The flows of reactive N in terrestrial, aquatic and atmospheric ecosystems in India are being increasingly regulated by inputs, use efficiency and leakages of reactive N from agriculture. In the last three decades, use of reactive N in the form of chemical fertilizers has kept pace with the production of foodgrains, although the consumption is concentrated in certain areas with intensive farming. As for cereal-based agriculture, recovery of N by rice and wheat at on-farm locations in India rarely exceeds the 50% mark. Agricultural activities in India account for more than 80% of the total N sub(2)O emissions, including 60% from the use of N fertilizers and 12% from burning of agricultural residues. In Asia, reactive N transfers to the atmosphere by NH sub(3) volatilization are expected to reach 19 Tg N yr super(-1) in the next three decades; 29% being India's contribution. Of the total anthropogenic emissions of NO sub(X) and N sub(2)O from Asian agriculture, about 68% is due to the combined contributions of India and China. Additionally, riverine discharge of dissolved inorganic N derived from N in river basins and leaching of nitrate-N to the surface and ground water bodies also contributes to the application of reactive N in agriculture. Integrated management of organic amendments and fertilizer N can improve efficiency of reactive N use by crop plants, while achieving targets of productivity and quality. The greatest challenge in improving N use efficiency lies in developing precision management of reactive N in time and space. Approaches to maximize synchrony between crop-N demand and the supply of mineral N from soil resources along with reactive N inputs in high-yielding agricultural systems are critical towards this end. Among a host of upcoming technologies aimed at improving N management strategies, leaf colour charts, chlorophyll meters and optical sensors, which allow in-season estimation of N requirement of crops, are the most promising.
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机译：印度陆地，水生和大气生态系统中反应性氮的流量正日益受到投入，使用效率和农业中反应性氮泄漏的调节。在过去的三十年中，尽管化肥的消费集中在某些集约化耕作的地区，但化学肥料形式的反应性氮的使用却与之保持同步。至于谷物农业，印度农场上稻米和小麦的氮素回收率很少超过50％。印度的农业活动占N sub（2）O排放总量的80％以上，其中60％来自使用氮肥，而12％来自燃烧农业残留物。在亚洲，通过NH sub（3）挥发，反应性N转移到大气中，预计在未来的三十年中将达到19 Tg N yr super（-1）。印度贡献了29％。亚洲农业在人为排放的NO sub（X）和N sub（2）O排放总量中，约68％是印度和中国的共同贡献。另外，河流中氮源的溶解性无机氮在河流中的排放以及硝酸盐氮向地表水和地下水体的淋溶也有助于活性氮在农业中的应用。对有机改良剂和肥料氮的综合管理可以提高农作物对活性氮的利用效率，同时实现生产力和质量目标。提高氮利用效率的最大挑战在于发展对反应性氮的时空精确管理。为此目的，使作物氮需求与土壤资源矿质氮供应以及高产农业系统中活性氮输入之间的同步最大化的方法至关重要。在旨在改善氮素管理策略的一系列即将到来的技术中，叶色图表，叶绿素计和光学传感器可以对作物的氮素需求进行季节估算，这是最有前途的。
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