El karst del estado de Yucatán, México, tiene su origen en los arrecifes coralinos y sedimentos marinos que, al exponerse a la superficie, formaron la roca caliza. Los procesos de solubilización-precipitación de esta roca han promovido la ausencia de corrientes de agua superficiales, un relieve ligeramente ondulado con planicies, depresiones y montículos, afloramientos y presencia de cenotes. Los diferentes grados de porosidad y dureza de la roca han permitido la formación desde pequeñas oquedades y acumulaciones de suelo, hasta complejos sistemas de cuevas secas y húmedas. El manejo de este tipo de áreas debe partir del conocimiento de su origen, morfología y biología para garantizar el uso sustentable de los recursos naturales. Se requiere especial atención en el manejo de la extracción de roca caliza, las actividades turísticas y productivas relacionadas con el uso de agua del acuífero, así como el volumen y calidad de las descargas de aguas residuales al suelo, cenotes y el mar.

Decomposition and N release pattern from the leaves of three shrubs species were studied under field conditions. Leaves of Leucaena leucocephala (Lam.), Guazuma ulmifolia (Lam.) and Moringa oleifera (Lam.) and two mixtures, Leucaena + Moringa and Leucaena + Guazuma, in a complete randomized block design, were studied during the dry and wet seasons. Litterbags were randomly distributed in each experimental block and placed on the soil surface, and residues were recovered after 2, 4, 8, and 16 weeks. Double exponential model decay was better fitted to describe the pattern of the decay of the release of various leaf constituents. Litter dry weight loss and N release were faster from Moringa, followed by the Leucaena + Moringa mixture, while the Guazuma leaf litter decomposed much slower. In the wet period, a rapid N release was observed for Moringa (60%) and Leucaena + Moringa (43%) in the first two weeks. In contrast, Guazuma and the Leucaena + Guazuma mixture released about 46% of N in 16 weeks. In the dry period, leaves released most of their N during the first 8 to 16 weeks. Moringa and Leucaena + Moringa ranked first, having lost 81 and 75% of its initial N, respectively. The ratios of condensed tannin and polyphenols to N were significantly correlated with the N released. It was concluded that the initial mass loss from the leaf litter was high and rapid in the rainy period in comparison to the dry period. The residue disappearance pattern of Moringa, Leucaena and Leucaena + Moringa followed an asymptotic model, with more than 80% of the original residue released during the 16-week study period.

Glyphosate is the most widely used herbicide worldwide and in Mexico; however, its effects on soil microbiota in traditional agroecosystems remain unclear. We evaluated bacterial, archaeal, and fungal responses to commercial glyphosate in three representative karst soils of the Yucatán Peninsula (black Leptosol, red Leptosol, and red Cambisol) historically associated with the Mayan milpa system. The high-throughput sequencing of the 16S rRNA V4 and ITS1 regions was used to assess diversity patterns and differential abundance. Glyphosate application did not significantly alter alpha or beta diversity; however, fifteen taxa classified at the genus level exhibited shifts in relative abundance. Most bacterial taxa were depauperated in treated soils, whereas others, such as Arthrobacter, were enriched after application, indicating the presence of tolerant or resistant bacteria that may play a role in glyphosate degradation. Cordyceps, an entomopathogenic fungus, was depleted, indicating potential for natural pest control. The similarity of the core microbiota between samples with and without glyphosate application indicates that these communities are resilient. Overall, under short-term exposure, glyphosate induced compositional shifts in specific taxa without major effects on community structure but with potential implications for soil functionality and resilience in the Mayan milpa.

Objective: To evaluate the effect of native rhizobial strains on nodulation, growth, dry biomass production, total nitrogen (N) and carbon (C) content in plant tissue, as well as nitrogenase activity in seedlings of Leucaena leucocephala. Design/Methodology/Approach: The study followed a completely randomized design. Seeds of L. leucocephala were germinated in an inert substrate, and six treatments were evaluated, corresponding to native rhizobial strains and an uninoculated control. Plants were harvested at 45, 75, and 105 days, and the following parameters were measured: (i) total number of nodules, (ii) plant height (root and shoot), (iii) dry plant weight, (iv) carbon and nitrogen content in dry biomass, and (v) nitrogenase enzyme activity. Results: Treatments with strains 40, 41-2, and 46 showed the highest number of nodules at 75 days. At 105 days, plants inoculated with strain 74 had a significantly higher average dry biomass (p < 0.001). The average nitrogen content was significantly higher (p < 0.0001) in treatments with strains 26, 34b, 46, and in control. No significant differences were observed in carbon content among treatments. Nitrogenase activity was confirmed in all inoculated treatments but was absent in control. Limitations/Implications: The results obtained with native Rhizobium sp. strains highlight their potential to enhance biological nitrogen fixation in Leucaena leucocephala, which could contribute to the development of more sustainable agroforestry systems, especially in nitrogen-deficient soils. Findings/Conclusions: This study highlights the potential of certain native rhizobial strains for inoculating L. leucocephala, enhancing its growth and development. However, further research under field conditions is needed to confirm these findings.