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

Authors: INTERRANTE, S - THE NOBLE FOUNDATION; SOLLENBERGER, L - UNIVERSITY OF FLORIDA; BLOUNT, A - N.FL.RES. AND EDU. CENTER; Coleman, Samuel; WHITE, U - NRCS, WACHULA, FLORIDA; LIU, K - UNIVERSITY OF FLORIDA

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/2009
Publication Date: 11/10/2009
Citation: Interrante, S.M., Sollenberger, L.E., Blount, A.R., Coleman, S.W., White, U.R., Liu, K. 2009. Defoliation Management of Bahiagrass Genotypes: II. Persistence-related Responses. Agronomy Journal. 101:1381-1387.

Interpretive Summary: Bahiagrass is an important grazed forage in the subtropical regions of the USA, particularly Florida and the Gulf Coast. Current ecotypes are day-length sensitive and hence produce very little forage during the winter months. Persistence of a less daylength-sensitive, more cold-tolerant bahiagrass (PCA Cycle 4) was evaluated under a wide range of defoliation practices. Persistence was assessed based on percent cover and rhizome + root and stem base mass, N content, and TNC content in comparison to currently released ecotypes. Argentine cover was unaffected by defoliation treatments, but Tifton 9 and PCA Cycle 4 were much more sensitive to defoliation management. Harvesting every 21 d to an 8-cm stubble height resulted in greatest cover for both Tifton 9 and PCA Cycle 4 (82 and 76%, respectively), while cover for both genotypes was less than 40% if harvested every 7 d to 4 cm. The PCA Cycle 4 genotype often had less root + rhizome and stem base mass, N content, and TNC content than Argentine and Pensacola. These differences were most pronounced when the genotypes were harvested closely or frequently. From these data, it can be concluded that defoliation management of PCA Cycle 4 will likely be more critical than for Pensacola and Argentine bahiagrasses and that Cycle 4 behaves more like Tifton 9 than Argentine or Pensacola. PCA Cycle 4’s upright growth habit, generally less TNC and N in storage organs, and greater reduction in cover with close, frequent defoliation than Argentine and Pensacola imply that management practices such as rotational stocking and greater control of stocking rate are likely to be required for long-term persistence of PCA Cycle 4.

Technical Abstract: Bahiagrass (Paspalum notatum Flügge) cultivars are daylength-sensitive and have minimal cool-season production, resulting in high winter feeding costs in forage-based livestock systems. A new genotype 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 persistence-related responses of photoperiod-sensitive bahiagrasses (diploids ‘Pensacola’ and ‘Tifton 9’ and tetraploids ‘Argentine’ and Tifton 7) and a less photoperiod-sensitive, cold-adapted (PCA) diploid bahiagrass (Cycle 4) to 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 less than 40% cover for both Tifton 9 and Cycle 4. Across defoliation treatments, stem base mass of Pensacola and Argentine was 60% greater than Cycle 4. At 4- and 8-cm stubble height, the advantage was 86 and 41%, respectively. When defoliated every 7 d, Pensacola and Argentine stem 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 non-structural carbohydrate (TNC) content of stem base and root + rhizome fractions. It is concluded that defoliation management of PCA Cycle 4 will be more critical than for Pensacola and Argentine bahiagrasses. More intensive management, i.e., rotational stocking and greater control of stocking rate, is likely to be required to maintain the persistence of PCA Cycle 4.