Forage yield, chemical composition and morphogenesis of Megathyrsus maximus cv. Tanzânia-1 under defoliation frequencies

Abstract

The effects of defoliation frequencies (14, 21, 28, 35 and 42 days) on green dry matter (GDM) yield, chemical composition and morphogenetic and structural characteristics of Megathyrsus maximus cv. Tanzânia-1 were evaluated under natural field conditions. The increase of defoliation frequency resulted in higher GDM yields, however implied significant decreases in the levels of nitrogen, phosphorus, calcium, magnesium and potassium. The leaf appearance rate and populational tiller density are inversely proportional to defoliation, occurring the inverse for foliar senescence rate. Maximum GDM yields, number of leaves tiller-1, average leaf length, leaf expansion rate and leaf area index were obtained with defoliation frequencies of 38.5; 32.3; 40.2; 24.1 and 34.7 days, respectively. These data suggest that grass grazing at 35 to 40 days of rest period were optimal for obtain maximum yields and regrowth of rich forage.