Monitoring of productivity and crop water stress in pearl millet using theSPAW model

For assessment of soil water in the Indian arid zone, the profile soil mois ture content in pearl millet, grown under optimum moisture and rainfed cond itions at jodhpur, was simulated using the SPAW (Soil-Plant-Air-Water) mode l for seven cropping seasons during 1990 to 1996. The simulated profile soi l moisture content was close to the observed data, both under optimum moist ure and rainfed crop conditions, as well as when crop was sown under late ( 1992), early (1993) and normal (1994) conditions, with RMSE (root mean squa re error) values ranging between 0.62 and 1.83. The Water Stress Index (WSI ). calculated using the SPAW model, had a linear, but. inverse relationship with the productivity of pearl millet (Y, kg ha(-1)). The regression equat ion between them was Y= -258.9 WSI + 3847.2 (R-2=0.94) and was useful for p earl miller yield estimation in the Indian arid region.