The Application And Technology Of Soil Improvement Under Crop-Livestock System In Agricultural Soil

With the rapid development of industry and agriculture,soil pollution and degradation increasingly emerged.According to our investigation and previous literatures,the main problems of the degraded soil in Shanghai suburb were organic matter,nutritional imbalance,contaminant accumulation,salinization and biological function recession.As we all know,waste can be effectively utilized in integrated crop-livestock system,thus not only leads to reduced pollution,but also to improved soil quality.In this study,experimental bases were located in Zhongxin and Yonghe farm of which the core of crop-livestock system were different,and simulation and field experiments were carried out to alleviate soil heavy metal pollution,recycle agricultural waste and optimize organic tillage management,aims at reviving the degraded soil functions.The main conclusions are as follows:?1?Geostatistical analysis and denaturing gradient gel electrophoresis?DGGE?were undertook in a littoral farming system in eastern China to examine the changes of the soil chemical properties and the bacterial community diversity that occurred during the transition phase?1-2 year?in which the cropping system changed from conventional farming to organic farming.Results indicated that compared with that of the soil in conventional farming,the SOC,TN,AC,and AN of the soil in organic farming increased by 90-140%,33-108%,and 60-140%in 0-20 cm,20-40 cm and 40-60 cm soil depth,respectively.Significant inter-correlation?P<0.01?were shown in properties of the soil of0–20 and 20–40 cm depth.Besides these,even under the same cropping systems,the properties of the soil showed apparent changes,which indicates that the soil chemical properties were instability in space and susceptible to the environmental interference during the transition phase,and appropriate measures should be took in the early stages.?2?As for the Zhongxin farm,most soil properties were moderately dependent?Nugget/Sill between 25%-75%?.The spatial distribution map of soil properties produced by Arcgis can guide the precise fertilization for farm manager.Though soil EC values in this region were high(maximum 2450?s cm^-1),EC values in rice-upland rotation(1100?s cm^-1)were lower than that in upland tillage(1250?s cm^-1),which suggest that in order to avoid causing new soil salinization,special attention should be paid on soil salt condition in coastal saline area when carried out organic cultivation.DGGE showed that bacterial community diversity was highest in paddy-upland rotation soil,and bacterial community diversity was more correlated to the cultivation type than the fertilizer type.Thus it could be concluded that conservation organic tillage can increase the content of organic carbon and nitrogen in soil,and can also maintain the abundant diversity of soil bacterial community during the transition period of organic farming.?3?Livestock was the production core in integrated crop-livestock system of the Zhongxin farm,and after 2 years operation,it was noticed that superabundant livestock waste must be composted in time to avoid secondary pollution.In order to accelerate the efficiency of waste utilization,composting experiments were carried out.Results showed that addition of straw degradation microorganisms?JFB-1?could significantly improved the temperature?5-10??in the composting process and short the fermentation period?1-2day?.Due to the high temperature of fermentation,the pathogenic microbes in the compost materials could be effectively killed,which in turn improved the quality of the composts.Contents of soil organic matter,total nitrogen,cellulase activity were generally improved after adding these composts.?4?Different from the Zhongxin farm,the production core in crop-livestock system of the Yonghe farm was planting,and the main use of livestock was to supply the nutrient requirements of the crops.Insufficient livestock manure caused by small livestock proportion and secondary pollution of waste were the primary problems of the Yonghe farm.In this study,system dynamics was used to optimize the livestock proportion and results showed that when the marketable fattened stock of the pigs reached 1800,the nutrient demand of crops could be meet,as well as the soil pollution be reduced at the greatest extent.Soil remediation in Yonghe farm were integrated with multi-disciplinary technologies such as system analysis,waste recycling,precise fertilizer,crop rotation,crop sequence arrangement,sewage purification etc..The soil microbial number and soil nutrient had been improved after 3 years remediation.The maximum of the organic matter,total nitrogen,available phosphorus and available potassium increased by 52%,109%,2624%and 52%,respectively.Soil pH gradually approached to 7 and EC value greatly reduced,indicating that not only the crop yield was increased but also the risk of salinization was reduced because of the remediation.As for those heavy metals in the soil,Cu showed fluctuation with increasing cultivation years,and Cd,Pb,Cr appeared a slight increase,while Hg and Se revealed a downtrend.However,all the heavy metal levels were near or lower than the soil background value,which ensured the safety of the agricultural products.Through correlation analysis,Cd,Cu,Cr,and Pb showed significant positive correlation?P<0.01?with organic matter,and Cd showed obvious positive correlation?P<0.01?with cultivation year,which suggested that during organic cultivation,special attention should be paid on avoiding the accumulation of these heavy metals and soil pollution should be strictly controlled from source.?5?In order to reduce the accumulation of Cd and Pb in soil in crop-livestock farm,Cd/Pb-resistant fungi and citric acid?CA?were introduced to enhance the phytoextraction of the Solanum nigrum L.in a greenhouse pot experiment.The accumulation of Cd and Pb in S.nigrum and the soil enzyme activities of dehydrogenase,phosphatase,urease,catalase,sucrase,and amylase were determined.Results showed that the addition of fungi,CA,or their combination could improve the ability of accumulating heavy metals of the S.nigrum by enhancing its root biomass.Compared with those untreated S.nigrum,contents of Cd and Pb in the S.nigrum that treated with CA and fungi increased by 22–47%and13–105%,respectively.Meanwhile,activities of most of the enzymes were also enhanced after the remediation,and the improvement effect were in the order of phosphatase,amylase,catalase,dehydrogenase,and urease as analyzed with DCCA ordination graph.These results suggest that fungi and CA-assisted phytoextraction is a promising approach to restoring heavy metal polluted soil.