Co-application of biochar and salt tolerant PGPR to improve soil quality and wheat production in a naturally saline soil

Abstract

Soil salinity is a global problem that drastically reduces crop productivity. Therefore, there is a need to make saline soils productive. Plant growth promoting rhizobacteria (PGPR) and biochar have been shown to increase crop productivity and soil fertility when applied separately. However, their co-application in this regard has not been studied extensively. In this study, a biochar was co-applied with Bacillus thuringiensis or Bacillus tropicus, characterized as P-solubilizing and salt-tolerant PGPR, to wheat grown in a naturally saline soil (EC 8.12 dS m−1). Co-application of biochar with PGPR increased the number of tillers & spikes, straw yield, and 100-grain weight by 16–28.57%, 26.9–36.6%, 18–21.8%, and 34–37.9% respectively. This led to a 37% and 34% increase in grain yield in the case of co-application with B. thuringiensis and B. tropicus respectively. The higher growth and yield were thanks to better plant nutrition and mitigated salinity stress under co-application. Briefly, the co-application increased phosphorus content in grain, straw, and roots by up to 9–43%, 45–69%, and 5–21.5% respectively, which was higher than that in individual applications of biochar or any PGPR. In addition, co-application increased microbial biomass by 61–77% and soil available phosphorus by 37–53% across two PGPR. Evidently, the co-application contributed to increased P nutrition in two ways. Firstly, the biochar itself served as a source of available P. Secondly, the PGPR solubilized it more abundantly when biochar was there. As far the salinity stress, biochar, its co-application with B. thuringiensis, and with B. tropicus increased soil K+/Na+ by 36%, 72% and 44% respectively leading to 40%, 63%, and 55% higher K+/Na+ in grain, straw, and roots respectively. Overall, our results indicate that biochar and PGPR worked in tandem to substantially improve soil quality and wheat production compared to their sole applications. We conclude that co-application of salt tolerant PGPR and biochar is a more sustainable and better technology to produce wheat in a naturally saline soil compared to their sole applications.