Enhancement of rice growth and yield in actual acid sulfate soils by potent acid-resistant Rhodopseudomonas palustris strains for producing safe rice

Aims Purple nonsulfur bacteria (PNSB), Rhodopseudomonas palustris strains (TLS06, VNW02, VNW64 and VNS89), were investigated to increase rice growth and grain yield in acid sulfate soils (ASS) with low available phosphorus (P-avail). Methods P-solubilizers were tested in vitro. A 4 x 3 factorial design consisted of PNSB at 5.4 x 10(4) cells g(-1) dry soil weight (mixture of 4 strains, VNW64 singly, or no-PNSB) and P fertilizer levels (0, 30, 45 and 60 kg P2O5 ha(-1)) that were used with the rice variety OM5451in pots with two types of ASS (Hon Dat and Phung Hiep). Results The four PNSB mixture had the ability to dissolve insoluble P from variscite and strengite. The combination of mixed culture with 45 P was the most effective, increasing grain yield by 34%. Enhancement of rice growth and yield in both soils corresponded to the maximal levels of P-avail, total P and NH4 (+), and the lowest levels of Al-exch and Fe2+. Soil health with this treatment was significantly improved, with a strong positive correlation between PNSB population and phosphatase activity in both soil types. Conclusions The combination of PNSB mixture with P fertilizer reduced the amount of chemical fertilizer needed for maximal grain yield, provided safe rice, and maintained soil health.