Herbage Responses to Dogfennel Cover and Limited Nitrogen Fertilization in Bahiagrass Pastures

Abstract

Core Ideas Dogfennel ground cover negatively impacted bahiagrass herbage responses. Bahiagrass provided satisfactory herbage mass in areas with low dogfennel cover in May and June. Limited N fertilization did not change the herbage dynamics of bahiagrass stands competing with varying percentages of dogfennel cover. Further research should be conducted with additional bahiagrass cultivars, soil types, and N fertilizer rates. Nitrogen fertilization is an important management practice in bahiagrass (Paspalum notatum Fluegg) pastures; however, the use of N has been limited in forage‐based livestock systems in Florida. Dogfennel [Eupatorium capillifolium (Lam.) Small] is currently the most common broadleaf weed in bahiagrass pastures. We hypothesize that limited N fertilization might exacerbate dogfennel competition leading to greater declines of bahiagrass herbage responses. Field experiments were conducted in 2007 and 2008 to quantify the effects of dogfennel‐free, low, medium, and high dogfennel cover (0, 1 to ≤25, 26 to 74, and ≥75%) and limited N fertilization (56 kg N ha−1 yr−1) on bahiagrass herbage mass (HM), dogfennel biomass, bahiagrass herbage accumulation (HA) reduction, and bahiagrass crude protein (CP) concentration. Dogfennel biomass was greater for N‐fertilized plots vs. non‐fertilized plots at all monthly evaluations. Bahiagrass HM was satisfactory when dogfennel cover was low early in growing season; however, bahiagrass HM was 29 to 60% and 43 to 71% less in medium and high cover plots, respectively than dogfennel‐free plots. Conversely, bahiagrass CP was negatively affected by dogfennel only when harvested in June and July. Bahiagrass HA reduction increased as dogfennel cover increased in both years. Results from these field trials suggested that dogfennel cover negatively impacted bahiagrass herbage responses, except for low dogfennel cover early in the growing season. Additionally, limited N fertilization did not change the herbage dynamics of bahiagrass stands competing with varying percentages of dogfennel cover. Further research should evaluate additional bahiagrass cultivars, soil types, and N fertilizer rates.