Effects Of Different Tillage On Soil Organic Carbon And Microbial Biomass Activities In Oasis Irrigation Area

For the waste of water resources caused by flood irrigation in traditional cultivation methods,increase consumption and mineralization of soil organic carbon decomposition, soil microbialactivity is reduced and the soil quality degradation；the tractor in the field walking, resulting in largeareas of soil compaction, soil tillage resistance phenomenon. Comb ined with laboratory analysisbased on field experiments on the long-term locating field plots was established in2005in oasisirrigation area in Hexi Corridor to study the change of the soil organic carbon and soil microbialactivity of different till ages including conventional tillage （CT）, fresh raised-bed （FRB）, permanentraised-bed （PRB） and zero tillage with control traffic on flat field （ZT）. The following conclusions:1. The distribution characteristics of soil total organic carbon and particulate organic carboncontent under different tillage treatment in the soil profile were similar. The differences of TOC andPOC contents among the four tillage systems were obvious in the plow layer and graduallydecreased with the increase of soil depth. Two controlled traffic farming （PRB and ZTtreatments）TOC and POC content is obviously higher than that of conventional tillage,PRBtreatment on the largest contribution to the improvement of TOC and POC content on the top layerof soil,the second is ZT treatment,PRB treatment TOC and POC content increased by3.42%24.54%and3.42%32.64%than CT treatment, ZT treatment TOC and POC content increased by1.22%19.03%and0.69%22.04%than CT treatment,FRB treatment TOC and POC contentincreased by-0.33%8.22%and-8.17%14.38%than CT treatment. The positive correlationdistinguishedly was appeared between TOC and POC in soil,POC variation coefficient is higher,that impact of tillage farming to the POC is more sensitive.2. PRB treatment significantly increased soil microbial biomass carbon, nitrogen andphosphorus content. Four kinds of tillage treatments on soil microbial biomass carbon and nitrogenin the soil are characterized by PRB> ZT> FRB> CT, the differences in the top layer is especiallysignificant,soil microbial biomass carbon of PRB,ZT,FRB and CT were1325.53mg/kg,1258.33mg/kg,1181.63mg/kg and1129.67mg/kg, compared with CT treatment, PRB, ZT and FRBprocessing soil microbial biomass carbon were increased195.86mg/kg,128.66mg/kg and51.96mg/kg,soil microbial biomass nitrogen of PRB, ZT, FRB and CT were36.09mg/kg、33.94mg/kg、31.06mg/kg and29.30mg/kg，compared with CT treatment, PRB,ZT and FRB processing soil microbial biomass nitrogen were increased23.17%、15.84%�'�6.01%；With the changing rule of thesoil microbial biomass carbon, nitrogen is different,Soil microbial biomass phosphorus is sensitiveto environmental conditions,controlled traffic farming have a bigger influence on the surface soilmicrobial biomass phosphorus content,Four processing PRB, ZT, FRB, and computed tomography（CT） soil microbial biomass phosphorus content were109.13mg/kg,103.86mg/kg,98.60mg/kgand96.46mg/kg. Compared with CT, PRB, ZT and FRB treatment soil microbial biomass pincreased by13.13%,7.67%and13.13%. Four kinds of soil microbial biomass C/N had nosignificant difference in the same soil, soil microbial biomass C/P is increased along with the soildeepens.3. The distribution characteristics of soil enzyme activity under different tillage treatment inthe soil profile were gradually decreased with the increase of soil depth. soil catalase activity ofPRB, ZT, FRB and CT were62.16mg g^-1、60.87mg g^-1、59.90mg g^-1and59.53mg g^-1,there is nosignificant difference, controlled traffic farming significantly affected soil catalase activity in toplayer, and under40cm the effect of the controlled traffic farming on soil catalase activity is small.Soil invertase activity of PRB, ZT, FRB and CT were78.88mg g^-1、75.41mg g^-1、69.98mg g^-1and66.39mg g^-1, soil urease activity of PRB, ZT, FRB and CT were9.35mg g^-1、8.86mg g^-1、8.36mg g^-1and8.02mg g^-1, controlled traffic farming significantly improved the0-60cm soil layersoil sucrase and urease activity. The relationship between soil enzyme activity showed that the threekinds of enzymes are reached significant level and there is an extremely significant positivecorrelation between TOC、POC and microbial biomass with them （especially sucrase and urease）,and shows that soil invertase and urease activity in soil carbon and microbial biomass contributionis bigger.4. Soil respiration rate of PRB, ZT, FRB and CT in0-20cm soil layer were231.77mg kg^-1d-1、215.67mg kg^-1d-1、263.79mg kg^-1d-1and280.45mg kg^-1d-1.Soil respiration rate among the fourtillage systems in the soil profile in followed the order of0-5cm>5-10cm>10-20cm, soil respirationrate of PRB, ZT, FRB and CT in0-5cm soil layer were113.33mg kg^-1d-1、109.22mg kg^-1d-1、103.15mg kg^-1d-1and106.32mg kg^-1d-1, conventional tillage treatment and controlled trafficfarming soil basic respiration rate were little changed. soil basic respiration rate in5-20cm followedthe order of CT>FRB>PRB>ZT; the differences is apparent, compared with the other threetreatments, CT treatment significantly increased the content of2.70mg kg^-1d^-110.78mg kg^-1d-1、 26.80mg kg^-1d^-128.88mg kg^-1d-1and33.04mg kg^-1d^-134.63mg kg^-1d-1.Correlation analysis showedthat0-5cm soil basic respiration and soil carbon,soil microorganism quantity and enzyme activitywere a positive correlation between relations and5-20cm were negatively correlated betweenrelations.