 1.9
60.8 11.0 10.5 8.8 3.9 4.6
5.66
2.03
0.85
Source: FAI Annual Review of Fertilizer Production and Consumption 1985-86.
Urea Supergranules(USG) These are typically 1-g spherical granules o f urea which have been p r o d u c e d primarily to facilitate point placement o f N in flooded rice soils for higher N-use efficiency. Material for testing is presumably p r o d u c e d by briquetting o f urea prills. A fair a m o u n t o f field data on the performance o f U S G have been generated, b o t h in " o n - s t a t i o n " and in " o n - f a r m " trials. Barring light-textured, highly permeable soils, deep placed U S G s are associated with a m e a n yield advantage o f 400-600 kg p a d d y rice/ha over prilled urea at application rates o f 8 0 - 1 0 0 k g / h a [12, 15, 25, 26]. In very light soils, the U S G s have not been f o u n d suitable, mainly due to the leaching o f unhydrolysed urea-N [10]. It is reported that the U S G could be m a d e commercially available at 10% extra cost over prilled urea [12]. Point placement o f U S G , being a labourintensive practice, m a y require 8-10 m a n d a y s o f h u m a n labour. Table 2 shows that if U S G cost 10% m o r e and labour wages are R s l 5 / d a y , then a yield advantage o f a b o u t 135kg p a d d y is needed to offset the additional costs. If the m e a n yield gain is taken at 500 kg paddy/ha, then the U S G technology appears to be economically attractive. The U S G s have not gone into commercial p r o d u c t i o n as yet but the setting up o f some capacity is expected. One o f the constraints in the wider
183 Table 2. A m o u n t of paddy rice required to pay for extra costs associated with the use of urea supergranules at an assumed rate of 100kg N / h a and labour requirement of 10 person days/ha. Extra cost of U S G as % over prilled urea
5 I0 15
kg paddy rice required to offset extra cost of material plus labour Labour Rs 10/day
Labour Rs 15/day
Labour Rs 20/day
84 100 118
118 134 151
151 167 185
adoption of U S G is the lack of simple, inexpensive and light weight applicators on a large scale. A number of applicators are at various stages of testing. Some data would also be needed on the extent of granule breakage during loading/unloading and handling stages and how this can be reduced. Some of these aspects have been discussed in detail elsewhere [37].
Neem-coated/blended Urea (NCU) Interest in this material arose largely from a 1971 report that the seeds of neem (Azadirachta indica) may have nitrification-inhibiting properties [1]. The neem tree grows widely in India in a natural state. A mean yield advantage of 400-500 kg paddy rice/ha has been reported with neem-coated urea over prilled urea [26] though the results are not consistent. Part of the field variability could be due to differences in water management practices and rather unstandardized procedures for treating urea with neem seed cake. The treatment varies from physical mixing to fine blending to coating urea prills with neem seed cake making use of a suitable sticker. When coal-tar is used as a sticker, part of the efficiency advantage is seen to be due to the tar coating itself [13, 36]. Neem-treated urea has been shown to be superior over prilled urea particularly under poor water management conditions in the field [31]. Potential availability of neem cake is estimated at 330 thousand tonnes if all the 400 thousand tonnes of the seed which are shed annually are collected and crushed [7]. This is naturally a theoretical figure because neem trees are scattered all over the landscape, and there are no organized plantations, incentives or facilities for their collection. For blending purposes 200 kg neerncake would be needed per tonne of urea. When coated with a sticker, the requirement of neem cake would be lower. The extra cost per unit N from neem coated/blended urea may range from 8 to 33% over prilled urea (Table 3). It is clear that lab-scale cost estimates
184 Table 3.
Some estimates of additional costs associated with modifiedurea fertilizers [37].
Material
Increase in cost over prilled urea (%)
Urea mixed with neem cake Urea coated with neem cake Urea blended with neem cake Urea supergranules Rock-phosphate coated urea Gypsum-coatedurea
8 (simple mixing) 11 (lab-scale cost) 33 (commercial) 20-25 (includes extra labour) 10-15 10-15
are lower than when the technique is commercialized. Though the neemurea products hold promise and are in fact recommended in some states, no data are available about the quantities treated or distributed. The technology appears to hold promise, especially in the form of small-scale enterprises in the rural areas where sufficient neem trees are available and the product can find use with a minimum of handling and transportation costs. Quality standards will obviously have to be estblished to safeguard the interest of the farmers. Ureas coated with other cakes and materials have also been tried, though on a much smaller scale than neem-treated materials, some of these are karanj or Pongamia glabra [33], Shorea robusta [21] and Citrullus colosynthis [9].
Urea Ammonium Nitrate Solution A urea ammonium nitrate solution (32% N) has been formulated and tested for a number of crops [24]. In general, it is agronomically on par with solid N-carriers under upland conditions. Aspects concerning its transport, distribution, application and quality control are probably more important at this stage than the simple agronomic performance. It has been reported that mild steel tankers of 10 tonne capacity with a metering device could satisfactorily transport the solution from the factory so that farmers can collect the quantities needed in jerrycans or drums [5]. Latest cost estimates relative to solid N-fertilizers in the market such as urea and CAN are not available, although 1983 estimates indicated the production cost of this material as 60% of that for prilled urea [24].
Urea-gypsum Products have been developed both by coating of urea with gypsum and by melt granulation. In one case urea is coated with gypsum using water as the
185 binder [32]. Yield advantages from urea-gypsum as compared to untreated N-carriers such as urea or AS were generally similar for rice, significantly more for tobacco but less for sugarcane. Urea-gypsum products developed by melt granulation have also been tested. In one case the end product was made by solidifying urea melt on a moving bed of gypsum [32]. In another case, granular products were prepared in a paddle-type, hand-operated granulator and with 20% phosphogypsum content products of good granular quality containing 37% N were obtained [19]. In tests under controlled conditions, ammonia volatilization losses from urea-gypsum were lower than from pilled urea [19]. field results with this material are yet to be reported.
Urea formaldehydes There is a renewed interest in slow-release fertilizers based on urea formaldehyde, particularly for plantation crops grown on light-textured soils in high rainfall areas. In addition to ureaform, ureaform-based NP formulations in 10 g size tablets and N P K formulations (10:4:20) which contain ureaform, supe,rphosphate and potassium chloride/potassium sulphate have been developed at the R & D center of FACT Ltd. These materials appear promising, particularly for increasing N-efficiency in coconut plantations on sandy soils where up to 80% of the N applied through conventional sources could be lost. Various aspects of these products were discussed at a workshop organized at the Central Plantation Crops Research Institute in November 1986 and a number of crops were identified for future research.
Lac-coated Urea (LCU) Products coated with shellac have been developed and tested on a moderate scale. The LCU contains 33% urea-N, and the final product carries 18% rosin ester of lac, 3.3% double-boiled linseed oil, 3.6% paraffin wax, 2.9% soap, and 0.2% bitumin (34). It is expected that some new line of sulphur-coated ureas and plasticcoated ureas will also be tested under Indian conditions using imported materials.
Rock-phosphate-coated Urea Products containing 36% N and 5% P205 have been developed and tested. The material contains 80% urea, 15% rock phosphate and 5% oil having a
186 dissolution rate of 5% in one day, 25-30% in 7 days and all in 25-30 days [32]. It produced rice yields comparable with those achieved with the best split application of N; however, there was considerable inter-site variability. Rock P-coated urea is estimated to cost 10-15% more than prilled urea (Table 3).
Coal Acids Some information on fertilizers derived from coal has been reported [14]. The 2 coal acids are Ammonium polycarboxylate or AMP (total N 14%, available N 9%) and Composite ammonium polycarboxylate or CAMP (total N 16%, available N 14%). Nitrohumic acid also seems to be promising, for blending with conventional N-fertilizers. This is an intermediate of coal acid production. Optimum blending proportion for high efficiency is given as 15-20% HNA by weight of urea and 10% for treating ammonium sulphate. Benefit: cost ratios of 12:1 to 25:1 have been reported with these materials [14]. At such attractive benefit: cost ratios, it is not clear why these materials have not found practical-scale application or what the constraints are in taking them from the lab to the land.
Partially Acidulated Phosphate Rock (PAPR) The first papers on PAPR appeared almost 18 years ago in India [23], but it is only now that a demonstration-scale plant for the production of PAPRs is being set up [8]. Some recent agronomic results have been summarized [8]. These suggest that PAPR with 50% acidulation is as good as 100% watersoluble P in neutral-alkaline soils and that 25% acidulated material is only slightly inferior to water-soluble P. These observations are different from the mass of available data on the optimum water solubility for neutral-alkaline soils in India [38]. The PAPR pilot plant is expected to provide materials with 25 and 50% acidulation using both sulphuric acid and phosphoric acid. In a recent rview, 10-20% acidulation has been suggested for upland crops and soils of pH around 5.5 having high P-fixation capacity while 50% acidulation has been proposed for soils of low P-fixing capacity [16]. Actual potential of the PAPRs will depend upon the performance of the products made available by the demonstration plant for field-scale trials.
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Materials incubated with organic materials Efficiency of insoluble P or citrate-soluble P has been shown to increase when pre-incubated with fresh cattle dung prior to application to the soil. In 15 weeks of incubation, 5.8g citrate-soluble P was transformed into water-soluble P by 1 kg dung on dry weight basis [11]. Availability coefficient ratios of citrate-soluble P in comparison with DAP improved upon incubation. Performance of this material under farmers' conditions and its handling and storage aspects have yet to be worked out. Composts enriched with rock phosphate or 'Zphospho-composts", as these are called, have been reported to result in higher crop yeilds and better P-use effÉciency [3, 17, 18]. Researchers have concluded that low-grade phosphate rocks can be utilized efficiently by preparing phospho-composts [18]. Work has also been reported with SSP blended with cow-dung, biogas slurry or mixed with silicates, which shows that these techniques help in improving the efficiency of applied P [6]. Again, large-scale testing, economics and field-scale aspects have yet to be studied.
Polyphosphates Available results show that there is a scope for the use of poly-phosphates in Indian agriclutrue [2, 3, 39]. These materials were found suitable for rice, maize, wheat and sorghum. In the alkaline soils of Punjab state, tetraammonium pyrophosphate was less efficient than the common ortho forms for maize in terms of dry matter production, Pdff and % utilisation of fertilizer P, but furnished higher values of available P after harvest than MAP or DAP [4]. A pilot plant for the production of granulated polyphosphates has been set up with 20 kg/hr capacity [22]. The product is reported to have 12-15% N, 55-57% P205 and less than 1% moisture.
Liquid NP Fertilizer There is small-scale activity in the development of liquid calcium nitrophosphate fertilizer (444)). A small N-arc reactor is used to produce nitric acid which acidulates low-grade phosphate rock and is visualized as an on-farm fertilizer factory [28].
188 Zincated single superphosphate Ordinary superphosphate fortified with zinc sulphate to carry 2.5 % zinc has been developed and tested [27]. The interest in zincated-SSP is largely in response to the widespread deficiencies of both P and Zn in Indian soils. Available field data show that the mean yield of wheat from 10 trials with zincated SSP was 106 (range 87-132) as compared to 100 in plots receiving SSP and zinc sulphate separately. The product is considered suitable for field use [35].
Boronated single superphosphate Fertilizer SSP fortified with borax carries 0.18% B in addition to 16% P205. Field results with a number of crops have been summarized [30]. This material is commercially available in the western states, particularly for the groundnut crop. Boronated SSP costs the farmer Rs 130 (US$10) per t o n n e extra over ordinary SSP.
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