CONICET | Buscador de Institutos y Recursos Humanos

The inclusion of tropical grass forage as a cover crop (CC) could be a useful tool to improve microbiologicalactivity and, consequently, soil quality. The aim of this study was to evaluate the effect of Brachiaria brizantha cv.Mulato and maize (Zea mays) as CC on soil microbial communities and their contributions to a degradedcommon bean (Phaseolus vulgaris L.). monoculture system. Soil sampling was carried out in 2016 after six yearsof cumulative effect across different treatments: B. brizantha-B. brizantha-common bean (B2), B. brizanthacommonbean (B1), maize-common bean (M) and common bean monoculture (control). B2 and B1 showedhigher fluorescein diacetate hydrolysis (108.1% and 78.6%, respectively) and higher acid phosphatase activity(304.5% and 181.6%, respectively) compared with the control treatment. The metabolic efficiency was higher intreatments containing B. brizantha as CC, with a significantly lower metabolic quotient (respiration rate per unitmicrobial biomass carbon) in B2 (1.65) compared with the control (5.46). The B2 treatment also showed highervalues of soil organic carbon, which was correlated with soil microbial activities. In contrast, qPCR analysis ofmicrobial structure did not show significant differences in response to the evaluated treatments. Thus, fungal andbacterial abundance probably had less influence on the differentiation of treatments compared to microbialactivity and soil chemical properties. In context of this research, the use of B. brizantha as CC increased soilfertility and generated a greater microbial metabolic efficiency. Our research demonstrates that B. brizantha cv.Mulato as CC is a suitable agricultural tool to restore soil biochemical properties.

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