Impact of low molecular weight organic acids on soil Olsen phosphorus and its phyto-availability to soybean (Glycine max)

Abstract

Soybean crop is used as both legume and oil seed contributing for 23% of total vegetable oil production of the country. Soybean productivity and fertilizer P use efficiency (FPUE) is low due to its higher fixation with iron, aluminum and/or calcium minerals in the soil. In order to make the fixed P bioavailable, plant roots secretes low-molecular weight organic acids (LMWOAs) which act as ligands and compete with the PO₄^3– site of Fe²⁺, Al³⁺, and/or Ca²⁺. But the LMWOAs secreted by crops are of very low concentration and also these LMWOAs undergo rapid degradation in the soil. Therefore, present study was undertaken to know the impact of extraneous application of LMWOAs (oxalic and citric acid) on yield of soybean. Results showed that the application of LMWOAs significantly increased the soil Olsen P concentration and soybean yield. Application of LMWOAs (10 mg LMWOAs kg⁻¹) along with 9 mg P kg⁻¹ can reduce about half of the recommended dose of P fertilizers (RDPF i.e., 18 mg P kg⁻¹) through increased FPUE without compromising the yield. By enhancing FPUE, LMWOAs indirectly reduce cost of cultivation and avoid environmental imbalance. However, higher concentration of oxalic acid drastically reduced yield of soybean by damaging its root system.

Keywords:

• Low-molecular weight organic acids
• oxalic acid
• citric acid
• P use efficiency
• soybean