Agricultural practices affect the bacterial community structure, but how they determine the response of the bacterial community to drought, is still largely unknown. Conventional cultivated soil, i.e., inorganic fertilization, tillage, crop residue removal and maize (Zea mays L.) monoculture, and traditional organic farmed soil “milpa,” i.e., minimum tillage, rotation of maize, pumpkin (Cucurbita sp.) and beans (Phaseolus vulgaris L.) and organic fertilization were sampled. Both soils from the central highlands of Mexico were characterized and incubated aerobically at 5% field capacity (5%FC) and 100% field capacity (FC) for 45 days, while the C and N mineralization, enzyme activity and the bacterial community structure were monitored. After applying the different agricultural practices 3 years, the organic C content was 1.8-times larger in the milpa than in the conventional cultivated soil, the microbial biomass C 1.3-times, and C and N mineralization 2.0-times (mean for soil incubated at 5%FC and FC). The dehydrogenase, activity was significantly higher in the conventional cultivated soil than in the milpa soil when incubated at 5%FC, but not when incubated at FC. The relative abundance of Gemmatimonadetes was larger in the conventional cultivated soil than in the milpa soil in soil both at 5%FC and FC, while that of Bacteroidetes showed an opposite trend. The relative abundance of other groups, such as Nitrospirae and Proteobacteria, was affected by cultivation technique, but controlled by soil water content. The relative abundance of other groups, e.g., FBP, Gemmatimonadetes and Proteobacteria, was affected by water content, but the effect depended on agricultural practice. For soil incubated at FC, the xenobiotics biodegradation and metabolism related functions were higher in the milpa soil than in the conventional cultivated soil, and carbohydrate metabolism showed an opposite trend. It was found that agricultural practices and soil water content had a strong effect on soil characteristics, C and N mineralization, enzyme activity, and the bacterial community structure and its functionality. Decreases or increases in the relative abundance of bacterial groups when the soil water content decreased, i.e., from FC to 5%FC, was defined often by the cultivation technique, and the larger organic matter content in the milpa soil did not prevent large changes in the bacterial community structure when the soil was dried.

Monitoring of soil organic carbon (SOC) content, SOC pools, and enzymes involved in SOC degradation and mineralization is needed to elucidate the impact of conversion from forest to agriculture on SOC and properties, and how and which crop system and management practices can contribute to C sequestration, thus climate change mitigation. This study compared the impact of forest conversion to maize (Zea mays L.) and cactus (Opuntia ficus-indica [L.] Mill.) fields with different farming management on SOC content and pools (recalcitrant, labile, and extractable), soil microbial biomass carbon, and enzyme activities involved in the soil C cycle. For this purpose, a site under strong land use changes in Central Mexico with high demographic density was selected. Forest conversion to maize fields decreased the original SOC and the C recalcitrance index (RI). However, land use change from forest to cactus systems maintained SOC content, C RI, and arylesterase activity near the values observed in the original forest. Cactus systems promoted higher soil extractable organic carbon content, related to increases in microbial biomass and β-glucosidase activity. Additionally, cactus cultivation can maintain SOC and a C RI at a similar level to the forest soil, which contributes to sustainability of the agroecosystem and climate change mitigation. Therefore, it could comprise a promising viable option for sustainable crop production systems under temperate subhumid conditions, in turn promoting socioeconomic development and rural growth. KEYWORDScarbon recalcitrance index, Opuntia ficus-indica, soil extractable organic carbon, soil organic carbon, sustainability

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Una alternativa para mejorar la fertilidad de los suelos agrícolas en zonas tropicales de México y el mundo es mediante el uso de coberturas vegetales y abonos verdes, principalmente de especies de la familia Leguminosae. El objetivo de este trabajo fue analizar el potencial de las leguminosas como mejoradoras de la fertilidad del suelo en áreas agrícolas tropicales mediante la técnica de investigación documental, considerando investigaciones científicas de los últimos 20 años, período 2000-2023. Derivado de la revisión, se determinaron 14 especies estudiadas ampliamente y 24 más, con alto potencial como mejoradoras de las propiedades físicas, químicas y biológicas de los suelos. Las especies más utilizadas en los trópicos son: Mucuna pruriens L. (DC) (biomasa: 2.6 a 7.9 t ha-1 año-1, N: 80 a 200 kg ha-1 año-1), Canavalia ensiformis (L.) DC (biomasa: 4.6 t ha-1 año-1; N: 173 kg ha-1 año-1) y Centrosema macrocarpum Benth (biomasa: 9.6 t ha-1 año-1, nitrógeno: 311 kg ha-1 año-1). La producción en los cultivos asociados con leguminosas ha aumentado hasta en 50%. A pesar de los beneficios al suelo y en la producción, la aceptación y adopción de leguminosas ha sido limitado por diferentes causas, entre ellas: la falta de percepción de los beneficios de las leguminosas, fallas en la tecnología generada y aplicada, y escaso enfoque participativo en su selección. Con la información generada en este trabajo se concibieron 10 recomendaciones para facilitar la selección de especies, proveer información que faciliten su adopción y que sirva como base en futuras investigaciones.