Decrease in soil inorganic nitrogen supply capacity under long‐term areca nut plantations in the tropics

Abstract

AbstractUnderstanding the dynamics and availability of soil nitrogen (N) affected by the conversion of cropping patterns is critical for environmental sustainability, especially in tropical soils with low fertility and high N loss. In this study, the 15N tracing technology combined with the 15N tracer model was used to explore the dynamic change of soil N transformation in long‐estabished areca nut (Areca catechu) plantations. Areca nut plantations with different ages (2, 5, 10, 14, and 17 years) and paddy fields in the tropical region of China were studied. The results demonstrated that the gross N mineralization rate (M) of areca nut plantation soil was much lower than that of paddy soil. The NH4+ immobilization (INH4) rate was also significantly reduced in areca nut plantations. Besides, the ONH4 (autotrophic nitrification) in long‐term areca nut planted soil decreased significantly with decreasing ammonia‐oxidizing archaea (AOA) and ammonia‐oxidizing bacteria (AOB) abundance. Inorganic N supply (INS) capacity of areca nut planted soil was much lower than the paddy soil, indicating declined N supply in long‐term areca nut plantations soil. The decline in soil gross N transformations rate and INS capacity of areca nut plantations soil was significantly correlated to reduced levels of TN and soil pH. Thus, agricultural practices that increase the soil pH (e.g., biochar or lime application) and the soil organic matter content (e.g., organic fertilizers) could improve soil INS capacity.