Mitigating temperature stress by timely planting of wheat
Wheat is an important cereal crop and staple food in Pakistan. Most of the wheat is cultivated late after cotton, rice and sugarcane. Introduction of long duration Bt cotton varieties further pushed its sowing to late December or even early January. Late sowing of wheat crop results in yield loss in the Punjab province. A study has been conducted in experimental fields of Wheat Research Institute, AARI, Faisalabad, Pakistan to find out the possible reasons of low grain yields in late sown crop. Twelve experimental wheat lines were planted on seven sowing dates starting from 1st November to 30th December with ten days interval. The experimental design was a factorial combination of seven sowing dates as main plots and twelve varieties/ genotypes as subplots in a split-plot design with three replications. Effect of temperature on several crop growth stages was studied. Mean minimum temperature during the month of December, 2016 and January, 2017 remained below 5?C and mean maximum was more than 30?C during March 2017. Weather conditions experienced by the crop at each developmental stage were compared with the optimum conditions required on that specific stage in each sowing date. It was revealed that in late sown crop, different phonological/growth stages of the crop and yield components and grain yield were affected negatively. It was concluded from the study that the late sown crop suffered from two types of temperature stresses. The late sown crop faced low temperature stress at starting phase which result in delayed germination and low tillering. At caryopsis formation and grain filling the same crop face high temperature stress causing reduced grain formation and shriveled grains due to enforced maturity. Sowing of wheat at proper time i.e., by the end of November was recommended to fetch maximum yields.