Crop residue addition to the soil promotes an increase in microbial activity and, as a consequence, may improve soil aggregate stability. However, this effect may be different in soils with contrasting aggregation agents. The aim of this study was to evaluate, in an incubation experiment, the role of microbial activity on soil aggregate stability after crop residue addition in two soils with contrasting clay mineralogy. Soybean and maize crop residues were added with three different frequencies on a Mollisol and a Vertisol, which were incubated during a 120-days period. It was studied the dynamics of soil aggregate stability after application of a fast wetting (MWD_fw), slow wetting (MWD_sw) and stirring after prewetting treatment (MWD_st) which evaluates three different breakdown mechanism, i.e., slacking, microcracking and mechanical breakdown, respectively. Microbial activity dynamic was evaluated through measurements of soil respiration rate, microbial biomass-C (MBC) and hot-water extractable carbohydrate-C (HWEC). The Vertisol showed higher resistance to slaking (59% higher) but lower resistance to mechanical breakdown (92% lower) and microcracking (102% lower) than the Mollisol, with a scarce effect of residue quality and addition frequency. The discrete changes recorded in MWD_fw throughout the experiment, were positively associated with changes in cumulative respiration (P < 0.001), MBC (P < 0.05) y HWEC (P < 0.05) in the Mollisol, and only with changes in MBC in the Vertisol (P < 0.05). Also, the small changes in MWD_st were weakly and positively associated (P < 0.05) with changes in cumulative respiration in the Mollisol but not in the Vertisol. However, changes in MWD_sw were closely associated with changes in cumulative soil respiration rate (P < 0.0001) and MBC (P < 0.001) in both soils, and with HWEC only in the Mollisol (P < 0.0001), with a higher effect on these variables than the other aggregate stability test. However, while in the Vertisol the increase in MWD_sw as a function of cumulative soil respiration was lineal, in the Mollisol it was detected an evident increase in MWD_sw up to a threshold of 500 μg C-CO₂ g soil⁻¹ of cumulative soil respiration. Similarly, changes in MWD_sw associated with changes in MBC were higher in the Mollisol than in the Vertisol (i.e. 0.018 v. 0.004 mm of MWD_sw per unit of MBC). Thus, this research added new evidence about the contrasting role of transitory aggregation agents that are provided by microbial activity on aggregate stability in two contrasting soils such as a Mollisol and a Vertisol.

向土壤中添加农作物残渣可促进微生物活性的提高，因此可改善土壤团聚体的稳定性。但是，在使用对比剂的土壤中，这种效果可能有所不同。这项研究的目的是在孵化实验中评估微生物活性对添加土壤残渣的两种土壤形成对比的土壤活性后土壤团聚体稳定性的作用。在Mollisol和Vertisol上以三种不同的频率添加大豆和玉米的农作物残留物，并在120天的时间内进行孵育。研究了快速湿润（MWD _fw），缓慢湿润（MWD _sw）和预湿润处理（MWD _st）搅拌后土壤团聚体稳定性的动态变化。）分别评估了三种不同的击穿机理，即松弛，微裂纹和机械击穿。通过测量土壤呼吸速率，微生物生物量碳（MBC）和热水可提取碳水化合物-C（HWEC）来评估微生物活动动态。与Mollisol相比，Vertisol表现出更高的抗碎裂性（提高59％），但抗机械击穿性（降低92％）和微裂纹（降低102％），对残留物质量和添加频率的影响不大。记录在MWD的离散变化_FW整个实验，均与在累积呼吸的变化相关联（P  <0.001），MBC（P  <0.05）Y HWEC（P <0.05）在Mollisol中，并且仅在Vertisol中MBC发生变化（P  <0.05）。同样，MWD _st的微小变化 与Mollisol中累积呼吸的变化呈弱正相关（P <0.05），而Vertisol中则没有。然而，改变MWD _SW密切与累积土壤呼吸率的变化相关联（P  <0.0001）和MBC（P 只在软土（在土壤<0.001），并用HWEC P  <0.0001），与上一个效果更高这些变量比其他聚合稳定性测试更高。然而，虽然在砂姜黑土中MWD增加_SW由于累积土壤呼吸的函数是线性的，因此在Mollisol中检测到MWD _sw明显增加，直至累积土壤呼吸的阈值为500μgC-CO ₂ g土壤^-1。同样，在Mollisol中，与MBC变化相关的MWD _sw的变化要比在Vertisol中更高（即，每MBC的MWD _sw为0.018 v。0.004 mm ）。因此，这项研究增加了关于瞬时聚集剂的对比作用的新证据，该瞬时聚集剂由微生物活性对两种相反土壤（例如Mollisol和Vertisol）中的聚集体稳定性提供了对比作用。