Effect Of Organic Materials On Black Soil Aggregate And Organic Carbon Content

Soil degradation in the black soil region of Northeast China is mainly manifested in yearly decrease of organic matter content,which is a potential threat to regional ecological environment and national food security;thus,it is necessary to find an effective way to improve the structure of black soil and increase the content of soil organic matter so as to promote the farmland productivity.Based on farmland soil of erosion and deposition areas from typical black soil region of Northeast China,the effect of three common exogenous organic materials(straw,biochar and swine manure)on soil aggregate distribution,stability and organic carbon content were comparably analyzed by using in-lab constant temperature and humidity incubation method.The difference of soil response to exogenous organic materials in erosion and deposition areas was further analyzed.The purpose of this study is to provide scientific evidence for restoring erosion-degraded soil and the main findings are as follows:1)For erosion area,the addition of straw and swine manure could significantly increased the>2 mm size aggregates content,and significantly decreased the 0.053～0.25 mm size aggregates content,and then enhanced the mean weight diameter(MWD)and geometric mean diameter(GMD)of water-stable aggregates,and the effect became better with the increase of the addition amount.A moderate amount of biochar can significantly increased the content of 0.25～2 mm aggregates and decreased the content of 0.053～0.25 mm aggregates,but high amount of biochar addition was not conducive to the formation of macroaggregates(>0.25 mm).The addition of straw,biochar and swine manure could increased the total soil organic carbon content in the erosion area,in particular,the larger the amount of biochar,the better the improved effect.In addition,all three organic materials addition can effectively increased the organic carbon content of each size aggregates,however,the improvement of organic carbon content of>2 mm size aggregates by biochar was not significant.2)For deposition area,addition of straw and swine manure could effectively increase>2mm size aggregates content,and the effect became better with the increase of the addition amount,and decreased the 0.053～0.25 mm and<0.053 mm size aggregates content,at the same time,can both significantly enhanced the MWD and GMD values of water-stable aggregates.The addition of biochar significantly increased the content of 0.25～2 mm aggregates,decreased the content of 0.053～0.25 mm and<0.053 mm aggregates,but did not effectively enhance the stability of water-stable aggregates.The addition of straw and swine manure could not effectively increase total soil organic carbon content,in particular,adding straw significantly reduced the organic carbon content of>2 mm aggregates.The 0.25～2 mm and 0.053～0.25 mm sizes aggregate-associated organic carbon content were significantly increased only when the addition amount of biochar was at high level.3)The enhancement effect of soil aggregate stability after adding organic materials was better in the deposition area than in the erosion area.For deposition area,straw addition was the best,followed by swine manure,and the effect of biochar was not obvious.Adding straw and swine manure had the better effect on soil amendment in the erosion area.On the contrary,the amendment effect of adding organic materials on total soil organic carbon content in the erosion area was better than that in the deposition area,and the amendment effect of biochar was better than that of straw and swine manure.This study can provide a theoretical basis for reasonable selection of fertilization measures,improvement of black soil structure and enhancement of black soil productivity.Further field experiments should be carried out in the future,and the effectiveness of the three exogenous organic materials in improving the quality of black soil should be further studied.