Canopy temperature depression and normalized difference vegetation index as indicators of drought resistance and nitrogen recommendation in hybrid maize genotypes

Accepted: 25 June 2020 Improving maize production is one of the most effective strategies for solving a food insecurity issue. Differences in the normalized difference vegetation index (NDVI), canopy temperature depression (CTD), and grain yield were evaluated for 14 hybrid maize genotypes at Sundarbazar, Lamjung, Nepal. During a growing season (May to September, 2019), the NDVI was measured using a Greenseeker handheld sensor to predict in-season yield and nitrogen (N) recommendations. The CTD was measured using a Fluke infrared thermometer to estimate yield and determine heat resistant genotypes. Both NDVI and CTD showed significant positive relationships with grain yield. For the NDVI, the coefficient of determination (R) were 0.66, 0.52, 0.76, and 0.49 at 15, 30, 45, and 60 days after sowing (DAS), respectively. For the CTD, R values were 0.41, 0.45, 0.59, and 0.58 at 15, 30, 45, and 60 DAS, respectively. Nitrogen (N) requirement from the NDVI-based N calculator for the yield potential under the farmers’ nutrient management levels, regardless of genotypes, was nearly half of the recommended N dosages. The genotypes with negative CTD values (RML-11-2/ RML18, RL-35-1/RL-105, and RL-24-0/RL-111) were particularly prone to heat stress, while all other genotypes were heat stress-resistant. The results indicated that top dressing of ~54kg N ha is required at 45 DAS. Nitrogen requirements decreased as crop growth progressed towards the reproductive stage. Results indicated that 45 DAS was an appropriate time for the top dressing of N, and the application of N at a later stage of crop growth had a smaller advantage.