Review: Effects of Biological Nitrogen Fixation and Nutrient Cycling on Stocking Strategies for Cow-Calf and Stocker Programs

Stocking strategies for cow-calf and stocker programs will require different management decisions in response to increasing input costs. With yearlong ownership of cows, costs of fertilization for DM production of pastures and storage of forages are the primary obstacles for positive economic returns. The implementation of legumes into both cool-season and warm-season perennial grass pastures for biological N fixation is intensified by management seeking to reduce input costs. Biological N fixation by the symbiotic forage legume-Rhizobium relationship is dependent on environmental factors as well as the specificity between legume species and Rhizobium strain. The quantity of atmospheric N fixed through forage legume biological N fixation can range as high as 200 kg/ha per year. The seasonality attributes of stocker cattle ownership allow for stocking strategies that may actually intensify short-term fertilizer inputs but use the strategic impact of nutrient cycling to enhance or sustain the perennial grass-based pasture systems. The transfer of N fixed by legumes to companion or follow-up grasses is much less than that of N fixation and is primarily dependent on animal excreta and legume plant decomposition. Stocking rate becomes the primary management strategy of concern that strives to match forage DM production with animal performance expectations and sustainable pastures for economic ventures.