Precision nitrogen management improves grain yield, nitrogen use efficiency and reduces nitrous oxide emission from soil in spring maize

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 (R-2= 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.