Influence of irrigation frequencies and phosphate fertilization on actual evapotranspiration rate, yield and water use pattern of rajmash ( Phaseolus vulgaris L.)

Abstract

The hypothesis was tested, whether soil wetness and phosphorus status could regulate the evapotranspiration rate (ET R), which is of special interest in the lower Gangetic Plain. Rajmash was grown during November–February of 2003–2004 and 2004–2005 on a sandy loam soil, and was irrigated when cumulative pan evaporation (CPE) attained the value of 33 mm (CPE 33); 44 mm (CPE 44) and 66 mm (CPE 66). Four levels of phosphate application were 0 kg P 2O 5 ha −1 (P 0); 30 kg P 2O 5 ha −1 (P 30); 60 kg P 2O 5 ha −1 (P 60) and 90 kg P 2O 5 ha −1 (P 90). Seed yield under CPE 33 was 1.37 Mg ha −1 and reduced by 18% and 35%, respectively under CPE 44 and CPE 66. Continuous increasing trend in yield was recorded with an increase in phosphate level (PL). Irrespective of growth stages, similar trends were recorded for leaf area index (LAI). Maximum variation in LAI among the treatments was recorded at 60 days after sowing. On average, actual ET R was 1.37 mm day −1 under CPE 33 and declined by 13% and 16% under CPE 44 and CPE 66, respectively. Variation in ET R under different PL was highest under CPE 33 and lowest under CPE 44. Except P 90, irrespective of PL, highest value of water use efficiency (WUE) was obtained under CPE 44. However, magnitude of net evapotranspiration efficiency (WUE ET) and irrigation efficiency (WUE I) attained the highest level under CPE 33 regime. All water use indices showed an increasing trend with the increase in phosphate level from 0 to 90 kg ha −1. Impact of phosphorus on various parameters was pronounced under CPE 33.