RESUMO
In this study, topsoil samples were collected from wetlands recovered from farmlands respectively for 3, 5, 9 and 11 years around Caizi Lake, Anhui, China. Their characteristics of adsorption and desorption of phosphorus were examined with comparison to soils sampled from an adjacent vegetable farmland and a non-cultivated wetland. Phosphorus adsorption curves of all studied soils could be modeled by Langmuir and Freundlich equations (P < 0.01). The maximum P adsorption (Xm), adsorption constant K and maximum buffer capacity (MBC) of all the 6 soil samples were in the ranges of 478-1074 mg x kg(-1), 0.14-0.61 and 68.6-661.5 mg x kg(-1), respectively. These three parameters all tented to increase with the recovered years but did not reach the values of the non-cultivated wetland. However, the P desorption rate ranging from 6.2% to 14.6%, increased first and then decreased with the recovered years and was significantly higher than that of the non-cultivated wetland. It was concluded that the P immobilization would increase with the recovery years of cultivated wetlands, which could be affected by the soil organic carbon and clay contents of the wetland soil.
