Effects of different manures on phosphorus adsorption and desorption of a reclaimed mining soil

Objectives The reclaimed calcareous soil is extremely low in P, and the applied P is easily immobilized by cations. The effects of various manures on P adsorption and desorption in reclaimed soil were studied to provide a theoretical foundation for rapid soil reclaimation in a mining area.

Methods A fertilizer field experiment was conducted in a coal mining subsidence reclamation soil located in Xiaoyi City, Shanxi Province for four years, the fertilizer treatments included three manures (chicken, pig, and cow manures) and two chemical fertilizers (NP and NPK), and the no fertilizer control, with the same total P input (100 kg/hm²). The soils were collected from the treatment plots for isothermal adsorption and adsorption incubation experiment. Additionally, the relationship between the soil physico-chemical properties and the characteristic parameters of P adsorption and desorption was examined.

Results The P adsorption curve was well fitted by the Langmuir equation (R²=0.924−0.992). Both reclamation years and fertilization, and their interaction had significant effects on P adsorption and desorption. As reclamation years increased, the maximum adsorption capacity of P decreased by 12%−26%, while the P adsorption saturation and P desorption rate increased by 218%−885% and 86%−118%, respectively (P<0.05). Compared with chemical fertilizer treatments, the manures reduced the maximum adsorption capacity and buffer capacity of P by 30% and 31%, and increased the adsorption saturation and desorption rate of P by 34% and 16%−24%, respectively. Among the three manure treatments, their effects on P adsorption were in order of pig manure>chicken manure>cow manure, and desorption were in order of chicken manure>pig manure>cow manure. The results of redundancy analysis (RDA) showed that total P and organic matter were the main factors affecting P adsorption and desorption, explaining 74% and 13% of the total variation, respectively (P<0.01).

Conclusions Fertilization reduced soil P adsorption while increased P desorption capacity, and the effect of manures were more remarkable than chemical fertilizer even at the same amoFertilization reduced soil P adsorption while increased P desorption capacity, and the effect of manures were more remarkable than chemical fertilizer at the same input amount in the reclaimed mining soil. Total P and organic matter strikingly influence the n saturation increased rapidly with the fertilization years, the soil P adsorption and desorption characteristics should be monitored for the risk of environmental degradation.