Requirement of rice crop for phosphorus and potassium at varying sodicity levels

Abstract

Rice (Oryza sative L.) plants were grown in pots in soil at pH 8.0, 9.4 9.8, and 10.0 to study the response to phosphorus (P) and potassium (K) fertilization at the rate of 60 kg/ha alone or in combination on growth, yield attributes, and chemical composition of the shoot. Increasing sodicity stress (pH 8.0, 9.4, 9.8, and 10.0 achieved by using sodium bicarbonate) adversely affected growth with delayed initiation of tillering and reduced the grain filling period. Total and filled grains per panicle, 1,000 grain weight, and grain yield were significantly lowered even at pH 9.4. Analyses of the shoot at 30 days after transplanting and at maturity showed a pronounced increase in Na concentration with a decrease in ? and calcium (Ca). Phosphorus and magnesium (Mg) were slightly higher in the shoot in response to sodicity stress. Fertilization with ? and ? at pH 10.0 helped plants to offset the ill effect of sodicity by early initiation of tillering and flowering and had a positive response on the yield attributes and grain yield. This also resulted in a decrease in Na and improvement in the ? and ? status of shoot. It was concluded that the amount of available ? and ? in the soil which was adequate for plant growth and development at lower sodicity levels, however became inadequate at higher sodicity.