Assessing critical weather conditions for optimal Kharif maize yield in Punjab

Maize is a vital cereal crop primarily grown during the kharif season. Although it is a short-duration crop (approximately 90 days), it is highly sensitive to abrupt changes in weather conditions. To better understand this, a study was conducted to determine the critical thresholds of temperature, relative humidity, and rainfall by analyzing meteorological data (collected from meteorological observatories) and crop data (2004-2018) from three locations in Punjab (collected from statistical abstracts). Over the 15-year period, three high-yield years were identified for Ludhiana (>5000 kg/ha), Ballowal Saunkhari (>4200 kg/ha), and Amritsar (>4000 kg/ha), and meteorological data for crop growth stages were tabulated accordingly. Weekly deviations of each meteorological parameter from normal data were computed. The stage-specific critical limits of these parameters were then validated using actual yield data from the crop years 2019 and 2020. In 2019, medium yields were observed, as temperature (Tmin) and relative humidity (RHmax) exceeded the upper threshold during the flowering and grain filling stages. In contrast, a high yield of 4376 kg/ha was recorded at Ballowal Saunkhari in 2020, as temperatures remained consistently within the optimum range, accompanied by well-distributed rainfall. The results indicated that for higher maize productivity, the optimal ranges for temperature and relative humidity at various crop stages are as follows: during germination, 36-40°C (max) / 21 27°C (min) and 30-55% RH; during vegetative growth, 31-41°C (max) / 24-30°C (min) and 55-75% RH; and during flowering to grain filling, 31-37°C (max) / 21-27°C (min) and 60-85% RH. Additionally, a well distributed rainfall between 500-600 mm is ideal for maize growth in Punjab.