Abstract:The study focuses on phosphoru(P) fractions and transformation in calcareous soil in a 15-year experiment under organic, integrated and conventional production modes of greenhouse vegetables. The hierarchical extraction method of inorganic P was used to analyze the distribution of inorganic P fractions. The results showed that production mode, fertilization year and their interaction all had significant effects on the contents of organic P and inorganic P fractions. With the increase of fertilization year, the contents of organic P, Ca2-P, Ca8-P and Fe-P under three production modes were continuously increased, but the contents of Al-P, O-P and Ca10-P changed irregularly with small variances. The contents of organic P, Ca2-P, Ca8-P and Fe-P under organic production mode were higher than those under integrated and conventional production modes, while the contents of O-P and Ca10-P under organic production mode were lower than those under integrated and conventional production modes. The proportion of P fractions was in an order of moderate-activity P sources (Ca8-P, Fe-P, Al-P) > potential P sources (O-P, Ca10-P) > available P source (Ca2-P). Organic P content accounted for 8%-23% and 6%-13% of total P content in 0-20 and 20-40 cm soils, respectively. The organic production mode could promote the transformation between inorganic P fractions and between organic P and inorganic P fractions, and it was more active in 0-20 cm soil than in 20-40 cm soil.