Brachiaria and Cynodon are important pasture grasses in Brazil. Convert HD 364 (Dow AgroSciences, São Paulo, Brazil) brachiariagrass (Brachiaria hybrid CIAT 36087; also known as Mulato II) is a new hybrid released for use in a broad range of environments. It has high nutritive value and yield, but there are no year‐round comparisons, including the dry season, with other pasture grasses. Forage accumulation and crude protein (CP), neutral detergent fiber (NDF), and in vitro digestible organic matter (IVDOM) concentrations were evaluated for Convert HD 364, Marandu palisadegrass {B. brizantha (Hochst. ex A. Rich.) R. D. Webster [syn. Urochloa brizantha (A. Rich.) Stapf]; CIAT 6297}, and Tifton 85 bermudagrass (Cynodon spp.) during dry and rainy seasons from 2011 to 2013. Irrigated and rainfed plots were harvested every 28 and 42 d. Convert HD 364 had similar or greater forage accumulation (17.9–22.8 Mg DM ha−1) than Marandu and Tifton 85 (15% greater than Marandu and 12% greater than Tifton 85 when irrigated and harvested every 28 d). Tifton 85 CP concentration was 140 g kg−1, greater than that of the other grasses when harvested every 28 d and irrigated. Convert HD 364 (537 g kg−1) NDF concentration was least, regardless of irrigation, harvest frequency, or season. This was associated with IVDOM concentration greater than 650 g kg−1, similar to that of Marandu. Convert HD 364 is a viable option for diversification of pasture‐based animal production systems in tropical areas due to high forage accumulation and nutritive value when fertilized and well managed.

No abstract

Brachiaria and Cynodon are two of the most important pasture grasses worldwide. Computer model simulations can be used to study pasture species growth and physiological aspects to identify gaps of knowledge for genetic improvement and management strategies. The objective of this research was to compare the performance relative to calibrated parameters of the CROPGRO‐Perennial Forage Model (CROPGRO‐PFM) for simulating three different species (“Marandu” palisadegrass, “Convert HD 364®” brachiariagrass and “Tifton 85” bermudagrass) grown under similar management. The field experiment consisted of two harvest frequencies, 28 and 42 days, under irrigated and rainfed conditions. Data used to calibrate the model included regular forage harvests, plant‐part composition, leaf photosynthesis, leaf area index, light interception and plant nitrogen concentration. The simulation of biomass production of the three grasses presented d‐statistic values higher than 0.80, RMSE ranging from 313 to 619 kg/ha and ratio observed/simulated ranging 0.968 to 1.027. Harvest frequency treatments of 28 and 42 days were well simulated by the model. A sensitivity analysis was conducted to evaluate the most influential parameters needed for model calibration and to contrast the grasses, showing that the differences among the three grasses are mostly driven by plant‐part composition and assimilate partitioning among plant organs.

(1) Recebido para publicação em março de 2008 e aprovado em fevereiro de 2010.