Effect of phosphorus on drought mitigation and productivity of rainfed upland rice (Oryza sativa)

Abstract

The effect of phosphorus application at varying rates, viz. 0, 12, 24, 48 and 96 kg/ha, was studied on drought mitigation and productivity of two upland rice (Oryza sativa L.) varieties ('Vandana' and 'Annada') during 1999, 2000 and 2001 under rainfed upland condition at Hazaribag in Jharkhand. Phosphorus was applied basal through single superphosphate along with common doses of N, K, Zn and Mg. The effects of P rates, and interac- tion effects between P rates and varieties were significant in the drought year only (2000). Reduction in grain yield due to drought in no-P plots was 27.4% in 'Vandana' and 58.4% in 'Annada' in comparison with normal rainfall year (1 999). The grain yield of 'Annada' and 'Vandana' decreased by 11.7 and 25.4 at 24 kg Plha, and by 2.5 and 5.2 at 48 kg P/ha respectively. Maximum P-use efficiency was achieved at 24 kg P/ha in both the variet- ies. Concentration of P in grain and straw was also reduced due to drought in 2000 at low P application com- pared with that in 1999. Differences in agronomic P-use efficiency were apparent due to varieties. Agronomic P- use efficiency was 38.1 kg graintkg P in 'Annada' compared with 15.5 kg graintkg applied P in 'Vandana'. How- ever, differences due to varieties in relative effect of drought stress (RDS) and available soil P were marginal. It was concluded that the application of P @ 24 kglha helped in reducing the effect of drought as well as in in- creasing the rice productivity and P-use efficiency of rainfed upland rice.