Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/17/2009
Publication Date: 8/9/2009
Citation: Interrante, S.M., Sollenberger, L.E., Blount, A.R., White, U.R., Liu, K., Coleman, S.W. 2009. Defoliation Management of Bahiagrass Germplasm Affects Dry Matter Yeild and Herbage Nutritive Value. Agronomy Journal. Volume 101, Issue 4. 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. A new bahiagrass ecotype (PCA Cycle 4) that is a less daylength-sensitive and more cold-tolerant was evaluated under a wide range of defoliation practices. Yield and forage nutritive value was assessed beginning in May over 3-yr in comparison to currently released ecotypes. During 3 yr of defoliation by clipping, PCA Cycle 4 yielded similarly or slightly less than the diploid cultivars Pensacola and Tifton 9. In most cases, the tetraploids Argentine and Tifton 7 outyielded PCA Cycle 4. Defoliation management influenced ranking of genotypes. Yield of PCA Cycle 4 was less than all other genotypes when harvested every 7 d, but it was similar to that of the other diploids when harvested every 21 d. Through May 2005 and mid-June 2006 and 2007, the diploids, including PCA Cycle 4, outyielded the tetraploids, but the tetraploids generally yielded more than the diploids for the remainder of the growing season. The lesser spring yields of the tetraploids are consistent with previous reports of slower early-season growth (Chambliss and Adjei, 2006). The PCA Cycle 4 genotype generally had similar total-season and within-season CP concentrations as the other diploids, while Argentine often had the greatest herbage CP concentrations among genotypes during summer. The PCA Cycle 4 genotype had IVDOM that was similar to or greater than the other diploids and generally greater than the tetraploids, suggesting potential for modestly greater animal performance than some current cultivars. From these data, it can be concluded that PCA Cycle 4 is no more productive during the May through October grazing season than other current cultivars of bahiagrass. Relative to the other cultivars, it is considerably less productive when harvested frequently (7 d), perhaps suggesting that its upright growth habit makes it less tolerant of frequent defoliation. Herbage CP of PCA Cycle 4 is comparable to that of other bahiagrass genotypes, but these data show advantages in IVDOM of Cycle 4 compared to other currently used bahiagrasses. Inferior yields with frequent harvest suggest that studies to describe the persistence of PCA Cycle 4 are needed to further assess its merit for use in production systems.
Technical Abstract: Bahiagrass (Paspalum notatum Flügge) cultivars are daylength-sensitive and have minimal cool-season production. A new genotype is less daylength sensitive and more cold tolerant, but its dry matter (DM) yield and nutritive value responses to defoliation treatments are unknown. A 3-yr field experiment studied effects of two stubble heights (4 and 8 cm) and two harvest frequencies (7 and 21 d) on diploids ‘Pensacola’, ‘Tifton 9’, and the less photoperiod-sensitive, cold-adapted (PCA) Cycle 4 bahiagrass; and the tetraploids ‘Argentine’ and Tifton 7. When harvested every 7 d, Cycle 4 had lowest total yield while Argentine had greatest yield (8.4 vs. 11.8 Mg DM ha-1). When harvested every 21 d, Cycle 4 yield was similar to the other diploids (10.6 Mg DM ha-1) and less than the tetraploids (12.6 Mg DM ha-1). Yield distribution of Cycle 4 yield was similar to other diploids and generally greater in spring but less in summer than the tetraploids. Across defoliation treatments, Cycle 4 herbage in vitro digestible organic matter (IVDOM) averaged 546 to 562 g kg-1 and was greater than all genotypes in 2006 and all but Tifton 9 in 2005. These data indicate that Cycle 4 is less productive than other bahiagrasses when harvested every 7 d during the warm season, as productive as other diploids at 21-d harvest intervals, and slightly more digestible than other currently used bahiagrasses. Inferior yields with frequent harvest suggest the persistence of PCA Cycle 4 should be studied further to assess its merit for use in production systems.