Two strains of Luteovulum sphaeroides (purple nonsulfur bacteria) promote rice cultivation in saline soils by increasing available phosphorus

Abstract

Saline soils reduce available phosphorus, retarding plant growth, and rice is particularly affected. We evaluated the ability of purple nonsulfur bacteria to resist the acidic-sodium conditions in saline acid sulfate soil and saline soil, and their ability to enhance rice growth and grain yield by releasing normally unavailable phosphorus. Two P-solubilizing Luteovulum sphaeroides strains were applied to rice seedlings in a soil pot experiment. Single cultures and a mixed (1:1) culture of the strains increased rice growth and grain yield up to 10% in saline acid sulfate soil and 18% in saline soil. After harvest, both inoculated soils showed significantly increased pHH2O but significantly decreased electrical conductivity. The increase in Pavail in both inoculated soils resulted in higher accumulations of P in the rice plants. The need for chemical P fertilizer was reduced by 50% of the recommended application. Both inoculated soil types showed significant increases in NH4+ and potassium. Sodium concentrations in both inoculated soil types were significantly lower than in controls. Proline content in rice from both inoculated soil types was also significantly lower. Rice grain yields were proportional to the inoculated bacterial populations.