Growth and evapotranspiration pattern of rajmash (Phaseolus vulgaris L.) under varying irrigation schedules and phosphate levels in a hot sub-humid climate

Soil water and phosphorus availabilities play crucial role in yield and water use pattern of pulse crops. A field experiment with rajmash (Phaseolus vulgaris L.) as a test crop was carried out during the winter seasons of 2003–2004 and 2004–2005 on a sandy loam soil (Aeric Haplaquept) in eastern India. In the main plots, irrigation was applied when the cumulative pan evaporation reached: (i) 33 mm (CPE33), (ii) 44 mm (CPE44) and (iii) 66 mm (CPE66). In sub-plots, four levels of phosphate fertilizer were applied at: (i) 0 (P0); (ii) 30 (P30); 60 (P60) and 90 kg P2O5 ha−1 (P90). Irrespective of crop growth stage, the highest leaf area index (LAI), biomass, grain yield and water use efficiency were obtained under the combination of CPE33–P90. Magnitude of these parameters, in general, decreased with the decrease in irrigation frequency and phosphate levels. With the advancement of crop growing period, cumulative actual evapotranspiration (CAET) increased linearly. Best matching between CAET and cumulative pan evaporation data was recorded under CPE33–P90 treatments. A linear relationship with high coefficient of determination was obtained between total biomass and CAET. Present study showed that crop response factor (ky) of the crop was 1.91.