A New Index-Based Evaluation of Crop Sowing Windows across India

The crop sowing dates (CSDs) or windows are influenced by the climate conditions, cropping seasons, topography of a region, variety of crop, and other relevant factors. The present study emphasizes the drought-analysis-assisted identification of the optimal crop sowing date for two major cropping seasons (Kharif and Rabi) across the seven agroclimatic zones of India employing historical hydrometeorological data (HHD: precipitation and temperature) for 70 years’ time span. The trends in HHD may favor early sowing, late sowing, or prevailing sowing dates (ESDs, LSDs, or PSDs) and that needs to be analyzed. The Reconnaissance Drought Index (RDI) is calculated on seasonal basis by varying CSD (by −10 to +30 days with regard to PSD) across all the years. The analysis of drought occurrence (with varying CSDs) was conducted by estimating drought count under each category of drought classes, examining the trend of Mann-Kendall’s statistic of RDI values, and assessing the reliability and resilience of RDI series. A new index is introduced, based on averaged RDI values; its minimum value represents most suitable CSD. The results revealed that drought count decreases as the CSDs are shifted toward LSDs for the majority of considered cases (cropping seasons and climate zones). The trend in Mann-Kendall’s trend statistic of RDI series varying with CSDs exhibited a distinct upward trend as observed from ESD to LSD for a majority of cases, thereby agreeing with the inference in favor of selecting LSDs as optimum sowing dates. The reliability of the RDI series with regard to CSDs shows mixed patterns with minimal fluctuations in its magnitude. The variation in resilience with CSDs, notably the increase to a peak (when CSDs are near the middle of the LSD window) then decline toward late LSDs in most cases. This study is helpful in the strategic development of available water resources in satisfying agricultural needs by improving water availability during crop seasons.