Bromus inermis forage production and quality under long-term rotational grazing and nutrient enrichment in Eastern Nebraska, U.S.

Rising food and feed demand, coupled with climate uncertainties, poses a growing threat to the sustainability and resilience of pasture and agriculture lands in the Great Plains. Smooth bromegrass ( Bromus inermis, Lyess ), a C 3 cool-season grass, dominates cattle grazing pastures in eastern Nebraska and is valued for its productivity and nutritional quality. However, nitrogen fertilization of smooth brome pastures carries nitrate leaching risks, and potential water degradation. Dry Distiller Grains plus Solubles (DDGS), a by-product of corn ethanol production, has emerged as an alternative to mineral fertilization. This study investigated the interactive effects of long-term (2005–2023) pasture management (fertilization and rotational grazing) and climate variability on smooth bromegrass performance over four years (2020–2023). Treatments included mineral nitrogen fertilization, DDGS supplementation, and no fertilization, each under grazed and ungrazed conditions. Biomass (total and live), leaf area index, chlorophyll content, crude protein, acid detergent fiber, neutral detergent fiber, and soil moisture were measured seasonally and across years. Results showed that fertilization consistently produced higher biomass, leaf area index, and crude protein, relative to other treatments, reinforcing its role in sustaining forage productivity. DDGS, while offering a reduced environmental footprint, showed potential in enhancing forage production and quality under average or above average precipitation and soil moisture. However, its efficacy declined during dry years. While long-term fertilization treatment remained the most consistent strategy for sustaining productivity under both ungrazed and rotational grazing systems, DDGS supplementation emerged as a strategic option for regions with adequate growing season precipitation, reducing reliance on mineral fertilizers without compromising yields. These findings emphasize the value of adaptive practices that integrate fertilization and grazing to maintain smooth bromegrass productivity under increasing climate variability. • Mineral fertilization of bromegrass showed the highest forage quality and quantity. • Dry Distiller Grains plus Solubles supplementation is comparable to mineral fertilization. • Rotational grazing enhanced forage quality, complementing fertilization strategies.