Grazing intensity determines pasture spatial heterogeneity and productivity in an integrated crop-livestock system

Abstract

Spatial heterogeneity is a property of natural ecosystems. Integrated crop-livestock systems (ICLS) aim to mimic natural ecosystem functions as pillars of sustainable intensification, and grazing is a process that potentially affects spatial heterogeneity. Then, we investigated the effect of different grazing intensities, defined according to a range of sward heights (intensive grazing, 10 cm; moderate grazing, 20 cm; moderate-light grazing, 30 cm; light grazing, 40 cm; and ungrazed), on the spatial heterogeneity and biomass productivity of mixed Italian ryegrass (Lolium multiflorum Lam.) and black oat (Avena strigosa Schreb.) pastures. The mixture was grazed by steers under continuous variable stocking, using put-and-take animals to maintain targeted sward heights. The pasture was in rotation with soybean in an integrated crop-livestock system for 15 years. Data concerns pasture phase on the 15th rotation cycle. Cattle grazing at moderate to light intensities increased pasture spatial heterogeneity and total aboveground primary productivity, while intensive grazing led to homogeneous overgrazed canopies with frequent bare soil patches. Pre-grazing sward structure suggests that the summer crop rotation buffers the contrasts created by grazing at different intensities. This study suggests that moderate to light grazing intensities increase pasture productive efficiency and create more heterogeneous canopies in ICLS, while intensive grazing should be avoided.