Short-Term Impacts of No Tillage on Aggregate-Associated C in Black Soil of Northeast China

In order to get a good indicator to evaluate the impacts of no tillage (NT) on soil structure and soil quality, we studied the dynamics of total soil organic carbon (SOC) and aggregate-associated SOC, and their relationships in the plow layer (30 cm) in black soil of Northeast China under NT practice. The tillage experiment was established in Dehui County, Jilin Province, China, in 2001. The total SOC and aggregate-associated SOC under 5-yr tillage treatments were measured. NT practices did not lead to the increase of average SOC content at 0-30 cm depth, but it did significantly increase SOC at the top soil (0-5 cm). In NT plots, the change of SOC in >1 000 mu m aggregate was the same with that of total SOC, but the effect of NT on SOC in >1 000 mu m aggregate was greater than the effect on total SOC, suggesting that >1 000 mu m aggregate had more sensitive response to the impact of tillage practices. Also, significant positive correlation occurred between total SOC and SOC in >1 000 mu m aggregate in black soil. Consequently, in the short term soil macroaggregate >1 000 mu m could be used as an indicator to evaluate the impacts of tillage practices on soil structure in black soil of Northeast China.