Responses of bahiagrass to nitrogen and defoliation

Pensacola bahiagrass (Paspalum notatum Flugge) swards pretreated with fertilizer nitrogen rates of 0 and 66-99 kg N ha(-1) year(-1) were exposed to repeated, severe defoliation (i.e., removal of all laminae) of every day (D1), every 2 days (D2), and every 4 days (D4). Responses of the grass were monitored in terms of tiller survival, lamina production and changes in the mass of the stubble-stolon-root system, in an effort to investigate the effects of nitrogen rate and defoliation frequency on defoliation tolerance, to examine differences in survival ability of tillers among tiller age cohorts, and to evaluate contribution of the stubble-stolon-root system to defoliation tolerance. With the progress of defoliation treatments over 12 weeks, the swards degraded with decreasing tiller density, lamina production, and mass of stubble and stolons. Defoliation tolerance in terms of tiller survival was influenced only by defoliation frequency (D1 approximate to D2 < D4), with no significant effect of nitrogen fertilizer rate. There were no differences in survival ability of tillers among age cohorts formed before the defoliation treatments, suggesting that all tillers in bahiagrass were able to share energy and nutrients in connecting stolons under severe defoliation. It was confirmed that stolons play a key role in defoliation tolerance in bahiagrass as the main storage organ supporting aboveground parts, whereas the contribution of roots seems nil.