Nitrogen application based on decision support tools to enhance productivity, nutrient-use efficiency and quality of sweet corn (Zea mays)

A field experiment was conducted during the winter (rabi) seasons of 2014 and 2015 at Raichur, Karnataka, to establish optimum thresholds of leaf colour chart (LCC), chlorophyll meter (SPAD) and normalized differential veg-etation index (NDVI) to guide in-season crop need-based N fertilizer application. Treatment consisted of LCC thresholds 4 and 5, SPAD 40 and 50, NDVI thresholds 0.6 and 0.8 with 30 kg/ha N whenever N level fell below threshold, blanket N (150 kg N/ha) either 2 or 3 splits, half recommended dose of nitrogen (RDN) basal + half to foliage as 2% urea at 30, 45 and 60 days after planting (DAP), and control (without N). Results revealed that LCC 5, SPAD 50 and NDVI 0.8 corresponding to 120 kg N/ha recorded higher sweet corn yield with or without husk cob, fresh grain quality and nutrient uptake over blanket 150 kg N/ha at fixed intervals. These decision support tools based N management helped to save N fertilizer 20 to 40 kg/ha besides improving agronomic efficiency of N.