Soil Carbon and Nitrogen Dynamics Under Nellore Cattle and Water Buffalo

Different livestock species can alter soil nutrient dynamics in tropical pastures, but these effects remain poorly documented in seasonally flooded systems. We compared soils under Nellore cattle (Bos indicus) and Mediterranean water buffalo (Bubalus bubalis) in flooded and non-flooded grazing areas of a seasonally flooded, sub-humid tropical pasture in southeastern Mexico. We evaluated total and inorganic pools of surface soil C, N, and P, potential net C (PNCMR) and N mineralization rates (NNM), nitrification (NN), ammonification (NA), exchangeable base cations (Ca, Mg, K, and Na), and physicochemical soil properties (CEC, EA, pH). Effects of livestock species, grazing zone, and their interaction were assessed using linear models with heteroscedasticity-consistent inference, and multivariate patterns were examined using PCA and PERMANOVA. Livestock species seem to affect NH₄⁺, NO₃⁻, PNCMR, C:N ratio, and NNM. Water buffalo soils were associated with higher NH₄⁺, NO₃⁻, and PNCMR, whereas Nellore cattle soils were associated with higher NNM. Grazing zone affected P-Bray, CEC, and exchangeable Ca and Mg, with higher values in flooded areas. Significant livestock × grazing zone interactions were detected for PNCMR, C:N ratio, CEC, Na, Ca, and Mg, suggesting that species effects depend on hydrological context. Overall, our results indicate that livestock species and flooding jointly structure soil biogeochemical functioning in tropical pastures, especially C turnover, inorganic N dynamics, and cation retention.