| By studying on the transfer of N,P,K in soil-plant ecosystem,and their environmental effects, this paper aims at finding the optimal application ratio of sewage sludge compost and chemical fertilizers, which may supply theory and practical guide for the garden utilization of sewage sludge.This research investigated the performance of potted experiment and field experiment of corn Using the compost by dewatered sewage sludge from Chongqing Beibei Water Quality Purifying Factory and straw. The mix rates of the compost with the fertilizer were 1:3,1:1 and 3:1The potted experiment results and conclusions can be summarized as follows: Crops straw sludge compost can promote mineralization of nitrogen significantly in soil. the contents of nitrogen and nitrate were improved further by sludge composts with straw and wheat than that composts with straw and corn. so it will be lower by compost with YCC and XMC than that with SDC and YMC. The First-order kinetics equations for describing N mineralization dynamic in compost treated soils show that it can be significantly improved No that imposed sludge compost. The max valuer of No was YCC which improved in lime purple soil and yellow soil, XMC was improved in acidic soil and lime soil.it can be suggested that nitrogen will be added in soil at nearly 30d when sludge compost added in yellow for the crop growth.it will be added in soil as available N to fit the crop growth. field experiment results and conclusions can be summarized as follows:(1) the different ratio of sludge compost with straws and chemical fertilizers,the contents of ammonia and nitrate could be higher than others when the ratia of sludge compost with cron and chemical fertilizers was 1:3.the ratio of SDC and chemical fertilizers was 1:1,the contents will be higher than others so.(2) Straw sludge compost and fertilizer was mixed by different proportions can promote the mineralization of P. the contents of organic P can improve higher significant.two type of straw sludge with fertilizers was 1:1 proportion.when the ratio of fertilizers and YMC was 3:1,the contents was most than others in acid soil.(3) It can be improved the mineralization of K than different ratio of sludge compost and fertilizer.the soil properties can affected the contents. the ratio of fertilizer and YMC of SDC was 1:1 can improved mostly than others. the ratio was 1:3 in yellow soil.(4) The different ratio of compost and fertilizer can reduced pH in soil and improved content of organic matter.(5) When the fertilizer and compost add in soil with different ratio, the best ratio of fertilizer and YMC was 3:1 in yellow soil. the best ratio of fertilizer and YMC or SDC was 1:3 in yellow soil.(6) The absorption of plants was Cd>Pb>Cr, when sludge compost add in yellow soil, it was Pb>Cd>Cr in acid soil. the contents of heavy metal was max in plant when the ratio of sludge compost and fertilizer was 1:1.The paper analyzed the positive and negative effect of corn taking nitrogen, phosphorus, heavy metal into consideration. it could be concluded from effect that optimal application rate of sludge compost is 1:1 as fertilizer and SDC in yellow, the optimal ratio of fertilizer and YMC was 1:3.
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