Herbage responses and nitrogen agronomic efficiency of bahiagrass–legume mixtures

Abstract

Bahiagrass (Paspalum notatum Flüggé) is the most utilized forage in Florida and requires N fertilization to optimize production. Integrating legumes into bahiagrass pastures may reduce N fertilizer inputs and improve forage nutritive value. This 2-yr, 2-location, on-farm study established two legumes, alfalfa (Medicago sativa L.) or rhizoma peanut (RP; Arachis glabrata Benth.), in mixtures with bahiagrass. We compared bahiagrass-legume mixtures + 45 kg N ha −1 harvest −1 with their non-N fertilized monocultures and with bahiagrass + 90 kg N ha −1 harvest −1 (N-fertilized bahiagrass). Treatments were bahiagrass, N-fertilized bahiagrass, bahiagrass-alfalfa, bahiagrass-RP, alfalfa, and RP. Variables analyzed included herbage accumulation (HA), botanical composition, forage N concentration, forage total N aboveground (TNAG), and N agronomic efficiency. Mixtures and N-fertilized bahiagrass resulted in similar cumulative HA (10,400 kg dry matter [DM] ha −1 yr −1 , on average) and they were greater than all other treatments (4,190 kg DM ha −1 yr −1 , on average). Alfalfa and RP represented low proportions of the mixed swards, with alfalfa proportion being as high as 16.1% and as low as 1.6%. Rhizoma peanut greatest proportion was 2.1% and the lowest was 0.5%. Mixtures and N-fertilized bahiagrass maintained similar N concentrations, but they were consistently lower than legume monocultures. The N-fertilized bahiagrass and mixture treatments resulted in the greatest TNAG in four out of the six sampling dates. The AE N of mixtures was typically greater than N-fertilized bahiagrass. Since legumes had low proportion in mixtures, 45 kg N ha −1 harvest −1 was the upper limit for reaching maximum HA in bahiagrass.

Herbage responses and nitrogen agronomic efficiency of bermudagrass–legume mixtures

“…Santos et al. (2020) reported similar results when alfalfa was growing in association with bahiagrass; nonetheless, the authors reported an even lesser contribution of alfalfa at the beginning of the growing season than that reported in this study. Alfalfa proportion in mixtures with temperate grasses can be as high as 77–99% during the establishment year and remain circa 50% after 3 yr (Aponte et al., 2019).…”

“…In another study performed simultaneously in the same locations, with the same N regimes but utilizing bahiagrass instead of bermudagrass, Santos et al. (2020) reported that total HA of bahiagrass + 90 kg N ha −1 harvest −1 was not different from bahiagrass–alfalfa or bahiagrass–RP receiving 45 kg N ha −1 harvest −1 . Thus, bermudagrass (14,665 kg DM ha −1 yr −1 , on average) response to N fertilization in the present study was apparently greater than observed for bahiagrass (10,600 kg DM ha −1 yr −1 ).…”

“…Therefore, a substantial increase in HA accumulation in conjunction with high N concentration observed for RP in August 2017 resulted in similar total harvested N for this treatment, N‐fertilized bermudagrass, and bermudagrass–legume mixtures. Rhizoma peanut has demonstrated increased total harvested N from April to August, where it usually peaks before the end of the growing season (Santos et al., 2020). Overall, N‐fertilized bermudagrass resulted in greater total harvested N than all other treatments; however, mixtures were often similar to N‐fertilized bermudagrass (Figure 5).…”

“…2015, as described by Santos et al. (2020). Briefly, 20 soil samples were collected at each farm from a 0‐to‐15‐cm depth using a 2‐cm diameter soil probe.…”

“…Plot establishment began in 2015 in an existing well‐established RP hay field (Santos et al., 2020). An already established RP stand was used because it can take up to 2 yr to achieve full establishment of RP when planting a new area.…”