Effect Of Organic Materials Addition On Resistance Of Black Soil To Mechanical Disturbance

The black soil region is an important commodity grain production base with the highest degree of agricultural mechanization across China.During long-term and frequent mechanical production,the tillage equipment can directly apply to the soil,which results in less stability of soil aggregates and further aggravates the risk of soil erosion.To find out whether added organic materials can enhance the ability of black soil to resist mechanical disturbance in cultivated land.Based on the farmland soil from typical black soil region under long-term mechanical operation,the constant temperature-humidity culture experiment were set up after adding three different exogenous organic materials（straw,biochar,swine manure）with different content gradients,and then mechanical disturbances of four intensities were conducted to explore the effect of organic materials on resistance of black soil to mechanical disturbance by using tradition and Le Bissonnais methods with three disintegration mechanisms（fast wetting（FW）,slow wetting（SW）,and wet stirring（WS））.The main results are as follow:1、Straw and swine manure significantly improved the stability of soil aggregates in traditional wet condition,and the effect increased with the addition amount and decreased with the mechanical disturbance intensity.The mean weight diameter（MWD）of soil aggregate after adding straw was 1.40 and 1.23 times of biochar and swine manure,respectively.Organic material amendment and mechanical disturbance both have the significant effect on>1 mm aggregate.The>1 mm aggregate is most sensitive to mechanical disturbance and organic material amendment for cultivated land.2、After fast wetting treatment,exogenous organic materials increased the content of large aggregates,improved the stability of aggregates and enhanced the soil to resist mechanical disturbance in varying degrees,and the effect of straw and swine manure was better than biochar.The MWD of biochar,straw and swine manure treatment was 1.13,1.20and 1.15 times that of CK,respectively.The aggregates stability increased with the addition amount,and the straw treatment was the most sensitive.The macro aggregates(R_0.25),mean weight diameter（MWD）and geometric mean diameter（GMD）of swine manure and straw decreased with mechanical disturbance intensity,but the treatment of biochar was opposite.The percentage of aggregate destruction（PAD）decreased with the disturbance intensity after adding exogenous organic materials.3、Compared with CK,biochar,straw and swine manure significantly improved R_0.25,MWD,GMD and reduced fractal dimension（D）and PAD in slow wetting.The MWD of biochar,straw and swine manure treatment was 1.11,1.19 and 1.17 times that of CK,respectively.Therefore,three organic materials enhanced ability of soil to resist mechanical disturbance,and the enhancement effect of straw and swine manure were better than biochar.Aggregates stability increased with the adding amount of biochar and straw,while aggregates stability of swine manure decreased with the adding amount.The R_0.25,MWD and GMD increased with the disturbance intensity after adding organic materials,and D and PAD decreased with the disturbance intensity.4、Biochar,straw and swine manure improved the stability of aggregates and the ability of soil to resist mechanical disturbance in wet stirring,and effect of swine manure was better than straw and biochar.The MWD of swine manure treatment was 1.06 and 1.07 times higher than that of biochar and straw,respectively.The aggregate stability of biochar and straw increased with the amount and mechanical disturbance intensity,and the treatment of swine manure was opposite.Straw and biochar were more sensitive than swine manure.This study indicated that exogenous organic materials could enhance the ability of soil to resist mechanical disturbance.The effects of different types and amounts of organic materials on improving the ability of soil to resist mechanical disturbance were different.This study can provide a theoretical basis for improvement of black soil structure and enhancement of black soil productivity.