Influência do porte da planta e do sistema de cultivo sobre o crescimento de capim-elefante (Cenchrus purpureus (Schumach.) Morrone)

Abstract

Studying the growth of elephant grass [Cenchrus purpureus (Schumach.) Morrone] can help to understand the productive and qualitative differences between plant size and cropping systems. In this context, the present study aimed to evaluate structural attributes and growth indices of elephant grass genotypes of different sizes (high size: IRI-381 and Elephant B; low size: Mott and Taiwan A-146 2.37) in monoculture and intercropped with butterfly pea (Clitoria ternatea L.) throughout the regrowth period at different season of the year (wet and dry season). The experimental treatments were randomized in complete blocks, in a factorial arrangement (2 × 2), with two sizes (short and tall genotypes) and two cropping systems (monoculture and intercropping). Plant and stem height, leaf area index, light interception, absolute growth, relative growth and net assimilation rates, specific leaf area, leaf area ratio and light extinction coefficient were studied every 15 days. The intercropping with butterfly pea and the size of the plant promotes lower growth of elephant grass, in isolation, regardless of the season of the year. The growth indices showed a specific response for each season of the year, according to the regrowth age, cropping system and plant size. In the wet season, the absolute growth rate was higher in genotypes under monoculture only at 60 days (135.94 g.m-2.day-1 in monoculture vs. 50.51 g.m-2.day-1, under intercropping), while the relative growth rate was higher in tall genotypes, regardless of regrowth age, with averages of 0.14 g.g-1.day-1 for tall genotypes and 0.13 g.g-1.day-1 for short genotypes. In the dry season, the growth of the genotypes under monoculture and with tall size did not show growth indices different from those intercropped with butterfly pea and with short size. These results can help to define different cutting management strategies for elephant grass intercropped with butterfly pea, as well as according to the size of the grass plant, at different season of the year.