Forage, carbon accumulation, and soil physical characteristics in a crop–livestock production system

Abstract

Crop-livestock systems may improve land use and food security; however, heavy grazing can impair the soil physical properties and reduce the forage accumulation of subsequent crops. The study was conducted to evaluate the impact of mechanically harvest or low-intensity grazing on the physical properties of soil and the productivity of an annual pasture, ryegrass (Lolium multiflorum L.), and its successive crop, maize (Zea mays L.). Pasture and maize were evaluated from 2017 to 2021 and 2021 to 2022, respectively. The ryegrass was either mechanically harvested for silage production or grazed when the pre-defoliation sward height was between 20 and 25 cm. The total forage accumulation increased (P < 0.08) by approximately 500 kg ha⁻¹ and forage accumulation rate were 25% greater (P < 0.01) in grazed pastures than in non-grazed pastures. Different pasture defoliation methods did not affect the physical properties of the soil. The total organic carbon concentration tended to be greater (P = 0.058) in the grazed area than in the non-grazed area, and the maize forage accumulation (average = 14,611 kg ha⁻¹) and chemical composition were similar for plants from the previously grazed and non-grazed areas. Four consecutive years of grazing did not impair the physical quality of the soil and DM production in either the pasture or maize silage. Thus, moderate grazing can be sustainably implemented over multiple years without degrading soil structure or reducing the productivity of forage and subsequent crops.