Effect Of Straw Burning On Composition Of Soil Organic Matter And Aggregate

In recent years, caused by straw burning phenomenon of environmental problems has become a hot issue in the world of common concern. Not only because of straw burning gas emissions of harmful gases and pollute the atmosphere, but also the high temperature of burning have some influence to farming soil ecological environment. But, for the moment, at home and abroad it is still very scarce that the research on the impact of farming soil ecological environment of straw burning. This study based on the burning of corn straw covering soil as the main research object, aim at "Ping-pu burning" and "Cheng-pu burning" two burning ways in the corn field in Northeast of China, and chose field straw burning experiment combined with laboratory thermal radiation simulation experiment as technology route, the purpose was to discuss the characteristics of straw burning, changes of physical properties, organic carbon content and composition and aggregates composition in the soil after straw burning. The results showed that:(1) In the straw burning, the Cheng-pu burning was higher than Ping-pu burning with thermal radiation temperature on surface; on soil physical properties, both of two ways of straw burning make topsoil moisture content decreased, increased hardness, and significant changed in soil color.(2) Two ways of straw burning significant impacted on soil organic carbon content only on 0-2cm depth of topsoil, and both of them made the topsoil organic carbon content was significantly reduced, and the Cheng-pu burning was more significant; With increasing heat temperature, the soil organic carbon content trend to gradually decreasing, and in the temperature range of 200 ℃~360 ℃, it has the largest falling range, and compare with non-heating, the organic carbon loss rate was increased rapidly from 8.6% at 200 to 83.34% ℃at 360 ℃.(3) Both of two straw burning methods could increase the topsoil extraction rate of humus; with increasing heating temperature, the extraction amount and rate of humus tend to increased and then decreased, and the maximum amount of humus extract appeared at 200 ℃, the maximum extraction rate of humus appeared at 240 ℃; To the Cheng-pu burning, the extraction rate of humus had been basically reached the maximum. In the composition of humus, different ways of burning has different influence of humus composition, but in the content of each humus composition, the Cheng-pu burning significantly lower than the Ping-pu burning; In the HA / FA ratio, the Cheng-pu burning was higher significantly, and When the temperature at 240 ℃, the HA / FA ratio reached the maximum; The influence of heat on combined humus was significantly less than the free humus. The soil humification degree was increased after two ways of straw burning, and the content of active part in the soil humus was decreased, and the soil humus tend to aging, and in the Cheng-pu burning, the free state of soil humic acid type was changed; when the heating temperature at 300 ℃, the soil humification degree reached the highest, and when the temperature at the range of 240 ℃~300 ℃, the free state of soil humic acid type prone to change.(4) Under field conditions, both of two ways of straw burning made the content of soil dissolved organic carbon increased on 0-2cm surface soil; with increased heat temperature, the dissolved organic carbon content of soil tend to increased and then decreased, and when at the heating temperature with 200 ℃, the content of soil organic carbon was maximum and it increased 1.6 times than the unheated soil.(5) Two kinds straw burning mode only influence on 0-2cm surface soil aggregates composition, and Cheng-pu burning is more significant. Straw burning makes soil micro-aggregate structure tend to accumulate for small granule. After the straw burning the soil dispersion coefficient significantly increased, which Cheng-pu burning improved 33.82% ~ 58.23%, while Ping-pu burning improved 13.50% ~ 23.01%. In organic-mineral complex composition, only Cheng-pu burning affected significantly. To Cheng-pu burning, the clay and fine sand content decreased, silt content increased. Under two kinds of burning, the carbon storage capacity of each granule organic-mineral complex composition significantly lower than non-burning, and their organic carbon content in the clay and fine sand complexes reduced, while in silt complex organic carbon content increased, thus straw burning damage the structure of the soil micro-aggregates, reduce the microstructure water stability of the soil.