Optimization of nitrogenous fertilizers using leaf-colour chart for irrigated hybrid maize (Zea mays) grown in Vertisol of sub-tropical India

A field experiment was conducted at Raichur, Karnataka, India, during the rainy seasons of 2016 and 2017, to study the response of hybrid maize leaf-colour chart (LCC) to N and evaluate threshold to enhance crop yields, Nuse efficiency (NUE) by altering splits as per crop need guided by LCC. Treatments included LCC thresholds of 1, 2, 3, 3.5, 4, 4.5, 5 and 6 compared with fixed splits at definite growth stages and absolute control. Application of 30 kg N/ha, whenever greenness of first fully opened leaf from the top was less than shade of the thresholds on the LCC. Hybrid maize showed significant response to application of N up to 120 kg N/ha in 3 equal split doses. Beyond this level, fertilizer NUE was significantly reduced. The LCC < 5 proved better than other LCC shades for guiding real-time N management and achieving higher NUE. Application of 80-110 kg N/ha using threshold LCC < 4.5 inclusive of 62.5 kg N/ha basal resulted in higher grain yield of maize which was at par with the application of 150 kg N/ha applied in 3 equal split doses.