Impact of Low Molecular Weight Organic Acids on Soil Phosphorus Release and Availability to Wheat

Phosphorus (P) use efficiency (FPUE) is very low due to fixation of P with the hydrous oxides of iron and aluminum in acid soils and calcium in neutral to calcareous soil. The roots of wheat (Triticum aestivum) excrete low molecular weight organic acids (LMWOAs) to increase P bioavailability in P-deficient soil through acidification, chelation, and exchange mechanisms. However, the amount of LMWOAs excreted in the rhizosphere is small, and they undergo rapid microbial degradation. The present study was undertaken by applying different levels of LMWOAs and phosphorus to the soil followed by sowing of wheat seeds to learn the impact of applying LMWOAs, especially oxalic (OA) and citric acid (CA), on the yield and FPUE of wheat. The results showed that application of P fertilizer along with OA and CA significantly increased the Olsen P concentration in soil and in turn increased P uptake, FPUE, and yields of wheat. Application of OA @ 15 mg kg(-1) recorded 20% (+/- 0.22%) and 30% (+/- 0.55%) higher grain and straw yield, respectively, over control and was more effective than CA. Among LMWOAs, application of OA @ 15 mg kg(-1) was more effective than CA. Therefore, the application of OA has the potential to reduce the excess application of phosphorus and its buildup in soils and cause eutrophication of water bodies.