Liming and Phosphate Application Influence Soil Carbon and Nitrogen Mineralization Differently in Response to Temperature Regimes in Allophanic Andosols

Andosols are characterized by high organic matter content and play a significant role in carbon storage. However, they have low phosphorus fertility because of the high phosphate-fixing capacity of active aluminum. For agricultural use of Andosols, it is necessary to ameliorate its poor phosphorus fertility by applying lime and high doses of phosphate fertilizers. The objective of the present study was to clarify how such soil amendments affect the mineralization of soil organic carbon (C) and nitrogen (N) in allophanic Andosols under different temperature regimes. The soil was treated using combinations of liming and heavy phosphate application, followed by incubation under different temperature conditions. The N mineralization and the soil CO2 evolution rate were measured periodically. The patterns of N mineralization were analyzed by fitting them to first-order kinetics. Liming increased C and N mineralization irrespective of temperature, and the increase was further enhanced by phosphate application. Kinetic analysis of the N mineralization curve indicated lowering of the activation energy of N mineralization reactions with phosphate application, suggesting that P application may accelerate N mineralization at lower temperatures. These findings provide a basis for developing soil management strategies to reduce the loss of soil organic matter.