Morphogenetic characteristics and management of Tanzania grass

Abstract

-The objective of this work was to evaluate the effect of grazing interval and period of evaluation over tissue turnover in Tanzania grass pastures (Panicum maximum cv. Tanzania) and to ascertain if herbage accumulation rate can be used as a criterion to establish a defoliation schedule for this grass in Southeast of Brazil. A randomized block design with a split-plot arrangement was used. The effect of three grazing intervals was evaluated within seven periods between October 1995 and September 1996. Responses monitored were leaf and stem elongation rates, leaf senescence rate, stem length, and tiller density. Net herbage accumulation rate was calculated using tissue turnover data. The grazing intervals for Tanzania grass should be around 38 days between October and April (spring and early autumn) and 28 days during the reproductive phase of the grass (April/May). Between May and September (late autumn and winter), grazing interval should be around 48 days. Herbage accumulation rate is not a good criterion to establish defoliation time for Tanzania grass. Studies on the effects of stem production in grazing efficiency, animal intake and forage quality are needed to improve Tanzania grass management.Index terms: leaves, elongation, senescence, grazing systems. Características morfogenéticas e manejo de capim-tanzâniaResumo -O objetivo deste trabalho foi avaliar o efeito do intervalo entre pastejos e do período de avaliação sobre algumas características morfogenéticas do capim-tanzânia (Panicum maximum cv. Tanzânia) e verificar se o manejo desse capim pode ser baseado na taxa de acúmulo de matéria seca na região Sudeste do Brasil. Foi utilizado um delineamento de blocos completos ao acaso com parcelas subdivididas no tempo. Foi avaliado o efeito de três intervalos entre pastejos e de sete períodos de avaliação entre outubro de 1995 e setembro de 1996 sobre: taxa de alongamento foliar e dos colmos, taxa de senescência foliar, altura dos colmos e densidade populacional de perfilhos. Essas informações permitiram determinar a taxa líquida de acúmulo de matéria seca. O capim-tanzânia deve ser pastejado com cerca de 38 dias no período de outubro a abril, com 28 dias na fase reprodutiva (abril/maio) e com aproximadamente 48 dias entre maio e setembro. O intervalo entre pastejos do capim-tanzânia não deve ser estabelecido apenas com base na taxa de acúmulo de matéria seca. São necessários estudos sobre as interações entre produção de hastes e eficiência de pastejo, consumo e qualidade de forragem, a fim de se determinar melhor o manejo desse capim.Termos para indexação: folha, alongamento, senescência, sistema de pastejo.

Morphogenetic traits and biomass accumulation of Brachiaria brizantha cv. Xaraés subjected to nitrogen doses

“…Many results available in the literature point a decrease in the population of tillers as pastures are kept higher (Hodgson, 1985;Sbrissia & da Silva, 2001;Sbrissia, 2004). As leaf elongation and appearance and tiller population increased, a quadratic and positive effect (P<0.0001) of N doses on leaf blade dry matter accumulation was observed, estimating a maximum value of 214.49 kg.ha -1 .day -1 of DM for a dose of 248.1 kg.ha -1 of N, which was 133% higher than the control ( Figure 5).…”

“…Parsons (1988) said the importance of controlling stalk production in the pasture, claiming that its presence could reduce the efficiency of the system in two manners: by limiting capacity of forage harvest by the animal or by reducing its nutritional value. The greatest stalk accumulation for the greatest doses of N verified is justified by the greater production of leaf blade and by the physiologic activity of the plant under non-limiting production conditions, which increase leaf tissue production flow, causing a shading of the low leaves and basal buds, stimulating stalk elongation by the plant (Sbrissia & Da Silva, 2001). By separating the effects of nitrogen fertilization during the rainy season into linear and quadratic effect (Figure 7), quadratic effect (P<0.10) of N doses was observed on stalk accumulation, with estimation of a maximum production of 84.97 kg.ha -1 .day -1 of DM for application of 326.2 kg.ha -1 of N, from which productive efficiency of 0.189 kg.ha -1 .day -1 of DM for each kg of applied N was estimated.…”

“…By separating the effects of nitrogen fertilization during the rainy season into linear and quadratic effect (Figure 7), quadratic effect (P<0.10) of N doses was observed on stalk accumulation, with estimation of a maximum production of 84.97 kg.ha -1 .day -1 of DM for application of 326.2 kg.ha -1 of N, from which productive efficiency of 0.189 kg.ha -1 .day -1 of DM for each kg of applied N was estimated. Although stalk development favors increase of DM production, it can present negative effects on use and quality of the produced forage (Santos, 2003).…”

“…Despite the morphogenetic traits being genetically determined, variables such as temperaturte, nutrient supply and humidity availability in the soil can influence them (Sbrissia & Da Silva, 2001). Morphogenetic traits can be subdivided into: leaf appearance rate; leaf elongation rate and leaf senescence rate, in addition to stalk elongation for tropical grasses (Sbrissia & Da Silva, 2001).…”

“…Morphogenetic traits can be subdivided into: leaf appearance rate; leaf elongation rate and leaf senescence rate, in addition to stalk elongation for tropical grasses (Sbrissia & Da Silva, 2001). Leaf elongation rate of the grasses is very responsive to N fertilization (Gomide et al, 2006).…”