Effects Of Tillage And Organic Materials Application On Soil Carbon Pool And Soil Aggregate Stabilization

In this study, the stabilization of soil aggregates and soil organic carbon (SOC) pool of six soils, from Yunnan and Guandong, with different land use and different soil managements were analyzed, and some factors influencing the stabilization of soil aggregates were quantified and discussed. The role of labile soil organic carbon in the stabilization of soil aggregates and the evaluation of soil quality was also discussed. In addition, the soil stratification ratio was compared in the six soils.The main results were obtained as follows:1 . There were significant positive correlations between the mass percentage of the greater aggregate size fractions (10-5 mm, 5-2 mm) and the different soil organic carbon pools, and between the amounts of organic carbon in these fractions and the different organic carbon pools of the whole soil.2. The significantly correlations between soil hot-water extractable organic carbon (HWOC), as the major part of the labile soil organic carbon, and the MBC and its activity, the mineralized rate ofSOC and SOC (n = 56, p< 0. 001).3 . Soil carbon management index (CMI) sensitively reflected the dynamics changes of SOC pool under with different land use and different soil managements.4. Path analysis showed that HWOC, which was continuously produced by soil microbe through organic matter transformation was the key factor for the stabilization of soil aggregates while soil texture and pH had only minor importance.5 . The aggregate size distribution of surface soil was influenced greatly by tillage, especially, the proportion of the > 2 mm aggregate size fraction changed more than others.Higher stratification ratio of soil aggregate geometric mean diameter (GMD) generally meaned that smaller soil disturbance, but this ratio of grass soil may be lower in the case of roots spread along the soil profile.In brief, HWOC, CMI and stratification ratio of soil aggregate GMD, whose changes were sensitive to disturbances on soil, can reflect the situation of soil nutrient and the feature of soil properties.Thus, they may be good indicators of assessing soil qualities.