Forage production and persistence characteristics of grazed native warm-season grass mixtures with or without nitrogen fertilizer

Background

Native warm-season grass (NWSG) mixtures may provide a low-nitrogen (N)-input summer perennial forage option to extensively managed forage–livestock systems.

Methods

Mixed pastures of big bluestem (Andropogon gerardii Vitman), little bluestem (Schizachyrium scoparium Michx.), and indiangrass (Sorghastrum nutans L.) fertilized with 0 or 67 kg N ha⁻¹ were continuously stocked with beef heifers and cows. Forage mass, nutritive value, and canopy heights were determined every 2 weeks during the grazing season. Stand persistence measures included the canopy cover and leaf area index (LAI) and plant crown density at spring emergence following 3 years of grazing management.

Results

Forage mass, canopy height, and stocking densities were greater for N-fertilized NWSG than unfertilized NWSG for the first 30 days of the growing season across the 3-year study. Forage NWSG fertilized with N had a greater decrease in LAI during the growing season (51% decrease) than unfertilized NWSG. Spring NWSG plant density estimates following 3 years of grazing did not differ across N management strategies.

Conclusions

Forage NWSG mixtures supported superior forage attributes and greater stocking densities early in the grazing season under low-level N than zero-N-input systems and may provide a low-N-input alternative for improved species use in southeastern US forage–livestock systems.