Soil aggregation and associated organic matter under management systems in sandy-textured soils, subtropical region of Brazil

Abstract

Abstract Increasing the diversity of plant species in agricultural production areas favors the maintenance or improvement of soil quality, particularly for soils with a sandy texture. This beneficial effect is related to the formation of aggregates of different origins. This study aimed to i) verify whether soil use and management affect the proportion of biogenic (Bio) and physicogenic (Phy) aggregates, and ii) verify whether biogenic aggregation is more likely to lead to soil improvement than physicogenic aggregation. Three management systems were evaluated (permanent pasture, PP; no-tillage system, NT; and no-tillage + Brachiaria system, NT + B) as well as a reference area (Atlantic Forest biome vegetation, NF). According to their origin or formation pathway, the aggregates were separated, identified, and classified as Bio (formed by biological processes) and Phy (resulting from chemical and physical actions). Only the PP area promoted greater aggregate formation through Bio. The PP area also increased the total organic carbon (TOC) content of the aggregates and affected the isotopic signal of δ13C. The NT + B system provided an increase in the TOC content of its aggregates in comparison with aggregates in the NT and NF areas. Among the formation pathways, the Bio aggregates had the highest TOC and SOM fractions contents and the most negative δ13C values. The higher amounts of plant residues in the soil was more important than the diversity of species in favoring the formation of Bio aggregates. The beneficial effect of Brachiaria can also be observed when adopted in consortium with corn in grain production systems.