Reducing N Fertilizer Inputs in Stocker Systems By Adding Forage Legumes.

Legumes add N to the system and often present greater nutritive value. We evaluated potential benefits of including cool-season legumes in livestock-forage systems in North Florida. The experiment was conducted from January to May, 2016 at the University of Florida, North Florida Research and Education Center. Three treatments were evaluated: 1) fertilized bahiagrass pastures overseeded with a mixture (56 kg ha-1 of each) of FL 401 cereal rye (Secale cereale, L.) and RAM oat (Avena sativa, L.) and fertilized with 112 kg N per ha; 2) perennial peanut/bahiagrass pastures overseeded with similar rye/oat mixture fertilized with 34 kg N ha-1 plus a mixture of clovers (17 kg ha-1 of Dixie crimson, 6.7 kg ha-1 of Southern Belle red, and 3.3 kg ha-1 of Ball clover); 3) unfertilized bahiagrass pastures overseeded with similar grass/clover mixture + 34 kg N ha-1. Treatments were replicated in three blocks in a randomized complete block design. Pastures were continuously stocked using a variable stocking rate. A treatment × evaluation period interaction (P < 0.001) was observed for ADG, stocking rate (SR), gain per area (GPA), and herbage mass. Interaction occurred because the fertilized grass peaked earlier in the season compared to grass/clover mixtures, affecting all these responses. Total season average for ADG and SR were 0.8 kg head-1 d-1 and 3.7 steers ha-1, respectively. Gain per area in the season averaged 412 kg BW ha-1. No treatment or treatment × evaluation period interaction (P > 0.05) was observed for herbage allowance, averaging 0.83 kg of DM/kg of cattle live weight. Livestock performance differed along the season because of different timing among treatments, but total season performance was similar. Therefore, it is possible to maintain livestock production with reduced N fertilization by adding cool-season legumes. Keywords: Clover, N fertilizer, beef cattle.