Relationship of Agro-Meteorological Indices with Cotton Yield under Varied Pre-Sowing Irrigation Levels, Sowing Dates and Time of First Irrigation in North-Western India

ABSTRACT Irrigation water scarcity during the very high rate of evapotranspiration period (during May and June) is a major concern for cotton production in north-western India. So, an experiment was planned to study the response of cotton to levels of pre-sowing irrigation, different times of sowing, delay in first irrigation and different agrometeorological indices (AMI). Cotton growth and yield attributes and AMI for different phenophases were poor under shallow pre-sowing irrigation and resulted in a reduction in seed cotton yield (SCY) significantly by 14.4–15.7% as compared to heavy pre-sowing irrigation. Timely sown cotton achieved maximum crop growth and yield attributes and AMI as well as SCY over the late sown crop. Late sown crop resulted in more than 40% yield reduction. Cotton crop that received first irrigation at 4 weeks after sowing (WAS) recorded significantly higher SCY along with higher growth and yield attributes and AMI. A delay in first irrigation from 4 WAS to 6 WAS resulted in the reduction of 15% SCY. SCY was significantly correlated with accumulated growing degree days (GDD), phenothermal index (PTI) and helio-thermal units (HTU) with higher correlation coefficients. Hence, higher AMI, SCY and heat use efficiency (HUE) were achieved from early sown crop with heavy pre-sowing irrigation and first irrigation at 4 WAS.