Nutritive value of fall‐stockpiled tall fescue pastures on southeastern U.S. farms

Abstract

AbstractStockpiling of tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.] may be a useful strategy to avoid fescue toxicosis in autumn and to reduce winter hay feeding costs of beef cattle grazing systems. Typical recommendations are to fertilize with N prior to fall growth. However, little information is available on how soil and pasture conditions affect forage nutritive value responses to fall fertilization. We analyzed the nutritive value of fall‐stockpiled forage in response to N fertilization on 92 fields in North Carolina and neighboring states from 2015 to 2018. We hypothesized that inherent soil nutrient cycling might minimize the need for exogenous N fertilizer inputs. Increasing N fertilization led to (a) greater crude protein, macronutrient concentrations (i.e., K, Ca, and P), and relative feed value and (b) lower acid detergent fiber, neutral detergent fiber, and lignin. However, changes were small, and effects were modified by surface soil properties. For example, crude protein increased from an average of 114 g kg–1 without N fertilization to 131 g kg–1 with 100 kg N ha–1, but this significant N fertilization effect diminished with increasing total organic C and inorganic N of a field. Small changes in nutritive value may have been a consequence of trials conducted on well‐managed farms with relatively high soil‐test biological activity and net N mineralization potential. Therefore, a single recommendation for fall N fertilization may not always be appropriate for enhancing nutritive value. Stockpiled tall fescue had sufficient nutritive value for pregnant cows, and N fertilization may not always be necessary.