Impacts of Molybdate Unreactive Phosphorus on Phosphate Release from Intensively Fertilized Soil

Abstract

Total phosphorus (P) in soil is classified as molybdate-reactive P (MRP) and molybdate-unreactive P (MUP) based on bioavailability, and P tests are generally focused on MRP fraction of soil, despite the fact that MUP can contribute significantly to total extracted P. This survey study indicated that water-soluble P (WP) contributed as much as 9% to total P (TP) in two intensively fertilized (rice–onion cropping upland and greenhouse) soils, and most (ca. 80%) of WP was present in MUP form. The total P lost through runoff and leaching was high (>5 ppm), due to rotating greenhouse into submerged paddy soil, especially at the initial stage of rice cultivation, and MUP contributed 43% and 77% to total P lost through runoff and leaching, respectively. Therefore, it is necessary to monitor MUP to develop suitable soil-management strategies to reduce MUP release and P loss from high-P-containing soils.

Keywords:

• Dissolved phosphorus
• molybdate-reactive P (MRP)
• molybdate-unreactive P (MUP)
• phosphorus release

Acknowledgment

This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science, and Technology (2013028761).