Perennial warm-season grass monocultures and mixtures: Biomass production and soil improvement in semiarid and shallow soil conditions

Perennial warm-season grasses (WSG) represent a viable alternative for cultivation in marginal lands. Moreover, mixtures of WSG can be expected to exceed monocultures in terms of biomass production since biodiversity and ecosystem functions are predominantly positively related. Our objective was to evaluate (1) stockpiled forage accumulation and quality and (2) root biomass in monocultures and mixtures of Panicum virgatum, P. coloratum and Eragrostis superba, and to compare them with a standard monoculture of E. curvula. Additionally, the soil properties under WSG pastures and annual forage crops were compared at the end of the study. The research was conducted in the Dry Pampas of central Argentina, under shallow soil conditions. Stockpiled forage accumulation and root biomass were higher in the most diverse pasture and the mixture of P. virgatum - E. superba than in the monoculture of E. curvula. Stockpiled forage represented an important source of feed for livestock in fall and winter, although of low quality. Soil aggregate stability and initial water infiltration rate were higher in WSG pastures than in adjacent annual forage cropland. Our results suggest that mixtures of WSG can be highly productive in semiarid environments even in shallow soils. Moreover, they can positively influence soil properties.