Gas exchanges, chemical composition and productive characteristics of tropical grasses deferred I: cultivars BRS Massai and BRS Tamani

ABSTRACT This study aimed to evaluate the physiological parameters, the productive characteristics, structural and chemical composition of Megathyrsus maximus (syn. Panicum maximum) cultivars BRS Massai and BRS Tamani submitted to different periods of deferment and moments of use. The experimental design was randomized complete block design in a factorial scheme 2 x 2 x 3, being two grass cultivars (Massai grass and Tamani grass), two deferment periods (rainy season and dry-rainy transition) and three sealing times (40, 80 and 120 days). Both cultivars had higher leaf transpiration rate when used for 40 days of deferment (0.63 μmol/m2/s). It was observed that the cultivar BRS Massai presented higher photosynthetic rate (P<0.05) to 40 days of deferment (1.10 μmol/m2/s), higher rate of production and forage accumulation when used for 40 days. On another side, there was a greater efficiency in the use of water during the period of transition in the pastures sealed for 80 and 120 days (64.60 and 62.30 kg DM/ha/mm, respectively). A reduction (P<0.05) of total digestible nutrients (TDN) and crude protein (CP) was observed with the increase in pasture sealing time. In general, the deferment in the transition period allows the use of forage without greater productive and nutrient losses up to 80 days of sealing for the cultivar BRS Tamani and up to 40 days for BRS Massai.