Influence Of Different Fertilizr Treatments On Dynamics Of Dissolved Organic Matter And The Activity Of Copper And Cadmium In The Farmland Soil Under Rice-Wheat Rotation Cultivation

The water-dry cultivation is an important agricultural pattern in Yangzi river catchment area and the southeast area of China. Applying various organic manures in the farmland is a common agricultural practice under water-dry cultivation. It was documented well that the application of organic manures would increase the concentration of dissolved organic matter (DOM) in soils. DOM is an important component of the active organic carbon pool in terrestrial ecosystem. It plays an important role in the mobilization and translocation of soil heavy metals. Behaviors of heavy metals in the soil were of great concern due to their toxicity. Bioavailability and mobilization of heave metals depend, to a great extent, on their chemical forms which would be affected by DOM. The aim of this study was to investigate DOM dynamics and its distribution in the different depth of soil under water-dry cultivation with the additon of different organic manures by field micro-plot trials. Besides, environmental behavior of soil-born copper and cadmium in soil facilitated by DOM was also studied in present study.It was noted that the concentration of DOM in pig manure- and/or green manure-treated soils was increased drastically both in paddy soil and drought soil, as compared to the contro lwith the addition of fertilizer only. DOM concentration in soils decreased with the increase of time after application. The concentration of DOM was highest in the depth of 0 to 20 cm and decreased with depth both two soils. In rice growing season, DOM in soil could transfer to the depth of 80 cm at least. But in wheat growing season, DOM only migrated into 40 cm depth in soil profile. The translocation ability of DOM in drought soil for wheat growing season was obviously weaker than that in paddy soil for rice growing season. DOM concentration in rice- or wheat-rhizosphere soil was similar to bulk soil or non-rhizoshpere soil at initial growing stage, but DOM concentration...