Submitted to: Journal of Plant Nutrition
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/9/2005
Publication Date: 6/1/2006
Citation: Brink, G.E., Sistani, K.R., Oldham, J.L., Pederson, G.A. 2006. Maturity effects on mineral concentration and uptake in annual ryegrass. Journal of Plant Nutrition. 29:1143-1155. Interpretive Summary: When planted in a warm-season grass pasture, cool-season annual ryegrass forage provides additional livestock feed and removes nutrients from soils receiving manure when harvested as hay. We conducted this study to determine how the maturity of ryegrass is related to its yield, uptake of nutrients, and nutrient concentration of the forage. Liquid swine manure was applied to ryegrass during the spring. Initial grass growth was harvested every 7 days for 56 days. We found that nutrient uptake was maximized by allowing ryegrass to reach full maturity. At late growth stages however, the nutritional value of ryegrass forage declined to levels below that which may be required for adequate nutrition of livestock. The concentration of one mineral, magnesium, was low enough to increase the potential for nutrient imbalances in ruminant livestock.
Technical Abstract: When sown into a perennial warm-season grass, annual ryegrass (Lolium multiflorum Lam.) provides additional livestock feed and a means of capturing nutrients from fields receiving manure application. Our objective was to determine relationships among maturity and yield, nutrient concentration, and nutrient uptake in annual ryegrass. The study was conducted on a Prentiss loam (coarse-loamy, siliceous, semiactive, thermic Glossic Fragiudult) soil. 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 N and 42 and 26 kg P ha-1 in 2001 and 2002, respectively. 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. Nitrogen and P uptake were highly correlated (r > 0.95) with yield and attained maximum single-harvest of 192 kg N ha-1 and 32 kg P ha-1 (mean of 2 yr). With the exception of Ca, concentration of all minerals declined as ryegrass matured from 7 to 56 days of growth. Of potential concern to livestock producers, the low Mg concentration measured in ryegrass (< 2 g kg-1 dry matter) throughout primary spring growth poses an increased risk of hypomagnesemic grass tetany, particularly at early growth stages.