Mineral-Associated and Particulate Organic Carbon in Coffee Plantations Under Different Production Systems

Regenerative agriculture (RA) is a pivotal management strategy for addressing global warming, characterized by its ability to enhance organic matter (OM) inputs into the soil, leading to increased organic carbon (OC) levels, particularly in its more stable fractions, compared to conventional practices. However, the effectiveness of RA practices is influenced by various factors, including environmental conditions such as temperature and soil moisture, system implementation time, and the diversity of cultivated plant species. This study aimed to evaluate the levels of mineral-associated organic carbon (MAOC) and particulate organic carbon (POC) in two adjacent coffee plots with differing production systems in Patrocínio, Minas Gerais, Brazil. Both plots have been managed for six years, with one employing regenerative practices (RA plot) and the other following a conventional system (CP plot). The RA plot incorporates inter-row cover crops, including millet, sunn hemp, and brachiaria, alongside composting and microbial inoculation, while the CP plot relies on spontaneous weed management between rows. Soil samples were collected at three depths (0-10, 10-20, and 20-30 cm) and subjected to granulometric fractionation using the method described by Cambardella & Elliott (1992). Data analysis was conducted using ANOVA, followed by Tukey’s test (p<0.05) to compare the results. Statistical analyses indicated no significant differences between the two plots for POC and MAOC across all soil depths, suggesting that six years of regenerative practices were insufficient to induce measurable changes in OC accumulation compared to conventional management. Despite this, the results revealed a pattern of higher OC content in the surface layer (0-10 cm) of both plots, with values decreasing at greater depths. This trend reflects the influence of surface vegetation and OM inputs, particularly in the RA plot where cover crops contribute to OM addition. In both plots, MAOC values consistently exceeded POC levels, underscoring the greater stability and persistence of mineral-associated fractions in the soil. These findings suggest that the impact of RA practices on soil OC is a gradual process, requiring longer time frames to achieve significant results, as soil carbon dynamics are complex and influenced by interactions between POC and MAOC. This study highlights the importance of RA practices in promoting carbon sequestration and improving soil health, although their full benefits may take years to materialize. Future research should focus on long-term evaluations and the intricate relationships between carbon fractions to deepen our understanding of RA's potential in sustainable agriculture.