Adsorption and transport characteristics of liquid animal manure-derived dissolved phosphorus in four soils

High concentrations of dissolved organic matter (OM), dissolved organic phosphorus (P) and inorganic P can be input into agricultural soils in the form of applied animal manure. Understanding the relative mobility and interactions of those dissolved matter in the soils is necessary to manage P in agricultural system. In this study, solution containing dissolved OM, dissolved organic P and inorganic P was separated from an liquid animal manure, four soils (two samples of quaternary red clay, one sample of desalted muddy polder soil, and one sample of fluvio-sand ridge soil) with different texture and OM were collected. The isotherm adsorption and leaching experiments were carried out to study the adsorption and transport characteristics of the liquid animal manure-derived dissolved inorganic and organic P in the soils under the co-existence of dissolved OM, dissolved organic P and inorganic P. The adsorption experiment showed that the existence of dissolved OM in high concentration decreased the soil capacity to adsorb inorganic and organic P, suggesting that application of liquid animal manure posed a greater risk of P losses from the soils than application of chemical fertilizers. The adsorption capacity of the soils to adsorb inorganic P was larger than that to organic P. However, the adsorption capacities of the soils to adsorb either inorganic P or organic P decreased in the order of quaternary red clay desalted muddy polder soil fluvio-sand ridge soil, and were related to contents of clay and iron oxides. The soil with a high content of OM had lower capacity to adsorb organic P than the soil with low content of OM. Leaching experiment showed that preferential adsorption sequence of the three dissolved matter in the soils was dissolved inorganic Pdissolved organic carbon dissolved organic P, organic P had higher mobility than inorganic P in the soils.