Impact of foliar spray of agrochemicals on biophysical parameters, PAR interception and heat use efficiency of mungbean (Vigna radiata (L.) Wilczek) under variable sowing dates in Punjab, India

A study was carried out during kharif season of 2022 and 2023 at the Punjab Agricultural University (PAU)-Regional Research Station (RRS), Ballowal Saunkhri (SBS Nagar) with the objective to find out the impact of foliar spray of agrochemicals on biophysical parameters, PAR interception and heat use efficiency of rainfed mung bean (Vigna radiata (L.) Wilczek) under variable sowing dates. Timely sown crop (second fortnight of July) resulted in higher leaf area index, chlorophyll index, PAR interception and heat use efficiency (HUE) as compared to late sowing (first fortnight of August). Significantly higher seed yield, stover yield and biological yields were obtained in timely sowing during both the years of study. Foliar spray of KNO3 @ 1.5% recorded significantly higher leaf area index, chlorophyll index, PAR interception, heat use efficiency (HUE) and helio-thermal use efficiency (HTUE) but it was statistically similar with foliar spray of N:P:K (20:20:20) @ 1.5%. Foliar spray of KNO3 @ 1.5% and N:P:K (20:20:20) @ 1.5% gave statistically similar seed, stover and biological yields and significantly better than other treatments. There was an increase of 33.3% in seed yield with foliar spray of KNO3 @ 1.5% and increase of 29.1% with foliar spraying of N:P:K (20:20:20) @ 1.5%, when compared with control.