Nitrate Accumulations in Forage Crops1

Abstract The effects of N and P fertilization rates and stage of plant maturity on the nitrate‐N content of nine forage species were studied over a 2‐year period. Species included in the investigations were orchardgrass, tall fescue, bromegrass, bluegrass, timothy, sudangrass, wheat, alfalfa, and ladino clover. Nitrate‐N was determined on hot water extracts of dried plant material by the phenoldisulfonic acid method. Of the species under study, sudangrass accumulated nitrate‐N to the greatest extent. It was closely followed by orchardgrass and fescue. Bromegrass, timothy, and ladino clover accumulated intermediate amounts of nitrate‐N. Alfalfa and wheat accumulated little of this form of nitrogen. Increased N fertilization had a direct effect on nitrate‐N accumulation. Phosphorus fertilization had little if any effect upon the nitrate‐N contents of the various species. Advancing plant maturity was associated with a decline in the nitrate‐N content of most species.