Development of nitrogen fertilizer recommendations for arable crops in the Netherlands in relation to nitrate leaching

In the Netherlands, current nitrogen fertilizer recommendations for arable crops are based on the amount of soil mineral nitrogen in early spring. The larger the amount of soil mineral nitrogen, the lower the recommended application rate of fertilizer nitrogen. A more refined method is to draw up a balance sheet in which the nitrogen requirement of the crop is given on the one side and the contributions of fertilizer nitrogen, soil mineral nitrogen, and the amount of nitrogen mineralized during the growing period on the other. The most refined method of nitrogen fertilizer recommendation is the use of a simulation model that predicts the daily crop nitrogen requirement and nitrogen supply to the crop from various pools during the growing period. A simulation model thus adds the time element to nitrogen fertilizer recommendations. Moreover, in contrast with the other two methods, a simulation model allows identification of environmental side-effects of nitrogen fertilizer application.The current Dutch nitrogen fertilizer recommendations aim at predicting the economically optimum application rate of fertilizer nitrogen. From the environmental point of view it is interesting to know how much soil mineral nitrogen has accumulated in the soil at harvest, because this nitrogen is a potential loss to the environment through nitrate leaching during the subsequent winter period. If the economically optimum application rate of fertilizer nitrogen is applied to arable crops, it is unlikely that soil mineral nitrogen accumulates, except in the case of potatoes. Model calculations have shown that accumulation of soil mineral nitrogen after potatoes can be prevented when the recommended nitrogen application rate is reduced by 25%. In that case tuber yield is reduced by only 2%.     

Reaction products of triammonium pyrophosphate in different Indian soils

Studies were undertaken on the isolation and identification of reaction products of triammonium pyrophosphate (TPP), the major non-orthophosphate constituent of ammonium polyphosphate newly introduced in India, in representative soils of the alfisol, oxisol, entisol, mollisol and vertisol groups of India. Saturated solution of TPP were reacted with soils for periods of 30 minutes and one day with corresponding precipitation times of 15 days, three months and one year to isolate reaction products which were identified by X-ray diffraction technique, infra-red spectroscopy and chemical analyses. Six reaction products, namely, Ca(NH₄)₂P₂O₇ · H₂O, Mg(NH₄)₂P₂O₇ · 4H₂O, Ca(NH₄)₄H₂(P₂O₇)₂, Ca₃(NH₄)₄H₆(P₂O₇)₄·3H₂O, FeNH₄P₂O₇ and NH₄Al_0·33 Fe_0·67P₂O₇ were identified in different soils; Ca(NH₄)₂P₂O₇·H₂O and Mg(NH₄)₂P₂O₇ · 4H₂O occurring in abundance in most soils. Significant hydrolytic degradation of pyrophosphate reaction products to orthophosphate was not observed.Complementary studies where TPP in solid form was applied to soil, and reaction formed at and around the site of TPP placement were identified after six weeks incubation also showed the formation of Ca(NH₄)₂P₂O₇ · H₂O and Mg(NH₄)₂P₂O₇ · 4H₂O in the soils examined.     

Slow-release urea fertilizers — effect on floodwater chemistry,ammonia volatilization and rice growth in an alkali soil

In experiments with transplanted rice (Oryza sativa L.) at the Central Soil Salinity Research Institute, Karnal, India, two methods of application of granular urea, wholly as basal dose U(W) or in splits U(S) were compared with deep, point placement (8 cm) of urea supergranules and broadcast application of two slow-release sources, sulphur-coated urea (SCU) and lac-coated urea (LCU). Comparisons were made in wet season 1984 and 1985 on the basis of ammoniacal N concentration and pH of floodwater, ammonia volatilization, rice yield and N uptake.In 1984 the highest peak concentrations of ammoniacal N (AN) in the floodwater, > 12g m^–3, and ammonia volatilization losses 54% of applied N were produced in U(W). Application of N in splits U(S) reduced peak AN levels 5g m^–3 and losses to 45.1%. LCU was ineffective in reducing peak AN levels ( 7.5g m^–3) or losses (43.6%). However SCU and USG were effective in reducing peak AN levels to < 2g m^–3 and N losses to 16.9 and 3.4% respectively. Total ammonia volatilization losses as well as the initial rate of loss correlated very well with the peak levels (second day) of AN, NH₃ (aq.) as well as equilibrium vapour pressure of NH₃. Floodwater pH was between 9.5 and 10.0.Split application of granular urea was generally more efficient in terms of yield and N recovery (41.4%, average of two years) as compared to whole application (29.5%). LCU was ineffective in improving grain yields or N recovery (30.9%). SCU was ineffective in improving grain yields but improved N recovery to 57.9%., USG increased grain yields only in first year by 19% over U(S) and improved N uptake to 60.5%. A negative linear relationship was established between N uptake by rice at harvest and AN levels in floodwater two days after fertilization which can be used as an index to evaluate fertilizers.     

Addition of gel-forming hydrophilic polymers to nitrogen fertilizer solutions

Environmental and economic concerns are causing a search for more effective fertilizer products and improved methods for managing existing fertilizers. This laboratory and greenhouse study was conducted to determine if the addition of gel-forming, hydrophilic polymers to N fertilizer solutions could reduce N leaching loss and increase plant uptake of N. In the first experiment, a solution of urea ammonium nitrate (UAN, 32% N) was mixed with a variety of polymers at three concentrations, band applied to a sandy soil, and leached weekly for six weeks. Nitrogen leaching losses were reduced from 0 to 45% during the first four weeks due to polymer addition, compared with UAN alone. A second experiment examined the addition of various guar (Cyamopsis psoralides DC.)-derived polymers to UAN as a means of reducing N loss and increasing plant growth. Leaching losses were reduced an average of 26, 16, 7, and 7% for the first four weeks following fertilizer application with the addition of polymer. When UAN was applied with some polymers, growth of fescue (Festuca arundinacea L.) was increased as much as 40% and N accumulation increased as much as 50% as contrasted with UAN alone. These experiments indicate that under highly leached conditions, N leaching loss may be temporarily reduced and plant recovery of N increased through use of some gel-forming, hydrophilic polymers.     

日光温室CO2自动施肥系统的研制

研制了具有自动化特征的CO2施肥系统及其技术，并对该项技术的施肥效果进行了试验。结果表明：利用此装置，日光温室内的CO2浓度均匀程序较好，经济上可行，且气源来源广泛，长期施用对大气和土壤无污染，该项施肥技术加速了中国温室生产技术与世界发达国家接轨的进程。     

我国有机肥料产业化利用现状及发展前景

概述性地介绍了我国有机肥料资源数量和分布,有机肥料产业化发展现状,包括有机肥料产业化模式、生产规模、生产能力等;同时综合分析了我国有机肥料产业化发展中存在的问题和发展前景。     

中氮氨合成系统的技术改造

通过分析氨合成系统技术的发展趋势。指出了中氮厂氨合成系统技术改造的方向。总结了中氮厂氨合成系统技术改造的主要内容和主要的改造技术。     

电磁场对半连续铸造铝合金晶粒组织的影响

以天然高分子化合物溶液为粘结剂,添加无机矿物材料制成涂膜材料;用该涂膜材料包裹尿素制成了缓释肥料。通过土柱淋洗试验对该缓释肥料的养分释放特性进行评价,结果表明有机无机涂膜材料包裹尿素类化学肥料,制成的包膜肥料具有良好的缓释性能,且这种缓释性能与涂膜材料中有机高分子化合物的浓度有关;随着有机化合物浓度增加,肥料的有效成分释放速度变缓,且最大释放速率出现时间后移、峰值变小,表现出了较好的可控制性。     

谈谈加强化肥产品质量监督的看法

本文对化肥产品在生产、销售环节中,如何加强质量监督和市场监督提出切实可行的建议。     

化肥企业CO_2回收项目可行性分析

江苏恒盛化肥有限公司拟以化肥生产装置产生的尾气为原料,采用吸附精馏法工艺技术,投资建设30万t/a CO2回收项目。从项目概况、工艺技术路线、工艺流程、产品市场等方面分析了项目建设的可行性。结果表明,该项目具有CO2气源稳定、生产技术先进、市场销售前景看好的优势。