Responses of bahiagrass to nitrogen and defoliation

Abstract

Pensacola bahiagrass (Paspalum notatum Flugge) swards pretreated with fertilizer nitrogen rates of 0 and 66-99 kg N ha1 year-1 were exposed to repeated, severe defoliation (i.e., removal of all laminae) of every day (Dl), 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 stubblestolon-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 (Dl 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.Key Words: Paspalum notatum, defoliation tolerance, tiller survival, lamina production, stubble-stolon-root system Resumen Praderas de "Bahiagrass" (Paspalum notatum Flugge) pretratatdas con dosis de fertilizacion nitrogenada de 0 y 66-99 kg N ha-1 ano-1 fueron expuestas a defoliacion severa (i.e. remocion de toda la lamina) y repetida, cada dia (D1), cada 2 dias (D2) y cada 4 dias (D4). La respuesta del zacate fue monitoreada en terminos de sobrevivencia de hijuelos, produccion de tejido laminar de la hoja y cambios en la biomasa del sistema rastrojo-estolonraiz, esto en un esfuerzo per investigar los efectos de la dosis de nitrogeno y la frecuencia de defoliacion en la tolerancia a la defoliacion, para examinar las diferencias en la habilidad para sobrevivir de los hijuelos entre generaciones de ellos y para evaluar la contribucion del sistema rastrojo-estolon-raiz a la tolerancia at a defoliacion. Al progresar los tratamientos de defoliacion hasta 12 semanas, la pradera se degrado con la disminucion de la densidad de hijuelos, la produccion de lamina y la masa de estolones y rastrojo. La tolerancia a la defoliacion en terminos de sobrevivencia de hijuelos fue influenciada solo por la frecuencia de defoliacion (D1 D2 < D4) sin un efecto significativo de la dosis de fertilizacion. No hubo diferencias en la habilidad de sobrevivencia de los hijuelos entre generaciones de hijuelos formadas antes de los tratamientos de defoliacion, sugiriendo que bajo condiciones de defoliacion severa todos los hijuelos en "Bahiagrass" fueron capaces de compartir energia y nutrientes entre los estolones co...

Deferment associated to contrasting grazing intensities affects root/shoot biomass allocation in natural grasslands

“…The main mechanism related to this adaptation and to tolerance to grazing is the capacity to store energy in reserve tissues of underground structures, a crucial feature to predominate in this environment (Strauss & Agrawal, 1999; Stowe et al, 2000). Previous work on Paspalum notatum demonstrate an increase in tillering rate, stolon length and number of primary roots in response to lower cutting heights (2 cm), in comparation to plants cut at taller heights (Hirata & Pakiding, 2003). Therefore, the great root:shoot relationship shown in our experiment for the species prevalent in the overgrazed area (prostrate and rosette growth habit) could be a strategy to “escape” from grazing and invest in underground tissues.…”

Comparisons of Turf‐Type Bahiagrass (Paspalum notatum Flügge) Lines for Root and Shoot Traits under Various Nitrogen Regimes

“…These relationships were supported by both the correlation and PCA and likely result from the plant's partitioning of energy. Because plant growth increases with increased N, the plant is likely allocating more energy from its rhizomes into shoot production, thereby reducing rhizome size (Hirata and Pakiding, 2003). The N effects in the three remaining morphological traits were not as clear.…”

Evaluation of forest grazing as a management practice to utilize and control Miscanthus sinensis in a young tree plantation in southern Kyushu, Japan

“…1984; Lemaire and Chapman 1996; Bélanger 1998). Depletion of carbohydrate is also suggested to enhance death of shoots (Hirata and Pakiding 2003). Although defoliation of M. sinensis by animals was not very intense (degree of utilization, 25–50%; Table 3), frequent removal of young leaves having high nitrogen concentrations and high photosynthetic rates is considered to be a factor contributing to low carbohydrate and nitrogen concentrations in this defoliation‐susceptible grass.…”

“…It is reported that low carbohydrate and nitrogen concentrations restrict generation and/or development of new shoots and leaves in grasses, though the response of leaf generation to nitrogen may vary with species (Vine 1983;Coughenour et al 1984;Lemaire and Chapman 1996;Bélanger 1998). Depletion of carbohydrate is also suggested to enhance death of shoots (Hirata and Pakiding 2003). Although defoliation of M. sinensis by animals was not very intense (degree of utilization, 25-50%; Table 3), frequent removal of young leaves having high nitrogen concentrations and high photosynthetic rates is considered to be a factor contributing to low carbohydrate and nitrogen concentrations in this defoliation-susceptible grass.…”