Bahiagrass-Legume Mixtures Reduce the Need for N Fertilizer Inputs in Hay Fields.

Hay production in North Florida is an important economic activity. Bahiagrass is one of the leading forage crops used for hay in Florida, and it requires nitrogen (N) fertilization. Excess of soil N and poor N use efficiency (NUE) may result in N losses to the groundwater where they might become contaminants. Forage legumes fix atmospheric-N₂ and, when growing together with grasses, this N can be transferred and utilized by both. This study assessed the performance of bahiagrass mixed with rhizoma-peanut (RP) or alfalfa in contrast with their monocultures. A randomized complete block design with six treatments and four replicates was performed. Treatments were: 1) bahiagrass monoculture; 2) bahiagrass monoculture + 90 kg N ha^-1 harvest^-1; 3) RP monoculture (Florigraze); 4) alfalfa monoculture (Alfagraze 600 RR); 5) bahiagrass + RP + 45 kg N ha^-1 harvest^-1; and 6) bahiagrass + alfalfa + 45 kg N ha^-1 harvest^-1. Plots measured 3 x 6 m and samples were harvested from 0.5-m² quadrats at 7.5 cm every 5 wks., from March to October 2016. Response variables measured included herbage acumulation (HA), botanical composition (BC), total above ground N, %N derived from atmosphere (%Ndfa), Biological N₂-fixation (BNF), and crude protein (CP). There were treatment, sampling date, and treatment x sampling date effects (P<0.0001) for HA. May, June, and August were the months with the greatest HA. Bahiagrass/Alfalfa, Bahiagrass/RP, and N fertilized Bahiagrass yielded 2007, 1772, and 1873 kg DM ha^-1 haverst^-1 respectively during these three months and did not differ from each other (P>0.05). HA for bahiagrass monoculture, alfalfa, and RP were 1046, 615, and 506 kg ha^-1 harvest^-1 for the same period. Mixing bahiagrass with legumes and adding 45 kg N ha^-1 harvest^-1 yielded as much as fertilizing bahiagrass monoculture with 90 kg N ha^-1 harvest^-1 and created a more sustainable system.