Effects of nitrogen fertilization on soil nutrient concentration and phosphatase activity and forage nutrient uptake from a grazed pasture system

• Published in: Journal of environmental management 2015-05, Vol.154, p.208-215
• Main Authors: Dillard, Sandra Leanne, Wood, Charles Wesley, Wood, Brenda Hall, Feng, Yucheng, Owsley, Walter Frank, Muntifering, Russell Brian
• Format: Article
• Language: English
• Subjects: Animal Feed - analysis; Animal Husbandry; Animals; Beef cattle; Biomass; Cattle; Conductivity; Cynodon - metabolism; Cynodon dactylon; Edible Grain - metabolism; Effects; Female; Fertilization; Fertilizers; Festuca - metabolism; Forage; Forages; Lolium; Male; Medicago - metabolism; Nitrogen; Nutrients; Pastures; Phosphoric Monoester Hydrolases - metabolism; Phosphorus; Poaceae - metabolism; Recommendations; Seasons; Soil (material); Soil - chemistry; Soils; Trifolium - metabolism; Trifolium incarnatum; Triticale; Uptakes; Vigna unguiculata
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2015.02.035

Over a 3-year period, the effect of differing N-application regimes on soil extractable-P concentration, soil phosphatase activity, and forage P uptake in a P-enriched grazed-pasture system was investigated. In the fall of each year, six 0.28-ha plots were overseeded with triticale ( × Triticosecale rimpaui Wittm.) and crimson clover (Trifolium incarnatum) into a tall fescue (Lolium arundinacea)/bermudagrass (Cynodon dactylon) sod and assigned to 1 of 3 N-fertilizer treatments (n = 2): 100% of N recommendation in a split application (100N), 50% in a single application (50N), and 0% of N recommendation (0N) for triticale. Cattle commenced grazing the following spring and grazed until May. In the summer, plots were overseeded with cowpea (Vigna unguiculata), fertilized at the same rates by reference to N recommendations for bermudagrass, and grazed by cattle until September. There were no effects of N fertilization on soil phosphatase activity, electrical conductivity, or concentrations of water-soluble P. Concentrations of extractable P decreased in plots receiving 50N, but increasing N fertilization to 100N resulted in no further reduction in extractable P. Forage biomass, foliar P concentrations, and forage P mass were not affected by N fertilization rates at the plant-community level, but responses were observed within individual forage species. Results are interpreted to mean that N fertilization at 50% of the agronomic recommendation for the grass component can increase forage P mass of specific forages and decrease soil extractable P, thus providing opportunity for decreasing P losses from grazed pasture. •Changes in P concentration of soil and forage of a grazed pasture system was determined.•Soil extractable P decreased with greater N-fertilization.•Neither foliar P nor forage P mass were affected by N-fertilization regime.