Defoliation Management of Bahiagrass Germplasm Affects Cover and Persistence-Related Responses

Bahiagrass (Paspalum notatum Flugge) cultivars are valued for their persistence under grazing and low management inputs. However, they are daylength-sensitive and have minimal cool-season production, resulting in high winter feeding costs in forage-based livestock systems. New germplasm is less daylength-sensitive, possesses greater cold tolerance, and is more productive during the cool season, but its persistence under defoliation is unknown. A field experiment quantified cover and persistence-related responses of photoperiod-sensitive bahiagrass (diploids 'Pensacola' and 'Tifton 9' and tetraploids 'Argentine' and Tifton 7) and a less photoperiod-sensitive, cold-adapted (PCA) diploid bahiagrass (Cycle 4) at two stubble heights (4 and 8 cm) and two harvest frequencies (7 and 21 d). Argentine cover was unaffected by defoliation treatments, but harvesting every 7 d to 4 cm for 3 yr resulted in <40% cover for both Tifton 9 and Cycle 4. Averaging over defoliation treatments, stem base mass of Pensacola and Argentine was 60% greater than Cycle 4. At 4- and 8-cm stubble heights, the advantage was 86 and 41%, respectively. When defoliated every 7 d, Pensacola and Argentine stein base mass was 125% greater than Cycle 4, while the difference was 23% for the 21-d treatment. Similar but less-pronounced responses were observed for N and total nonstructural carbohydrate (TNC) content of stem base and root + rhizome fractions. Defoliation management of PCA Cycle 4 is more critical than for Pensacola and Argentine bahiagrass, and longer regrowth intervals and taller residual heights may be required to ensure its persistence.