Recycling rice straw enhances the solubilisation and plant acquisition of soil phosphorus by altering rhizosphere environment of wheat

An in-situ, rapid, and low cost management of the huge amount of rice straw (RS) is a great challenge in south Asia. On the other hand, mobilisation of soil phosphorus (P) from inorganically fixed pools could improve its efficiency sustainably. To solve these problems concurrently this study was conducted to test whether the application of RS+P solubilizing microbes (PSMs) could solubilise a significant amount of the fixed P from soil and they could influence P transformation, silicon (Si) concentration, organic acid (OA) production, and enzyme activity in the rhizosphere to improve the yield of wheat. The specific objective of this study was to identify the sufficient amount of RS for solubilisation of fixed P to meet its demand to crops and develop a fertiliser application strategy accordingly. Application of RS (at 12 Mg ha())(-1)+PSM could solubilise similar to 2.96-3.26 % of inorganically fixed P in soil depending on soil temperature. It reduced the hysteresis effect by 10 % over control. Oxalic acid, citric acid, formic acid, malic acid, and tartaric acid could be identified in the rhizosphere of wheat. Application of RS (at 12 Mg ha())(-1)+PSM+ 75%P enhanced the activities of dehydrogenase, alkaline phosphatase activity, cellulase, and peroxidase by -1.80, 1.79, 2.14, and 1.40 times over control in the wheat rhizosphere, respectively, at maturity stage. It also enhanced the plant available P by 21 % over mineral fertiliser application during wheat growth. It also boosted Si concentration by 61 % over control in rhizosphere. Application of RS (at 12 Mg ha())(-1) +PSM+ 75%P resulted in a 45 % greater grain yield of wheat than control. It also improved root length, volume, and P uptake by 1.74, 2.40, and 1.61 times respectively over control. Path analysis indicated that P solubilisation by Si and OAs significantly contributed to P availability in the rhizosphere of wheat. Hence, RS (at 12 Mg ha())(-1) +PSM+ 75%P of mineral P fertiliser could be recommended to the cultivators for saving 25% P fertiliser without affecting yield.

Automated summary

The management of rice straw in south Asia is a challenge. This study found that the application of rice straw and phosphorus solubilizing microbes (PSMs) can solubilize fixed phosphorus in the soil, improve the yield of wheat, and increase organic acid and enzyme activity in the rhizosphere. The recommended application rate is 12 Mg ha-1 of rice straw and PSMs plus 75% mineral phosphorus fertilizer to save 25% of phosphorus fertilizer without affecting yield.