Fluxo de biomassa em capim-tanzânia pastejado por ovinos sob três períodos de descanso

Abstract

RESUMO -Avaliou-se o fluxo de biomassa em Panicum maximum cv. Tanzânia pastejado por ovinos com três períodos de descanso (PD), definidos pela expansão de 1,5; 2,5 e 3,5 novas folhas por perfilho, em um delineamento inteiramente casualizado, com duas repetições (piquetes). Estimaram-se as taxas de alongamento de lâmina foliar total (TAlF), de senescência de lâminas foliares remanescentes do pastejo anterior (TSFA), de senescência das novas folhas formadas no PD (TSFP) e de senescência total (TSFT=TSFA+TSFP), a taxa de alongamento das hastes (TAlH), a razão entre as TAlF das folhas 1 e 2 (razão TAlF1/TAlF2), a densidade populacional de perfilhos (DPP), o filocrono e as taxas de crescimento (TCC) e de acúmulo (TAC) da cultura. A razão TAlF1/2 não foi afetada pelos PD, mas reduziu ao longo dos ciclos na pastagem sob PD 3,5. A TAlF não foi afetada pelos PD. A TAlH, a TSFA e a TSFT na pastagem sob PD 1,5 foram menores que nas demais. Houve TSFP somente na pastagem sob PD 3,5. O filocrono da pastagem sob PD 1,5 foi superior ao observado nas demais. A densidade populacional de perfilhos (DPP) da pastagem sob o PD 2,5 foi similar à verificada na pastagem sob PD 1,5 e superior à verificada sob PD 3,5. Houve redução na DPP ao longo dos ciclos na pastagem sob PD 3,5. As taxas de crescimento (TCC) e de acúmulo (TAC) foram superiores na pastagem sob PD 2,5. O prolongamento do PD elevou as TAlH e TSFT e reduziu a DPP e a TAC. Portanto, o PD do capim-tanzânia pastejado por ovinos não deve exceder o tempo necessário à expansão de 2,5 novas folhas por perfilho.Palavras-chave: lotação rotativa, Panicum maximum, taxa de acúmulo de forragem, taxa de alongamento das hastes, taxa de alongamento foliar, taxa de senescência foliar Biomass flow in tanzaniagrass pasture under three resting periods grazed by sheepABSTRACT -The biomass flow in Panicum maximum cv. Tanzânia pasture grazed by sheep under three resting periods (PD), defined by the expansion of 1.5; 2.5 and 3.5 new leaves per tiller (1.5F; 2.5F and 3.5F, respectively) was evaluated in a randomized completely design with two replicates (paddocks). It was determined the leaf elongation rate (TAlF), the residual leaf senescence rate (TSFA), the post-grazing leaf senescence rate (TSFP) and the total leaf senescence rate (TSFT), the stem elongation rate (TAlH), the TAlF of leaves 1 and 2 ratio (TALF1/2), the tiller population density (DPP), the phylochron and the crop growth (TCC) and accumulation (TAC) rates. The TAlF1/2 ratio was not affected by the PD, however, it decreased over the cycles at the 3.5F PD pasture. The TAlF was not affected by the PD. The TAlH was inferior at the 1.5F PD pasture, as well as the TSFA and the TSFT. There was TSFP only at the 3.5F PD pasture. The phylochron of the 1.5F PD pasture was superior to the others. The DPP of the 2.5F PD pasture was similar to that of the 1.5F PD pasture, and it was superior to the 3.5F PD pasture. There was reduction of the DPP following the cycles at the 3.5F PD pasture. The TCC and the TAC of the 2.5F PD pasture were super...

Biomass flow in massai grass fertilized with nitrogen under intermittent stocking grazing with sheep

“…On the other hand, it is worth highlighting the negative effects caused by increased proportion of stem in total biomass, with direct reflection on the forage quality (reducing the forage quality) by decreasing the leaf/stem ratio, thus reducing the nutritional value of the biomass produced (Cândido et al, 2006;Silva et al, 2007a) and its use by grazing animals (Silva et al, 2007b). Moreover, the intense elongation of stems negatively influences the feeding behavior of grazing animals (Chacon & Stobbs, 1976) and the forage intake (Silva et al, 1994b), due to the physical limitation imposed by increased stem participation and also due to the selectivity of animals for leaf blades (Benvenutti et al, 2006).…”

“…The senescence rate of leaves remaining after grazing is an indicative of the adjustment of defoliation frequency to the canopy physiology, once a pasture managed for a high efficiency of use of the produced forage should prevent the senescence of leaves formed in the regrowth, i.e., should present a SRLAG equal or close to zero (Cândido et al, 2006).…”

Relationship between the morphogenesis of Italian ryegrass cv. 'BRS Ponteio' with forage and seed production

“…The stem expansion rate (SER) was negligible for the cultivar under research up to the first cut, as a result, the forage harvesting was composed only by leaves (Table 1). CANDIDO et al (2006) say that a closed canopy, changes the quantity and quality of light, modifying the brightness detected by the phytochrome. Thus, for improving the luminous environment, the internodes lengthen, thereby inhibiting tillering.…”

“…Therefore, the reduction of the tillering (sloping high coefficient) at insignificant levels (Figure 3c). At this time, the partition of the assimilated is treated as a priority to the lengthening over the emergence of new tillers (CANDIDO et al, 2006) and the expansion and leaf appearance (with a sloping high coefficient - Figure 2c and 3c, respectively). The sensitivity to the photoperiod and the appearance of the last leaves of the tillers can also explain the sloping of appearance rates and leaf expansion.…”

Características estruturais de milheto sob pastejo rotativo com diferentes períodos de descanso

“…Segundo Gomide & Gomide (2000), nesse nível de inserção, as folhas têm maior trajeto a percorrer dentro do pseudocolmo, resultando em maior tamanho de folhas ao longo do ciclo de crescimento. Posteriormente, com o progressivo alongamento dos entrenós e a elevação do meristema apical, a distância percorrida pela folha emergente Dias após a semeadura LV 1,5 a 2 F 2,5 a 3 F 3,5 a 4 F perfilhamento (Candido et al, 2006). Essas observações poderiam explicar a maior altura e a menor densidade de perfilhos basilares com o aumento do período de descanso (alturas da pastagem no momento pré-pastejo -PD 1,5 a 2 folhas = 55 cm; PD 2,5 a 3 folhas = 82 cm e PD 3,5 a 4 folhas = 106 cm).…”