Radiation and water use efficiencies of rainfed castor beans ( Ricinus communis L.) in relation to different weather parameters

Abstract

Field experiments on rainfed castor beans ( Ricinus communis L.) were conducted for 4 years (1990–1993) to explain the variability in radiation use efficiency (RUE) and water use efficiency (WUE) in relation to meteorological parameters. In these experiments castor c.v. Aruna was sown on three different dates (treatments) in each year. The results from this study indicate that both RUE and WUE vary from year to year and also were influenced by the planting dates. Variations in RUE and WUE ranged from 0.79–1.19 g MJ −1 and 0.72–1.25 g kg −1, respectively. The variability in RUE and WUE before and after flower initiation were quite contrasting. The variability in RUE and WUE was associated with saturation vapour pressure deficit (SVPD), drought index, temperature and wind velocity. RUE was related positively with SVPD and wind velocity and negatively with drought index and temperature. WUE showed inverse relationships with SVPD and temperature and a direct relation with wind velocity. The study emphasises the need for incorporation of the effect of weather on RUE and WUE in the algorithms for biomass estimation of crop simulation models.