Effects of the coupling water and fertilizer on soil phosphorus components in alfalfa field in Eastern Inner Mongolia, China.

Abstract

Soil phosphorus (P) could be categorized into organic and inorganic forms, with diffe-rent capabilities of nutrient supply. Exploring soil P components through liquid 31P-NMR would provide an important theoretical basis for soil P nutrition regulation. This study addressed the characteristic of P in alfalfa (Medicago sativa) soil via the pot experiment. There were two scenarios of treatments with conventional and dry water combined with different P fertilizer levels (P0-P4: 0, 0.025, 0.05, 0.1, and 0.2 g P2O5·kg-1soil). The characteristics of P components in alfalfa soil under water-fertilizer coupling conditions were measured by liquid 31P-NMR. Results showed that under different water and fertilizer treatments, soil inorganic P was mainly composed of inorganic orthophosphate, pyrophosphate and inorganic polyphosphate. Inorganic orthophosphate was the dominant component of inorganic P, which could be reduced by drought. High P application (P4) could increase the contents of soil inorganic polyphosphates and inorganic pyrophosphates. Among the organic P components, monoester orthophosphate was dominant, the conversion and utilization of which in alfalfa soil were affected by drought. Overall, the rational management of water and fertilizer could effectively regulate the conversion and utilization of P nutrients in alfalfa soil in Eastern Inner Mongolia.