Biofertilizers from Rhodopseudomonas palustris strains to enhance rice yields and reduce methane emissions

Abstract

Flooded rice fields either organic or saline share common problems of low productivity and emission of methane (CH4) that contributes to global warming. Among various biofertilizers, purple nonsulfur bacteria (PNSB) are of good candidates to solve such problems since they could promote rice growth and yield, and also compete with methane producing bacteria for substrates. The goals of this work were to investigate the potential of Rhodopseudomonas palustris strains TN114, PP803 and TK103 identified as a biofertilizer to enhance rice yield and reduce CH4 emissions in both types of the rice fields. The efficiency of each PSNB biofertilizer were compared with a commercial organic fertilizer (COF), a carrier control (carrier with no added PNSB), and control without the addition of any fertilizer (control). In both paddy fields, no significant difference in the growth of rice was found based on the maximal height of plants, but there was a significant difference in rice grain yields. In saline paddy field, all PNSB biofertilizers produced higher grain yield at statistically significant level; however, in the organic paddy field only TN114 biofertilizer showed a promising result at 48% increase followed by COF treatment. The lowest grain yield was observed in both controls. COF treatment generated the highest CH4 emissions followed by both controls, and the least was in PNSB biofertilizer treatments, particularly PP803 which was 24% and 28% lower than COF in organic and saline paddy fields, respectively. Both paddy fields showed a strong negative correlation between PNSB cell density and CH4 emissions (rp=−0.90). It can be concluded that all biofertilizers from the selected R. palustris were able to enhance rice yields in both the organic and saline flooded paddy fields and concurrently reduce CH4 emissions.