Dietary Nutritive Value, Dung Quality, Decomposition, and Nutrient Movement into Soil in Smooth Bromegrass Pastures

Abstract

Legumes increase forage nutritive value in pastures; however, literature addressing the impacts on dietary nutritive value, dung quality, decomposition, and nutrient movement into soil remains scarce. Cattle grazing legume‐interseeded smooth bromegrass (Bromus inermis Leyss.) pastures may select diets with greater nutritive value and consequently produce dung that decomposes faster and increases nutrient movement into soil relative to cattle grazing N‐fertilized and unfertilized smooth bromegrass pastures. In 2014 and 2015, we collected rumen and dung samples from replicated experiments to evaluate effects of season (June and August), pasture type (legume‐interseeded, N‐fertilized, and unfertilized pastures), and harvest time (3, 7, and 30 d after deposition) on dietary nutritive value, dung quality, dung decomposition, and nutrient movement into soil. Cattle grazing legume‐interseeded pastures had similar dietary crude protein concentrations but 11% less dietary neutral detergent fiber concentrations than cattle grazing N‐fertilized pastures. Dung from cattle grazing legume‐interseeded pastures, meanwhile, had 5 to 12% greater N concentrations than dung from cattle grazing N‐fertilized and unfertilized pastures. From 3 to 30 d after deposition, dung C/N ratio decreased from 20.0 to 16.5; whereas, dry matter remaining diminished to 77.5%. Dung C/N ratio and dry matter remaining did not vary with season or pasture type. At Day 7, soil below dung from cattle grazing legume‐interseeded pastures had 20 and 42% greater inorganic N than soil below dung from N‐fertilized and unfertilized pastures. This research showed that pastures with legumes increases dietary nutritive value, resulting in greater dung quality and increased N movement into soil.

Vegetation dynamics in nitrogen‐fertilized versus mixed legume‐smooth bromegrass pastures interseeded with sorghum‐sudangrass

“…Belowground transfer of biologically fixed N from legumes to non‐legumes has been described as a principal mechanism for the synergistic effect of legume‐grass mixtures on biomass yields (Frankow‐Lindberg & Dahlin, 2013). Increased nutritive value of cattle diets, return of N‐rich dung, and N movement into soil also has been observed in LEG pastures (Schick et al., 2019) and may have contributed to equivalent perennial grass biomass observed among main plots in our study.…”

Pasture diet of cattle contributes to the reproductive success of dung beetles

“…The rye/clover pasture used in the present study was inter‐sown, and dung from this pasture source had a higher nitrogen content than the improved native‐ and forage oat‐derived dung (Table 2), as expected from previous legume‐based dung studies (e.g., Schick et al, 2019). Increasing grain concentration within feedlot diets increases nitrogen, phosphorus and water‐soluble ammonium (Hao et al, 2009); it can also affect pH and moisture content, which are limiting variables for brood production by dung beetles (Dadour & Cook, 1996).…”

“…The rye/clover pasture used in the present study was inter-sown, and dung from this pasture source had a higher nitrogen content than the improved native-and forage oat-derived dung (Table 2), as expected from previous legume-based dung studies (e.g., Schick et al, 2019).…”

Interseeding annual warm‐season grasses into pastures: Forage nutritive value and yields

“…It produces tremendous growth in spring, particularly with N fertilizer inputs (Guretzky et al., 2013; Snell et al., 2014) but will go dormant in hot, dry summers (Casler & Kallenbach, 2007). Interseeding perennial legumes like alfalfa ( Medicago sativa L.), red clover ( Trifolium pratense L.), and birdsfoot trefoil ( Lotus corniculatus L.) would improve spatial and temporal distribution of forage (Harmoney et al., 2001) and dietary nutritive value (Schick et al., 2019), but dry soil conditions and grass competition often limits their establishment (Groya & Sheaffer, 1981; Guretzky et al., 2004). In this study, we observed that interseeding sorghum–sudangrass or sudangrass offers a strategy to consistently increase CP and IVOMD yields in late‐summer, though a tradeoff would be reduced CP concentrations (Table 6).…”