Effects of different mulching and fertilization on phosphorus transformation in upland farmland

In the present study, the impact of different soil surface mulching, fertilization on phosphorus mineralization and bio-availability of spring maize at various growth stages and soil layers (0-20 and 20-40 cm soil layer) were evaluated. The results indicated that the contents of total P and Olsen-Phosphorus (Olsen-P) in the soils of 0-20 cm soil layer were significantly higher than those in the 20-40 cm soil layer at different stages. The addition of organic fertilizer significantly increased the soil total P and Olsen-P content in the 0-20 cm soil layer. The different surface mulching, no mulching (NM), gravel mulching (GM) and film mulching (FM) were significantly affected by the content of Olsen-P in both soil layers during the critical growth period of spring maize. The Ca₁₀-P contents in both soil layers were the maximum in terms of the inorganic phosphorus content in soils with different surface mulching and different fertilization. Surface mulching significantly affected the transformation of inorganic phosphorus in different soil layers of dry-land farmland, and accelerated the increase of Ca₂-P content (first phosphorus source) in 0-20 cm soil layer by GM and FM. In addition, phosphorus combined with inorganic nitrogen fertilizer increased Ca₈-P (second Olsen-P source) to a certain extent, and reduced the relative content of Ca₂-P (first phosphorus source). Compared with phosphate (P), nitrogen and phosphorus (NP) treatments, manure and nitrogen and phosphorus (MNP) treatments increased the contents of Ca₂-P (first phosphorus source) and Ca₈-P (second effective phosphorus source), while it reduced the insoluble phosphorus source (O-P) content.