The Effect Different Ways Of Straw Returned On Available Phosphorus In Soil Under The Condition Of Freezing And Thawing

Straw returning can affect the availability of soil phosphorus by changing the physical and chemical properties of soil and soil environment.In the northeast of China,the soil structure have changed due to the repeated freezing and thawing in spring.But the present reports about straw input on freeze-thaw reported effectiveness of brown period effect and mechanism of phosphorus are rare.In this experiment,through simulation test,research and analysis of different applying methods under different gradient after straw returning soil available phosphorus and the related nature of changes in the freeze-thaw process,the straw soil nutrient status of the growth of early spring crops in Northeast china will be investigated.The results of this study have some guiding significance in the practice and theory of biochar returning in Northeast China.The main conclusions are as follows:(1)The content of available P in soil can be significantly increased by the segment and the powder field,but the increase of the straw powder is obvious under the same amount of application.In the experiment,the content of available phosphorus in soil was not stable at the first 5 cycles of freeze-thaw cycles,and the content of the available phosphorus gradually is stabilized with the freeze-thaw test.The available phosphorus contents of two kinds of treatments were soil at about fifth times when the peak,the available phosphorus applied straw and straw powder section in the soil the average contents were 22.23 mg.kg-1,22.97 mg.kg-1,19.58%and 23.56%compared to those without increasing freeze-thaw respectively.(2)After straw returned directly,under the same applied amount of straw returned to the field,the phosphatase activity of CK<was applied to the straw stalk.In the same way,the phosphatase activity in soil was CK<2%<4%<6%.In the whole process of freeze-thaw cycle,the variation of electrical conductivity of three kinds of straw returned to field was similar to that of phosphatase activity.The correlation between the content of available P and phosphatase activity and electrical conductivity of the two types of straw returned to the field reached a significant level.On the whole,the influence of conductivity on Phosphorus in the process of freezing thawing is greater than that of phosphatase.(3)At the end of culture by the straw pyrolysis into biochar,the effective phosphorus content increased with the increase of biochar application rate,and the effective phosphorus content was increased by more than 20%compared with the control treatment,with the application of biochar(2%,4%,6%).The results showed that the peak value of available phosphorus increased with the increase of the amount of biochar applied in fifth treatments.After twentieth freeze-thaw cycles,the available phosphorus content of each treatment was relatively higher than that of the valley,and the content of available phosphorus was decreased by 18.9%,8.2%,and 9.5%,respectively,by the application of biochar to the treatments of 2%,4%and 6%.(4)Analysis of the biological carbon input of brown soil pH value,conductivity,organic matter and other biochemical properties of phosphatase activity in response to freezing and thawing,The results showed that the addition of biochar had no significant effect on the content of soil organic matter in the 5-30 freeze-thaw cycles.The effects of freezing and thawing on soil pH and organic matter content were significant,but there was no significant effect on electrical conductivity and phosphatase activity.The organic matter content,electrical conductivity and the content of available phosphorus were positively correlated at each stage of freeze-thaw cycle.(5)Contents of available phosphorus in soil were higher than no straw returning,and the same applies and the overall content of available phosphorus in soil volume is SS<PS<BS,whether it is a kind of way in returning the soil available phosphorus contents are:the amount of 6%>4%>2%>CK,and the change for the first time 3-5 increased slowly until the rapid increase to the peak then decreased slowly at last gradually stabilized.