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Crop diversification tends to favor the soil fauna community, soil aggregation, and consequently soil organic carbon (SOC) stock. Understanding the association between these attributes can help in understanding the dynamics of physical protection of soil organic matter. In this context, our study aimed to answer: (1) how does the edaphic macrofauna community and soil carbon and aggregate classes respond to two types of coffee agroforestry systems (coffee with Grevillea robusta and coffee with banana) and how these responses differ from native ecosystem; (2) how and to what extent are soil aggregation regulated by the complex structural interactions of plant residue input, SOC, and the soil faunal community? The work was conducted in the municipality of Planalto, state of Bahia, Brazil. Three systems were evaluated: agroforestry system of Coffee arabica L. with Grevillea robusta (CG); agroforestry system of Coffee arabica with Musa spp. (CB); and native forest (NF). Four plots were delimited in each system, in which dry fractionation of the soil was performed to obtain aggregates of classes >6, 6–4, 4–2 and < 2 mm. The macrofauna was sampled using the Tropical Soil Biology and Fertility Program method. The labile and total carbon of the soil and aggregates were determined and the carbon management indices were calculated. The CG and CB presented a greater amount of larger size aggregates (> 6, 6–4 and 4–2 mm) than the NF. The CB system provided more favorable conditions for the soil macrofauna. Despite this, both coffee agroforestry systems favored the occurrence of Oligochaeta. The CG was more favorable to maintain labile fractions of organic matter than the CB. The edaphic fauna show a close relationship with the formation of carbon aggregates and stabilization which was directly influenced by continuous input of plant residues in diverse coffee growing systems. [Display omitted] • The banana coffee system provides favorable conditions for soil macrofauna, aggregation and carbon. • Coffee agroforestry systems (AFSc) favor the occurrence of earthworms and larger aggregates. • The presence of Grevillea robusta in AFSc increases the labile fraction of soil carbon. • The input of residues in AFSc positively influences aggregation and soil carbon stabilization. [ABSTRACT FROM AUTHOR]

ABSTRACT: The conversion of native grassland into farmland causes changes in the soil. Tillage has profound effects on soil organic matter. The intensification of soil tillage decreases soil quality by reducing aggregate stability. Soil aggregate stability and soil organic matter are key indicators for soil quality and environmental sustainability in agro-ecosystems. The aim of the present study is to evaluate the total organic carbon content and the physical and chemical fractions of the organic matter in a soil under different uses and types of management over 27 years. Four soil tillage treatments with two annual crops were evaluated (no-tillage, NT; rotating tillage, RT; minimum tillage, MT; and conventional tillage, CT), as well as bare soil (BS) (standard plot of the Universal Soil Loss Equation - USLE) and natural grassland (NG) as a reference area. The experiment was carried out in an Inceptisol (Cambissolos) in southern Brazil. We determined total organic carbon (TOC) and particulate organic carbon (POC), and organic carbon associated with soil minerals (OCam). The chemical fractionation of carbon was into fulvic and humic acids, and humin. In addition, soil aggregates were divided into five size classes. The type of soil tillage affected the soil organic carbon content, namely TOC, POC, and OCam, as well as the composition of the physical and chemical fractions and their distribution in the arable soil layer. There was a positive relationship between stable aggregates and organic carbon in the soil: the higher the proportion of aggregates in class 1, the higher the organic carbon content. The results support the hypothesis that the carbon stock depends on intensification of a conservation tillage system with a continuous input of C through biomass, which maintains and supplies a continuous flow of C to the carbon transformation processes in the soil.

Indian Black Earths (IBEs) are distributed throughout the Amazon. They are characterized by their high chemical fertility and agricultural potential. IBEs have high organic carbon, favouring the improvement of soil structure. This work aimed to evaluate the aggregates and organic carbon (OC) spatial variability in different IBEs in southern Amazonas. We evaluated the organic carbon spatial variability, mean weight diameter (MWD), soil bulk density (Ïb) and aggregate classes under three uses of soil: pasture, cocoa, and coffee. We collected 528 soil samples in a point grid according to its use at two depths: 0.0-0.05 m and 0.10-0.20 m. Results were subjected to variance, descriptive, and geostatistical analyses. We concluded that the soil use influenced the IBEs physical attributes soil behavior, concentrating the higher values of CO, aggregates > 2.00 mm, and MWD at 0.0-0.05 m in relation to Ïb and aggregates < 2.00 mm where the higher values were the ones at 0.10-0.20 m. Aggregates< 2.00 mm (0.10-0.20 m) and OC (0.0-0.05 m) did not show spatial dependence, while the class of aggregates > 2.00 mm was the only attribute which represented to be a natural characteristic of the soil, with a strong spatial dependence, independently the land use and depth. There was no spatial relationship between the attributes studied and the geomorphic diversity.

Soil mesofauna plays an important role in soil aggregation, which conditions the physical protection of soil organic carbon (SOC). Thus, our study associates the evaluation of mesofauna and SOC quantification to generate relevant information on the influencing level of these organisms on organic matter dynamics in aggregates. It is even more important investigating these indicators in places where decomposition processes are more intense, such as forest systems under tropical soils, where little is known about the interaction between these variables. In this context, the present study aimed to evaluate: (1) the influence of homogeneous Pterogyne nitens and Pinus caribaea plantations on the edaphic mesofauna community and on SOC stocks and carbon in soil aggregate classes using a native forest as a reference; and (2) the interaction between edaphic mesofauna, SOC and aggregate carbon. This study was performed on Oxisol soil areas located in the municipality of Vitória da Conquista, Bahia, Brazil. The edaphic mesofauna was evaluated using the modified Berlese-Tullgren funnel method. Physical soil fractionation was carried out by wet sieving. The organic carbon contents of the soil and aggregates were determined by wet oxidation. Implantation of homogeneous Pterogyne nitens and Pinus caribaea stands causes a reduction in the edaphic mesofauna (abundance and average richness) and in the amount of soil macroaggregates. The differences between the forest systems are largely explained by the abundance of fauna, SOC and carbon of the macroaggregates, microaggregates and silt + clay. The edaphic mesofauna has a direct and positive influence on the SOC, which highlights its important role in regulating the soil carbon dynamics in the soil. [ABSTRACT FROM AUTHOR]