The Effect Of Chinese Milk Vetch And Other Organic Mateirals’ Application On The Loss Of Nitrogen And Phosphorus And The Activity Of Heavy Metals In Paddy Soil

As the acceleration of industrialization and population growth, we are confronted with animportant issue: the protection of soil resource and its sustainable utilization. Theresearches on eutrophication and the soil accumulation of heavy metals are the two hotresearch areas of environmental scientists nowadays. Fertilization is a kind ofindispensable measure for the high crop yield. Cooperation of chemical fertilizer andorganic fertilizer is a kind of environmental friendly way of fertilization, which canimprove soil structure and its nutrient supply, reduce the loss of nitrogen and phosphorus,but there may be some potential risks too, such as the long-term risk of potential nutrientloss, the activation of heavy metals in paddy soil, etc. This research focused on theeffects of reducing the loss of nitrogen and phosphorus and the form transformation ofheavy metals in paddy soil under the treatments of Chinese Milk Vetch and other organicmaterials in paddy soil. The results are as follows:1. A group of field experiments, with same amount of NPK and different organicmaterials input, were carried out in typical rice planting area in Ningshao Plain,Zhejiang Province, to study the effects of reducing the N, P loss in paddy soil underdifferent organic materials’ treatments. The six treatments: chemical fertilizer,Chinese Milk Vetch (52.5t·hm^-2), commercial organic fertilizer (6t·hm^-2), straw(9t·hm^-2), Chinese Milk Vetch (26.25t·hm^-2)+commercial organic fertilizer(3t·hm^-2), Chinese Milk Vetch (26.25t·hm^-2)+straw (4.5t·hm^-2). The resultsshowed: compared with chemical fertilizer treatment, all the five organic materialtreatments can reduce the loss of nitrogen and phosphorus in different extent inpaddy field: the loss of inorganic nitrogen reduced27.7%⁴4.3%, the soluble-Preduced13.0%³6.9%in the runoff water; in the leaching water, inorganic nitrogenreduced28.0%⁴3.3%, soluble-P reduced3.7%³2.9%. Among the five organicmaterial treatments, Chinese Milk Vetch and （Chinese Milk Vetch+organic fertilizer）are the two better ways in reducing the loss of nitrogen and phosphorus in the runoffwater, but for the leaching water, Chinese Milk Vetch and straw treatments are betterthan others.2. A group of pot experiments, with same amount of NPK and heavy metals input （Cu:400mg·kg-1, Zn:500mg·kg-1）, was carried out in Zhejiang Soil&Fertilizer andEnvironmental Science Observation Experiment Station of Ministry of Agriculture, P.R. China, to study the effects of the form transformation of heavy metals in paddysoil and the plant’s absorption of heavy metals under three kinds of fertilizers:chemical fertilizer, Chinese Milk Vetch(52.5t·hm^-2), commercial organic fertilizer(6t·hm^-2). The results showed: compared with chemical fertilizer treatment, theheavy metals’ validity was increased under the Chinese Milk Vetch treatment, whilethe commercial organic fertilizer treatment reduced the heavy metals’ validity. TheCu&Zn content was increased in rice straw, but the Cu content in brown rice wasreduced under the Chinese Milk Vetch treatment. The commercial organic fertilizer treatment reduced the Cu content in rice straw and brown rice, but increased the Zncontent in rice straw.3. With the same volume of Chinese Milk Vetch added to soil, a group of rice potexperiments was carried out under different concentration of Cu and Zn, to study onthe effects of the form transformation and rice absorption of heavy metals. Theresults showed: all the different forms’ concentration of heavy metals ascended as theheavy metals addition increased in soil through all the rice growth period, but theheavy metals’ concentration in rice straw and chaff descended as the heavy metalsaddition increase in soil. The results also showed, the Cu and Zn content in rice strawwas lower than 《Tolerance limit of copper in food》and 《Tolerance limit of zinc infoods》.