Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/1999
Publication Date: N/A
Interpretive Summary: Research to improve the yield of Pensacola bahiagrass led to the development and release of the cultivar Tifton 9 and continued to generate further advanced selection cycles. Previous research has documented the morphological changes that have accompanied selection for increased yield. Plants of selected populations are progressively more erect, taller, longer-leafed, but with decreased individual plant diameter. Our search was conducted to find out how these changes in plant structure influenced production and persistence under mechanical harvest or grazing. Selected populations (Tifton 9, RRPS cycle 14) were generally higher yielding than Pensacola as expected, but responded to mechanical harvest similarly: highest yield generally resulted from lowest cutting height and longer regrowth interval. The most advanced germplasm evaluated, RRPS cycle 14, was less persistent than Tifton 9 or Pensacola when stocked continuously at high grazing pressure. The potential for greater productivity of Tifton 9 compared to Pensacola was reflected by similar animal growth, but higher carrying capacity and comparable stand persistence. Continuous stocking at high grazing pressure cannot be recommended for RRPS cycle 14 or other, more advanced bahiagrass populations.
Technical Abstract: Recurrent restricted phenotypic selection has increased spaced-plant yield of Pensacola bahiagrass (Paspalum notatum Fluegge var. saurae Parodi). Base population plants are prostrate; high-yielding genotypes are upright. Response to defoliation of 3 populations Pensacola (P), Tifton 9 (T9) and RRPS cycle 14 (C14) was examined. Cutting height (15 or 100 mm) and regrowth interval (2-, 4- or 8-wk) were varied. A split-split plot arrangement of regrowth interval, cutting height and selection cycle was used for 3 yr. Yield (7030 kg ha-1) was maximized by low cutting height and 8-wk regrowth interval during the first year. In yr 2, a 4-wk regrowth interval and low cutting height produced the highest (P<0.05) yields (11220 kg ha-1). Mean yields of cycle 9 (7650 kg ha-1) and 14 (7320 kg ha-1) were greater (P<0.05) than cycle 0 (6500 kg ha-1), but response of selection cycles to cutting height and regrowth interval varied and was not consistent among years. Response of P, T9 and C14 bahiagrass to defoliatio from continuous stocking was evaluated for 2 yr. Herbage mass was greater (P<0.05) for T9 (1670 kg ha-1) and C14 (2000 kg ha-1) than for P(1420 kg ha-1). Carrying capacity of T9 (935 d ha-1) was greater (P<0.14) than P (855 d ha-1) but similar ( P>0.05) to C14 (896). Bahiagrass declined in all pastures, but rate of decline was similar for P and T9. Lower (P<0.05) bahiagrass stands of C14 were evident as early as the end of the first grazing season. Potential for greater productivity of T9 compared to P was reflected by similar animal growth at higher carrying capacity and comparable stand persistence. Continuous stocking at high grazing pressure cannot be recommended for C14 or other, more advanced, populations.