Canopy temperature as indicator of thermal and nutrient stresses in wheat crop

The field study was conducted at research farm, School of Climate Change and Agricultural Meteorology, Punjab Agricultural University, Ludhiana during rabi 2013-14 and 2014-15 to find out effect of different thermal regimes, nitrogen levels and post anthesis strategies on the canopy temperature and its indices for the wheat crop. The treatments comprised of three temperature regimes in main plot (D-1 - October 30, D-2 - November 15 and D-3 - November 30), three nitrogen levels in sub-plot (N-1 - RDF- Recommended dose of N, N-2 - 125% RDF (25% more than recommended N), N-3-150% RDF (50% more than recommended N) and four stress management post-anthesis strategies (P-0 - Control-No Spray, P-1 - Water sprayed, P-2 - Foliar spray of ZnSO4 center dot 7H(2)O @ 0.5% P-3- Foliar spray of Thiourea @ 10 inM) at anthesis and 20 days after anthesis in sub-sub plot as split-split plot design replicated thrice. Canopy temperature was recorded at different phenological stages. The stress degree days were calculated at maturity. The results showed that crop sown on October 30 experienced lower canopy temperature at later stages as compared to November 15 and November 30 sown crop. With increase in nitrogen application it also lowers down the canopy temperature by 1.0 to 2.0 degrees C as dense and good crop stand under 150% RDF than others. The spray of crop with water, ZnSO4 center dot 7H(2)O and Thiourea also helped to bring the canopy temperature low at anthesis or after that when sprayed at regular intervals because these chemicals helped the crop to avoid the heat stress during this period by lowering the canopy temperature 0.5 to 1.0 degrees C. Higher the negative SDD values under October 30 as compared to November 15 and November 30 reflect that canopy temperature is cooler which means that crop is healthy and without any stress. Increase in N dose has lowered the SDD, indicating a better canopy thermal environment under higher N application. The significantly linear and negative relationship has obtained with canopy temperature and grain yield as well as SDD and grain yield.