Características morfogênicas e estruturais de capim-mombaça em três densidades de cultivo adubado com nitrogênio

Abstract

RESUMO -Objetivou-se com este trabalho avaliar o efeito da adubação nitrogenada e da densidade de plantas nas características morfogênicas e estruturais do capim-mombaça (Panicum maximum Jacq. cv mombaça). O experimento foi realizado em delineamento de blocos casualizados, com 12 tratamentos e três repetições, com quatro doses de nitrogênio (0, 80, 160 e 320 kg/ha.ano) e em três densidades (9, 25 e 49 plantas/m 2 ) nas quatro estações do ano. O corte foi realizado a 30 cm do nível do solo, quando o dossel atingia 95% de interceptação luminosa. Foram mensuradas as taxas de aparecimento foliar, senescência e alongamento foliar, filocrono, taxa de alongamento de pseudocolmo, número de folhas vivas, duração de vida das folhas, número de perfilhos totais por touceira e taxas de aparecimento e mortalidade dos perfilhos totais. A adubação nitrogenada influenciou positivamente as taxas de aparecimento foliar e de perfilhos totais (outono e inverno), as taxas de alongamento foliar (primavera e verão) e de pseudocolmos (verão), a taxa de senescência foliar (outono, inverno, primavera e verão) e o número de folhas vivas e de perfilhos totais (primavera e verão). A adubação também influenciou positivamente o perfilhamento do capim-mombaça. As densidades mais elevadas aumentaram as taxas de alongamento e senscência foliar e diminuíram o número de perfilhos. A adubação nitrogenada reduz o filocrono e a duração de vida das folhas (primavera e verão), mas não influencia a taxa de mortalidade de perfilhos. Palavras-chave: adubação nitrogenada, interceptação luminosa, perfilhoMorphogenic and structural characteristics of Panicum maximum Jacq. cv. Mombaça under three densities of fertilization with nitrogenABSTRACT -The objective of this experiment was to evaluate the effect of the nitrogen fertilization and density of plants in the morphogenic and structural characteristics of mombaça grass (Panicum maximum Jacq.). The experiment was set up as a completely randomized block design with 12 treatments and three repetitions, with four applications of nitrogen (0, 80, 160 and 320 kg/ha.year) and three densities (9, 25 and 49 plants/m 2 ) in the four seasons of the year. The plot was cut at 30 cm from the ground, when the light interception reached 95%. The following measures were done: leaf appearance and elongation rate, Phyllochron, leaf senescence rate, number of live leaves, leaf lifetime, stem elongation rate and rates of appearance and mortality of the total tiller. Nitrogen fertilization positively influenced the leaf and tiller appearance (fall and winter) rates, leaf elongation (spring and summer), and stem elongation (summer) rates, leaf senescence (all the stations) rate and number of live leaves and tillers (spring and summer). The fertilization also influenced positively the tillering of mombaça grass. Higher densities of plants increased the elongation and leaf senescence rates and decreased the number of tillers. Nitrogen fertilization reduces the phyllocron and life lenght of leaves (spring and summer), but does not...

<b>Morphogenesis in pastures with Tanzania grass fertilized with nitrogen doses under a grazing system

“…This fact was probably due to the parceling of N application which was insufficient to increase LER and LLR, whereas the variations between the seasons were due to abiotic factors (Pereira et al, 2011). In current experiment, data were lower than those by Martuscello et al (2005) who reported an increase of the variable in Tanzania and Xaraés grass in hothouses when compared to rates in N-less applications.…”

“…Higher SLR rates were registered during the summer (0.33 cm shoot ). The above indicates that fertilization with N enhanced the lengthening of the stem (Pereira et al, 2011). Data show a trend that N fertilization (doses 300 and 450 kg ha -1 ) at shorter grazing periods is an important tool in the control and development of stems and consequently of the forage canopy structure (Figure 3).…”

“…According to Martuscello et al (2006), higher DLL rates and lower NLL rates in pastures without fertilization was probably due to N effect which anticipated the senescence process in plants through the translocation of nutrients for the expansion of new leaves. In their research on Mombaça grass, Pereira et al (2011) reported an influence (p > 0.10) on DLL in the autumn and winter. However, N fertilization affected linearly and negatively the variable during spring and summer.…”

“…Animal Sciences Maringá, v. 37, n. 3, p. 235-241, July-Sept., 2015 development of pastures. It provides the plant with a faster growth, increase in number, weight and size of shoots and foliar area index (Pereira et al, 2011). According to Fagundes et al (2006) growth and endurance of grass are often limited by the soil's N deficiency since the nutrient accelerates the initiation and expansion rate of new leaves and increases the shoot's strength.…”

Momento de aplicação do nitrogênio e algumas variáveis estruturais e bromatológicas do capim-massai

“…A TApP com ausência de aplicação de nitrogênio foi de 30,94%, e com 120mg/dm³ de N de 53,2%, aumento de 42%, percentuais próximos aos encontrados por Pereira et al (2011), que, quando trabalharam com capim-mombaça em três densidades de cultivo e adubado com nitrogênio, obtiveram 34,9 e 46,0% de TApP na ausência e na presença de N (320kg/ha), respectivamente. É fácil observar que o capimmassai tem como característica marcante o perfilhamento intenso.…”