Abstract:

【Objective】 Response of Olsen-P to P balance in a black loessial soil was studied in a long-term fertilization experiment carried out in Pingliang, Gansu province for the purpose of providing a theoretical basis for the scientific application of phosphate fertilizer in the Loess Plateau dryland farming areas. 【Method】 The relationships between Olsen-P change and the budget of soil P balance in the treatments of CK, N, NP, M, NPM were studied by the method of linear regression based on a 28-year (1979-2007) experiment. 【Result】 The results showed that long-term application of M, NP, and NPM resulted in significant increase of Olsen-P by 0.54, 0.64 and 1.11 mg?kg-1?a-1, respectively. While the soil Olsen-P content remained stable or showed a decreasing trend in the CK and N treatments. The increase amount of Olsen-P changed with P balance. Application of NP, M, NMP increased the amount of Olsen-P significantly. The P balance was very significantly (P＜0.01) correlated with the Olsen-P. With an average surplus of 100 kg phosphorus per hm2, the soil Olsen-P increased by 3.85, 0.29 and 0.53 mg?kg-1, in the NP, M, and NPM treatments, respectively. Application of chemical fertilizer increased Olsen-P was 11.6 times higher than that of manure, followed by the chemical fertilizer combined with manure. 【Conclusion】 Changes of soil Olsen-P followed soil phosphorus surplus and the close correlation between the increased amount of Olsen-P and the form applied phosphorus were observed. Long-term application of chemical P fertilizer resulted in the increase of the amount of Olsen-P is higher than manure obviously in black loessial soil.

Key words: long-term fertilization, black loessial soil, Olsen-P, P balance