Monitoring of late-season agricultural drought in cotton-growing districts of Andhra Pradesh state, India, using vegetation, water and soil moisture indices

Persistent soil moisture deficits during flowering and yield formation stage are referred to as late-season agricultural drought. This study aims to assess late-season agricultural drought in cotton-and millet-growing districts of Andhra Pradesh, India, during summer cropping season 2011. Satellite-based indices like the Normalized Difference Vegetation Index, Normalized Difference Water Index and their Vegetation Condition Index from MODIS were analyzed. The root zone Soil Moisture Index (SMI) using soil water balance model for cotton and millet (sorghum and pearl millet) crops was derived to evaluate the soil moisture status. The analysis was carried out by comparing the satellite-derived indices with the previous normal years, and the assessments were made. The satellite-based indices clearly brought out the stress that the crop endured during late October and November, while SMI indicated soil water stress in early October. The soiland crop-specific SMI's were able to clearly indicate the exact period of water stress. The results show that millet crop was able to escape drought due to sufficient rainfall and its shorter duration, while cotton crop did not have enough soil moisture during the critical stage of flowering and boll formation and suffered severe yield loss due to the late-season agricultural drought.