Effects Of Straw Turn-rotated Returning Field On Soil Physical Properties And Microbial Biomass And Soil Enzyme Activity

As a large agricultural country,China is rich in straw resources.With the increasing of yield of straw,a reasonable and effective straw processing method has become more and more important.Straw return as an important way to deal with crop straw has been study for many years.However,with the deepening of the study,the traditional straw return showed a lot of drawbacks:reduce crop seedling emergence rate and seedling growth;crops straw return too shallow and decompose fast,so is not conducive to the accumulation of soil carbon sequestration;it is not conducive to soil tillage layer deepening and so on.Therefore,to explore a more suitable way of straw return is essential.In this study,a 5.5 year field experiment was carried out with total straw returning in the following methods:straw turn-rotated return at the depth of 20 cm(D2),40 cm(D4)and CK(CK).The CK was defined as conventional tillage with no straw returning and tillage.Our objective is to explore the effects of straw turn-rotated return on soil physical properties,microbial biomass and enzyme activity.The followings are the results:1.Effects of straw turn-rotated returning field on soil physical propertiesD2 could reduce soil bulk density and increase total porosity compared with CK.The beneficial effects on soil structure will be held even in 4.5 years.With the increase of returning time,the effect is gradually decreasing.In the soil layer of 0-7 cm,the bulk density and total porosity of D2 and D4 are gradually close to CK.However,there were significant differences between both straw turn-rotated straw return depth and CK in the soil layer of 7-14 cm.In the case of high rainfall(26.6 mm),the water potential of D2 and D4 rose faster than CK in a short time.In the case of low rainfall(10 mm),the water potential of D4 rose faster than D2,and CK was slowest.It was found that 12 days after rainfall,the water potential of D2 and D4 decreased rapidly and lower than CK,the soil water potential of each treatment in 40 consecutive days was CK>D4>D2.The soil daily range at 0-15 cm soil depth was D2>CK>D4,treatment CK was highest at 20 cm soil depth.It increased the temperature of D2 at 0-15 cm soil depth and D4 at 0-20 cm soil depth,the temperature of D2 at 20 cm was closed to CK.2.Effects of straw turn-rotated returning field on soil microbial biomassD2 increased soil microbial biomass carbon in the 10 cm soil layers above and below straw layers,but reduced soil microbial biomass carbon in the soil of 0-10 cm.D4 increased soil microbial biomass carbon and bacteria in the 20 cm soil layers above straw layers and in the 10 cm soil layers below straw layers,but the soil microbial biomass carbon and bacteria in the soil of 0-20 cm was reduced.With the increase of returning time,the soil microbial biomass carbon of D2 in the soil of 0-10 cm and D4 in the soil of 0-20 cm were increased and closed to CK.D2 increased soil bacteria in the 10 cm soil layers above and below straw layers,but reduced soil bacteria in the soil of 0-10 cm.D4 increased soil bacteria around the straw layers especially in the 10 cm soil layers above and below it,while the soil bacteria in the soil of 0-20 cm was reduced.Two treatments had increased the amounts of soil fungus.The amounts of soil fungus of rice straw return declined rapidly at first and then increased gradually as the increase of returning time.The amounts of soil fungus of wheat straw return ware raise as the increase of returning time.D2 increased soil actinomyce in the 10 cm soil layers above and below straw layers,D4 increased soil actinomyce in the soil of 10-50 cm.If the straw returned time more than 30 month,the amounts of soil actinomyce in the soil of 0-10 cm of D2 and D4 were lower than that of CK,otherwise,it will higher than that of CK.3.Effects of straw turn-rotated returningfield on soil enzyme activityD2 reduces the 0-10 cm soil urease,invertase activity,but an increase of 10-20 cm and 20-30 cm of soil urease and invertase activity;D4 reduces soil urease,invertase activity in the soil of 0-20 cm,but an increase of soil urease,invertase activity in the soil of 20-50 cm.Two treatments have increased soil catalase activity.D2 increased soil phosphatase activity in the 10 cm soil layers above and below straw layers,and there were no significant effects on it in the 10-20 cm.D4 reduces soil phosphatase activity in the 0-10 cm,increased soil phosphatase activity in the 20-50 cm,but there were no significant effects on it in the 10-20 cm.