Precision nitrogen (N) management sustains high grain yield with low N optimum dose and thus may help reduce the escape of reactive nitrogen from soils to the atmosphere. Two-year field studies were conducted at two locations in sub-tropical and sub-humid climate in Indo-Gangetic plains of South Asia with the objectives to establish precision N management technology for fertilizer N topdressings in spring maize while quantifying nitrous oxide emission from soil. A significant positive correlation of 0.64 to 0.90 between LCC (Leaf color chart) scores and leaf N concentrations at different growth stages indicated that LCC scores can successfully be used as an index of leaf N content for precision N management in spring maize. A close linear relationship (R² = 0.75) between chlorophyll meter (SPAD) readings and LCC score showed that like SPAD meter, LCC score can reliably consider leaf greenness as an indicator of leaf N concentration. Cate-Nelson plot of LCC scores verses relative grain yield expressed LCC score 5 as the threshold for sustaining potential yield. Fertilizer N topdressings based on threshold leaf greenness of LCC 5 produced 6 to 10 percent higher grain yield with improved recovery and agronomic efficiencies in comparison to soil-test based N recommendations. Nitrous oxide emission estimated using Cool Farm Tool (CFT); an empirical model specified that application of 120 kg N ha⁻¹ at LCC 5 down turned nitrous oxide emission by 8.0 percent compared to soil test-based N management.

精确的氮（N）管理以低的N最佳剂量维持高谷物产量，因此可以帮助减少反应性氮从土壤到大气的逸出。在南亚印度恒河平原的亚热带和亚湿润气候的两个地方进行了为期两年的田间研究，目的是建立用于春季玉米肥料氮追肥的精确氮管理技术，同时量化土壤中一氧化二氮的排放。LCC（叶色图）得分与不同生育阶段的叶片N浓度之间存在0.64至0.90的显着正相关，表明LCC得分可以成功用作春季玉米精确氮管理的叶片N含量指标。紧密的线性关系（R ²叶绿素计（SPAD）读数与LCC分数之间的差值= 0.75）表明，与SPAD计一样，LCC分数可以可靠地将叶片的绿色作为叶片氮含量的指标。LCC得分的Cate-Nelson图相对于相对谷物产量表示LCC得分5为维持潜在产量的阈值。与基于土壤试验的氮素推荐相比，基于LCC 5阈值叶片绿色度的氮肥追施可提高6％至10％的谷物产量，并具有更高的恢复率和农艺效率。使用Cool Farm Tool（CFT）估算的一氧化二氮排放量；一个经验模型规定，与基于土壤试验的氮管理相比，在LCC 5处施用120 kg N ha ^-1可使一氧化二氮排放降低8.0％。