Effect of long-term fertilization on the phosphorus content of black soil in Northeast China

Samples of black soil were collected from long-term experimental plots in Gongzhuling to study the content and changing trends of soil phosphorus (P) under different fertilization practices (nonfertilization, chemical fertilization, organic fertilization and chemical plus organic fertilization). Results showed that contents of total P and available P in soil under no fertilizer treatment were lower than the other fertilization treatments. The application of organic fertilizer increased the content of total P and available P in 0-40 cm soil depth and content of total P and available P decreased with increasing soil depth, until no changes were found at 60 cm. Soil P had positive and significant correlations with soil total organic carbon and soil total nitrogen content because nitrogen and P were applied simultaneously. It also had negative and significant correlations with soil pH. Efficient use of phosphorus in organic manure and fertilizer require a balanced application of phosphorus.