Soil inorganic phosphorus fractions under different modes of fertilization

A field trial was carried out to determine the inorganic P fractions under 8 modes of fertilization in the lower reach of Liaohe River Plain. The results showed that after 15 years of continuous cultivation, Ca₂-P, Ca₈-P and Al-P were influenced remarkablely by fertilization, while Fe-P, O-P and Ca₁₀-P were not, which indicated that the former were active in soil inorganic P pool, while the latter were inert. The direct influences of Ca₂-P and A1-P on available P were significant, whereas those of Fe-P and Ca₈-P were almost close to zero by the path coefficient analysis. While the indirect effects of Fe-P and Ca₈-P to available P were high. O-P and Ca₁₀-P had little effect on available P both in correlation analysis and path coefficient analysis.