Enhancing phosphorus availability in calcareous soil through the incorporation of organic acids

Plants cultivated in calcareous soil exhibit phosphorus deficiency, resulting in diminished crop productivity and reduced yield quality. In order to enhance phosphorus availability in soil, the introduction of organic acids represents a viable strategy. Consequently, a controlled incubation experiment was carried out to investigate the impact of organic acid supplementation on phosphorus availability in calcareous soils. The experiment involved the addition of three organic acids (citric acid, ascorbic acid, and tartaric acid) at varying amounts (15, 25, and 35 mmol/kg soil) to a calcareous soil supplemented with phosphate fertilizer (diammonium phosphate) at a constant level of 50 kg P/ha. The soil samples were subjected to incubation at a temperature range of 17-20°C at field capacity moisture content for varying durations of 15, 30, 45, and 60 days. The measurements of accessible phosphorus, total phosphorus, and soil pH were conducted following each incubation period. The findings of the study indicated a significant rise in the concentration of available phosphorus and a corresponding decrease in total phosphorus and pH levels throughout the experiment when organic acids were introduced. Among the organic acids tested, citric acid exhibited the most favorable outcomes, particularly at a concentration of 35 mmol/kg soil resulting in the highest phosphorus availability. The administration of organic acids may have contributed to an increased buildup of phosphorus in its organic form. Hence, the utilization of organic acid has the potential to augment the accessibility of phosphorus in calcareous soils and alter the balance between mineralization and immobilization, favoring the enrichment of the organic fraction of phosphorus rather than the relatively more stable mineral calcium phosphates. This has the potential to improve the long-term availability of phosphorus in calcareous soils.