Effects Of Land-use Systems Change From Paddy Field To Vegetable Land On Soil Properties And Its Environmental Impact

The phenomenon of paddy field being transferred vegetable land is a typical land use change with speedy urbanization in the Pearl River Delta area, which may cause many environmental impacts. In this paper, taking paddy field and vegetable land changed from former as research object, soil chemical properties evolutions and their environmental effects due to land use change was studied, by adopting field investigation and laboratory experiment, Furthermore, soil phosphorus loss potential was evaluated between the two land use patterns by laboratory experiment of simulation runoff and isothermal adsorption. Main results and innovations were followed:1. After land use change from paddy field to vegetable land, in addition to the contents of soil total nitrogen and organic matter decreased lightly, the total and available contents of else nutrient components including phosphorus and potassium, and partial trace elements B and Zn; the electric conductivity, total salt content and nitrate content increased more largely; the spatial distribution of soil nutrients and salinity was represented by more of them being transferred and leached to lower horizon. What's more, the soil properties variability of vegetable field was related to excessively employing fertilizer, using a little lime, and the process of plant management such as deeply cultivation and vegetable succession crop.2. The amount of Equilibrium P Concentration at Zero sorption (EPC₀), of Readily Desorped P (RDP), of Dissolved Reactive Phosphorus (DRP) and Bioavailable Phosphorus (BAP) was 10.4, 14.3, 2.5 and 3.6 times as much as that of the corresponding paddy field, which meant that vegetable farm soils would produce a greater risk for phosphorus loss than that of paddy field.3. The potential loss risk and the quantities of soil phosphorus transferred into water body mainly laid on soil supplying phosphorus level and degree of soil phosphorus sorption saturation (DPS) and following P-sorption capacity. Soil organic matter could play a buffering role on soil phosphorus loss. What's more, among all the parameters, M3-P and DPS gave better estimates of phosphorus loss potential between soil and water interface.