The effects of summer maize
residue (MR) and winter wheat residue (WR) applied alone or in combination with fertilizer P (FP) on the characteristics of phosphate
adsorption and forms of phosphorus in a calcareous soil were carried out in a 15 week long incubation study (keeping constant at 10
mg P
kg~(-1)). The results showed that either MR, WR alone or in combination with fertilizer P could decrease the P adsorption
capacity and increase the P availability. The magnitude of increase in NaOH-Po and NaOH-Pi of MR and WR alone by 6.0 and 5.6mg kg~(-1) against CK, and NaOH-Po was by 12.7 mg kg~(-1) at the end of 15 week long incubation. A linear form of the
Langmuir equation was used to evaluate the P adsorption maximum, bonding energy constant, P adsorption buffer capacity and the standard Prequirement. These values all differed significantly between treatments, and the highest was found for the CK, and the lowest for the MR. It indicated that these two kinds of crop residues promoted P availability in calcareous soil.