Impact of Three Decades of Conservation Management Systems on Carbon Management Index and Aggregate Stability

Abstract

The sustainability of agroecosystems depends on the maintenance of soil organic matter (SOM) and soil aggregate stability, which are key components of soil health. The long-term effects of conservation management systems, such as the adoption of no till (NT) associated with cover crops, on soil quality are still unclear. The aim of this study was to evaluate the long-term effects of NT systems combined with cropping systems ecologically intensified by the presence of legumes on the carbon management index (CMI) and the state of soil aggregation, as sensitive tools to assess the quality of soil management systems. NT combined with autumn and spring legume cover crops increased the proportion of soil aggregates > 2 mm, resulting in higher weighted average diameters and higher aggregation index values in comparison to conventional tillage (CT), which favored the soil microaggregate proportion. The soil C content was favored by NT only in the surface layer, while the use of legume cover crops increased the C stock by 23% compared to the system without legume cover crops in the 0–20 cm layer. In the topsoil under NT, the stocks of particulate organic matter (POM) and mineral-associated organic matter (MAOM) were 100% and 37% greater than in CT, respectively. A greater CMI was observed under NT compared to CT in systems with no legumes (18%), with one legume (52%), and with two legumes (72%) as cover crops. These results highlight no till’s positive impact on soil health, further enhanced by the legume-based ecological intensification of cropping systems.