Strip-planting of rhizoma peanut in bahiagrass pastures to increase production and sustainability of low-input forage-livestock systems in Florida.

摘要

Rhizoma peanut (Arachis glabrata Benth.; RP) is a subtropical legume with potential to be grown in association with grasses like bahiagrass (Paspalum notatum Flugge) to increase/maintain productivity and sustainability of extensive low-input forage-livestock systems of the southeastern USA. In this work, four studies were conducted in Florida to investigate the viability of planting 'Florigraze' RP in strips into existing bahiagrass pastures. Using this approach, the specific objectives were to evaluate: 1) defoliation options during the year-of- and year-after establishment, 2) weed management, 3) N fertilizer application to establishing RP, and 4) seedbed preparation effects on RP establishment success. The results indicate that a single application of the herbicide glyphosate to kill bahiagrass followed by mowing the above-ground biomass to 5-cm stubble height before planting RP provides adequate seedbed for RP establishment and may reduce costs compared to conventional practices that include several passes of heavy equipment to plant RP in a fully prepared seedbed. Regardless of method of seedbed preparation in the strip, it should be followed by a single application of herbicides imazapic (0.07 kg a.i. ha-1) or imazapic + 2,4-D amine (0.07 and 0.28 kg a.i. ha-1, respectively) when broadleaf and grass weeds reach 5- to 10-cm height to provide extended control of weeds. Light environment at the RP canopy height was ≥ 96% of the incident photosynthetically active radiation (PAR) when imazapic and imazapic + 2,4-D amine herbicides were used compared to ≤ 82% for the other treatments. The use of imazapic stunts bahiagrass growth temporarily providing time for RP establishment. Thus, it is the end of the season until bahiagrass actively regrows, resulting in a bahiagrass-RP mixture in the strips. Greatest RP canopy cover and frequency during the establishment year were ∼35 and 80%, respectively, and occurred in plots where imazapic and imazapic + 2,4-D amine were applied. Application of 50 kg N ha-1 following herbicide application of imazapic or imazapic + 2,4-D amine increased RP canopy cover (+10 percentage points) and frequency (+15 percentage points) in plots where weeds had been controlled successfully. Measurements indicated that early in stand life RP spread at a rate of ∼36 cm yr-1 into the adjacent bahiagrass sward. During the year of establishment, utilization of the establishing RP should be hay production to prevent loss of RP plants in the strip under grazing due to animal preference for plants in the strip and resultant overgrazing. During the year after establishment, grazing management strategies should be targeted to favor the RP in the strip, i.e. maintaining at least a15-cm stubble in the planted strip regardless of the height of the adjacent bahiagrass. Based on these results it is concluded that strip planting of RP is an option for incorporating the legume into grass-based pastures, but critical management factors for establishment success include avoiding excessive defoliation by grazing during the first 2 yr of stand development and controlling competition to RP in the strip by use of herbicides.