| Long-term agroecosystenm experiments with more than 20 years and a certain scale are used to study yield, nutrient cycling and environment effect during the process of agriculture. it can provide valuable information for biology, biogeochemistry and agricultural environmental assessment under conditions of routine agricultural management. Based on the Key Field Monitoring Experimental Station for Reddish Paddy Soil Eco-environment in Wangcheng, Ministry of Agriculture, China and Red Soil Experimental station in Qiyang, Chinese Academy of Agricultural Sciences, the evolvement rule of soil fertility and chemical behavior of heavy metal has been studied in this research. The results were as follow:Long-term application of chemical fertilizer, may lead to soil acidification, and nitrogen fertilizer is the dominated reason for red soil acidification. pH reduced after the long-term application of straw and pig manure in red paddy field while increased after the application of pig manure in red upland soil; it is a effective way to apply organic manure for enhancing CEC and soil organic matter content.The quantities of total nitrogen and available nitrogen enhanced by application of nitrogen, organic fertilizer and combined application of organic and inorganic fertilizer; soil phosphorus improved when phosphatic and organic fertilizer were applied. what’s more, available soil phosphorus of treatments which applied organic fertilizer are higher than treatments which applied chemical fertilizer alone; effects of soil total potassium by long-term fertilizer are not obvious. however, the available potassium highly improved after application of potash, organic fertilizer and combined-application of organic and inorganic fertilizer.The concentration of Cd of in red paddy field of each treatment in Wangcheng exceeded the limitation of secondary value of Chinese soil environmental quality standards, among which concentration of Cd of treatment that applied pig manure have exceeded tertiary value. Excepting the treatment of NP and NK, the concentration of Cd in red upland soil of each treatment in Qiyang have exceeded the secondary value, among which concentration of Cd of treatment that applied pig manure have exceeded the limitation of tertiary value. what’s more, concentration of Cu also exceeded the secondary value and Zn had a certain accumulation after application of pig manure. Which means that feces may be a important source of heavy metal pollution for agricultural soils.The main fraction of heavy metal after long-term fertilizer is residual fraction, and results show that the application of pig manure have great influence on speciation of heavy metal:compared with NPK treatment, total quantity of Cd were higher in the treatment of applying pig manure. What’s more, the increment of Cd by application of pig manure mainly transfer into residual fraction while Cu mainly transfer into reducible and oxidizable fraction and Zn mainly transfer into residuble, acidic and reducible fraction.The quantity of available Cu in red paddy field in Wangcheng increased by applying organic fertilizer, and quantities of available Cu, Cd enhanced by applying pig manure. However the relative availability of heavy Cd and Pb were reduced which may because that the solubility of Cd and Pb decreased by chelate organic matter. Whereas the solubility of Cu increased because Cu tend to combine with micromolecule organic acid which added its mobility.By the use of stepwise regression analysis, the main impact factors were analyzed. Results show that the quantity of available Cu is mainly affected by CEC and the amount of total Cu in soil and available Cd concentration is influenced by pH and total quantity of Cd in soil while concentration of available Zn show positive correlation with CEC and available Pb has negative correlation with pH and organic matter content. |
PDF Full Text Request