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ABSTRACT
Annual ryegrass (Lolium multiflorum Lam.) provides livestock feed and captures nutrients from fields receiving manure application. The objective of this study was to determine relationships among maturity and yield, mineral uptake, and mineral concentration. Primary spring growth of ‘Marshall’ ryegrass was harvested every 7 d to 56 d maturity and was fertilized with swine effluent containing 254 and 161 kg nitrogen (N) and 42 and 26 kg phosphorus (P) ha−1 for two years. Yield increased linearly to a maximum of 13.6 mg ha−1 after 49 d in 2001 and 8.0 mg ha−1 after 56 d in 2002. Mineral uptake was highly correlated (r > 0.95) with yield and attained a maximum single harvest of 192 kg N ha−1 and 32 kg P ha−1 (mean of two years). Concentration of all minerals except calcium (Ca) declined as ryegrass matured. Low magnesium (Mg) concentration (< 2 g kg−1 dry matter) increases the risk of hypomagnesemic grass tetany.
