Impacts of Three Nitrogen Fertilizer Levels on Growth Rates of Grasses and Legumes, and Nodulation Rates of Legumes


  • Kortni Ferraro
  • Katherine R McNees
  • Casi Swain


Three nitrogen fertilizer rates (18, 68, and 118 lb/ac of N) were applied to small research plots that had been sprayed previously for weeds and tilled at the Oakley Farm in Livingston, TN. Forage plots were planted to six different grasses (Creeping Red Fescue/ Festuca rubra, Kentucky Bluegrass/ Poa pratensis, “Marshall” Ryegrass/ Lolium multiflorum, Timothy/ Phleum pratense, “Kentucky 31” Tall Fescue/ Festuca arundinacea, and Orchardgrass/ Dactylis glomerata) and five different legumes (Crimson Clover/ Trifolium incarnatum, “Will” Ladino Clover/ Trifolium repens, “Kenland” Red Clover/ Trifolium pratense, common Red Clover/ Trifolium pratense , White Clover/ Trifolium repens). All plots also received the equivalent of 50 lb/ac P2O5 and 50 lb/ac K2O prior to planting. Grasses typically have a graded response to N fertilizer levels, increasing growth rates as nitrogen is increased. Closer evaluation of the legumes which can “fix” their own nitrogen, to determine if additional nitrogen fertilizer is applied, how it will impact legume growth rates and root nodulation. It has been reported legumes become “lazy” and use the applied nitrogen fertilizer and not nodulate and fix their own nitrogen. Plots will be evaluated every two weeks for germination and percent ground cover, and also for plant heights and estimated dry matter yield. Further, the five legume plots will have individual plants harvested, including the roots, and carefully washed, to count root nodulation in the five legume varieties to evaluate the impacts of nitrogen fertilizer on nodulation amounts for each legume under each nitrogen fertility treatment.