Effects Of Cultivation Period On Soil Aggregate And Organic Carbon In Horqin Sandy Land

In order to find out the effects of cultivation period on the stability and organic carbon of soil water-stable aggregates,this study analyzed distribution of aggregates with different particle sizes of corn fields with different tillage period and the sandy grassland nearby in the 0-40 cm soil layer by wet sieving method in Horqin area.The content of soil aggregates of>0.25 mm(W_0.25),mean weight diameter（MWD）,geometric mean diameter（GMD）,fractal dimension（D）and soil erosibility factor（K）were studied to explain the distribution and stability characteristics of water-stable aggregates under different cultivation period and soil depth.The soil organic carbon storage of different cultivation years was determined by measuring the organic carbon of aggregates with different particle sizes,and the correlation among the indicators was evaluated.Our main conclusions are as follows:（1）Reclamation exerted remarkable effects on the content of soil water-stable aggregates,the content of macro-aggregates presented an"N"type trend with the increase of cultivation period,which was consistent in different soil layers.（2）W_0.25,MWD and GMD of soil aggregates in 15-20 years were higher than the others,while the D and K were opposite,the stability of the upper layer aggregates was better than that of the lower one.（3）Cultivation promoted the increase of organic carbon content in aggregates,and the organic carbon content of aggregates>1 mm was the highest in 15-20 years of tillage.Reclamation increased the organic carbon storage of macro-aggregates and decreased the organic carbon storage of micro-aggregates.The soil aggregate organic carbon storage of each soil layer under different tillage period was the largest in<0.25mm,and the proportion of organic carbon storage of>1 mm aggregates was the largest in 15-20 years.（4）Correlation analysis showed that soil aggregates content of>1 mm was significantly positively correlated with W_0.25,MWD,GMD and organic carbon content of aggregates（P<0.01）,but was negatively correlated with the aggregates content of 0.5-0.25 mm,<0.25 mm,D and K（P<0.01）,showing that the stability of soil aggregates was closely related to the organic carbon content of aggregates.The higher the organic carbon content of aggregates,the stronger the stability of soil aggregates.In summary,cultivation activities increased the content of soil water-stable macroaggregates,enhanced the stability of soil aggregates,increased the organic carbon content of aggregates and changed the proportion of organic carbon storage in Horqin area.15-20years of cultivation has strong resistance to erosion and carbon sequestration,and cultivation of more than 20 years may lead to land degradation.Conservation tillage,objective fertilization should be considered to increase the proportion of macro-aggregate and the content of soil organic carbon so as to achieve sustainable and healthy development of soil.W_0.25,MWD,GMD,D and K can be used to evaluate the stability of soil aggregates,the water-stable aggregates content of>1 mm can be used as an important parameter to evaluate the soil quality in this area.