Abstract
Soil salinity has adverse effects on soil microbial activity and nutrient cycles and therefore limits crop growth and yield. Amendments with halotolerant phosphate-solubilizing bacteria (PSB) and rock phosphate (RP) may improve properties of saline soil. In this study, we investigated the effects of RP either alone or in combination with PSB (Providencia rettgeri strain TPM23) on peanut growth and soil quality in a saline soil. With the combined application of RP and PSB, plant length and biomass (roots and shoots) and uptake of phosphorus (P), nitrogen (N), and potassium (K) increased significantly. Soil Na+ and Cl– contents decreased in the PR alone or PR combined with PSB treatment groups. There were strongly synergistic effects of RP and PSB on soil quality, including a decrease in pH. The soil available N, P, and K contents were significantly affected by the PSB treatments. In addition, the alkaline phosphomonoesterases, urease, and dehydrogenase activities increased significantly compared with the untreated group; highest alkaline phosphomonoesterases activity was observed in the RP and PSB treatment groups. The composition of rhizosphere soil bacterial communities was determined using 454-pyrosequencing of the 16S rRNA gene. In the PR alone or PR combined with PSB treatment groups, the structure of the soil bacterial community improved with increasing richness and diversity. With PSB inoculation, the relative abundance of Acidobacteria, Chloroflexi, and Planctomycetes increased. The three phyla were also positively correlated with soil available N and root dry weight. These results suggested microbiological mechanisms by which the combined use of RP and PSB improved saline soil and promoted plant growth. Overall, the study indicates the combined use of RP and PSB can be an economical and sustainable strategy to increase plant growth in P-deficient and salt-affected soils.
Highlights
Saline soil is a serious global environmental problem that negatively affects agricultural production because of unfavorable soil physicochemical properties and nutrient deficiencies (Shrivastava and Kumar, 2015)
When rock phosphate (RP) was combined with phosphatesolubilizing bacteria (PSB) inoculation, shoot and root dry biomass were significantly affected by PSB inoculation (Figure 1A)
The results showed that PSB application significantly increased soil bacterial populations and favored those phyla that were associated with soil nutrient cycling
Summary
Saline soil is a serious global environmental problem that negatively affects agricultural production because of unfavorable soil physicochemical properties and nutrient deficiencies (Shrivastava and Kumar, 2015). Most P in soil is in inorganic and organic forms with low solubility that are not available for plant uptake (Adnan et al, 2017). The use of microbial inoculation combined with rock phosphate (RP) is recognized as a suitable strategy to improve saline soil properties and plant growth (Singh and Reddy, 2011); Phosphate-solubilizing bacteria (PSB) are an integral component of the soil P cycle and play a key role in dissolving different pools of soil P to increase P availability to plants. The main mechanism underlying inorganic phosphate mineralization is the production of lowmolecular-weight organic acids These acids acidify phosphate conjugate bases, thereby increasing their solubility as a result of the reduction of soil pH, while chelating metals (Wei et al, 2018). Few studies have explored the potential of halotolerant PSB to dissolve multiple P sources
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