Impact of grazing on soil properties and cotton yield in an integrated crop–livestock system

The impact of integrating cattle into a sod-based crop rotation was evaluated to understand the short and long-term effects of winter grazing on soil properties and productivity in terms of cotton yield. The rotation consisted of two years of bahiagrass followed by a year each of peanut and cotton. Cattle grazed on oats/rye during the winter. The influence of grazing and irrigation on soil properties such as soil bulk density, organic matter, nitrate N, extractable P, exchangeable K, microbial biomass C, total organic C, and nutrient cycling enzymes (acid and alkaline phosphatases, arylsulfatase, β-glucosidase, and β-glucosaminidase) was examined. Soil bulk density was not significantly affected by grazing at depths lower than 5 cm. The percentage of total organic C that occurred as microbial biomass C at all 3 depth levels (0–5, 5–10, and 10–15 cm) was significantly greater in the grazed plots (1.66–2.07%) than non-grazed plots (0.8–0.85%) when not irrigated. Significantly greater levels of extractable P, exchangeable K and acid and alkaline phosphatases were also observed in the grazed as compared to non-grazed plots indicating efficient nutrient cycling and potential for greater nutrient availability for the following cotton crop. Average cotton lint yield over 4 years (2007–2010) from irrigated grazed and non-grazed plots were 1774 kg ha−1 and 1700 kg ha−1, respectively while the yield from non-irrigated grazed and non-grazed plots was 1613 kg ha−1 and 1376 kg ha−1, respectively. Grazing can have a significant positive impact especially on non-irrigated cotton yield with less fertilizer inputs making a more economical crop while utilizing resources year round.