Growth Analysis of Brachiariagrasses and Tifton 85 Bermudagrass As Affected By Harvest Frequency.

Studies of growth analysis are important to understand the plant morphology and physiology to identify the determinants characteristics associated with plant productivity to optimize harvest management. The objective was to evaluate and describe the effect of harvest frequency (28 and 42 days) in two years on the growth analyses of Convert HD 364^® brachiariagrass, Marandu palisadegrass, and Tifton 85 bermudagrass in rainfed conditions. The experiment was carried out in Piracicaba, Brazil. Data were collected during 2 years (from September 2011 to March 2012 and September 2012 to March 2013). The experimental design was a randomized complete block in a factorial arrangement (3 x 2) with four replications. The response variables were: leaf area index (LAI), crop growth rate (CGR), relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR) and leaf weight ratio (LWR). Despite the Tifton 85 present lower LAI (2.22) than the Convert (4.84) and Marandu palisadegrass (3.85), for CGR Tifton 85 was similar (5.27 g m^-2 d^-1) to Convert (5.13 g m^-2 d^-1), and Marandu palisadegrass has lowest CGR (4.44 g m^-2 d^-1). Tifton 85 also had higher NAR (7.43 g m^-2 d^-1) than Convert (2.76 g m^-2 d^-1) and Marandu palisadegrass (2.70 g m^-2 d^-1) in two years. Convert had higher LWR (0.51 g g^-1) than Marandu palisadegrass (0.45 g g^-1) and this than Tifton 85 (0.40 g g^-1). This results suggest that despite the Tifton 85 had highest photosynthetic efficiency, Convert HD 364 has a greater leaves mass. The lowest LAR in Tifton 85 can evince the need for less leaf area to produce the same amount of dry matter that Convert HD 364 and Marandu palisadegrass. The highest RGR in 28 days of regrowth and the first year is due the highest LAR, thus RGR was more influenced by LAR than NAR.