Quantification of microclimate of cotton hybrids under different sowing environments

An experiment was conducted to quantification of microclimate of cotton hybrids under different sowing environments at research farm of Department of Agricultural Meteorology, Chaudhary Charan Singh Haryana Agricultural University, Hisar (long.750 46 / E, lat. 29010 / N and alti. 215.2 meters MSL) during kharif season of the year 2013. The main plot treatments consist of three date of sowing i.e. D1- 4th week of April, D2- 2nd week of May, D3- 4th week of May and sub plot treatments consist of two Bt hybrid i.e. V1- Ankur 3028 BG II, V2- BIO 6588 BG II and non Bt hybrid V3- HHH 223 with two row orientations i.e. NS- North-South and EW- East-West. The eighteen treatment combinations were tested in split plot design with three replications. Dry and wet bulb temperatures were measured at a interval of three hours from morning to evening at the three levels of crop canopy i.e. lower, middle and upper with the help of Assmann Psychrometer at different phenophases of cotton. These values were used to find out the microclimate parameters i.e. temperature, relative humidity and vapour pressure with the help of psychrometric tables. Diurnal temperature and relative humidity profiles at different growth stages of different cotton under three sowing environments with two row orientations i.e. NS- North-South and EW- East-West were studied. The morning and evening time temperature profiles were inverse and lapse i.e. increase and decrease in temperature with height inside the crop canopy respectively, whereas, noon hours profiles were nearly isothermal. Diurnal temperatures were higher in east-west cotton hybrids as compared to north-south hybrids. The diurnal spread of temperature profiles was higher in first sown cotton hybrids as compared to late sown hybrids. The diurnal spread of temperature profiles was nearly same in all the cotton hybrids. The relative humidity profiles were lapse i.e. decrease in humidity with crop height in all the treatments under north-south and east-west conditions. The relative humidity was higher in north-south crop as compared to east-west hybrids. The diurnal spread of relative humidity profiles was less in case of north-south hybrids in comparison with east-west. Relative humidity was higher in crop canopy as compared to top of the canopy in all the treatment combinations. Studies clearly showed that the crop microclimate provide valuable information regarding the interaction of the crop with its environment. The sowing date and orientation are two most important variables for evaluation of optimum microclimate of the crop for maximum growth and yield.