Germination potential of cuttings and evaluation of morphoagronomic characteristics of six cultivars of elephant grass (Pennisetum purpureum Schum.) for energy purposes in Campos dos Goytacazes, RJ

Abstract

The elephant grass (Pennisetum purpureum Schum.) is a tropical forage with great efficiency in light utilization and high biomass production, which in addition to the traditional use in animal feed, it has also has been appointed to direct combustion and to obtain charcoal. Currently, energy demand has become a worldwide problem and the search for alternative energy sources is increasing. Thus, the search for biomass varieties adapted to the different ecosystems of the State of Rio de Janeiro becomes more intense. The objective of this study was to characterize the potential for germination of six genotypes of elephant grass through germinative propagation and to evaluate their morphological characteristics at the time of the cut, relating them mainly with the dry matter production aiming for energy demand. The experiment was conducted in randomized block design with three replications, installed in the area of agreement of the Pesquisa Agropecuária do Estado do Rio de Janeiro company (PESAGRO - RIO) at the Universidade Estadual do Norte Fluminense Darcy Ribeiro (UENF) in Campos dos Goytacazes, RJ. It was characterized the germination of six genotypes of elephant grass (1-Cubano Pinda, 2-Mercker Pinda México, 3-Mercker 86/México, 4-Cameroon/Piracicaba, 5-Guaçú/ IZ.2, 6-Roxo Botucatu) during five weeks. Their morphological characteristics were evaluated at six months old, and estimated the percentage of dry matter (% MS) and dry matter yield in t ha-1 (PMS). Regarding the counts on the number of tillers sprouted per linear meter, there was significant difference (P<0.01) for readings taken at 30 and 37 days after planting, with averages of 8.08 and 8.29 tillers per linear meter , respectively. The coefficients of variation were between 20 and 32%. With the Scott and Knott cluster test, at 5% probability, the group with the highest number of tillers was formed by genotypes Cubano Pinda, Mercker 86 - México, Guaçú/ IZ.2 and Roxo Botucatu. There was no significance (P> 0.05) for interaction between genotype and weeks and for significant effect (P <0.01) for genotype in the readings of germinated tiller number per linear meter. By linear regression analysis there was significance for all genotypes to linear first degree effect (P <0.05). For the morphological characteristics, the variables number of tillers (NP), green matter production (PMV), percentage of dry matter (% MS) and dry matter production (PMS) there was significant difference (P <0.05), and average values of 28.60 tillers, 36.11 t.ha-1, 27.79% and 9.95 t.ha-1, respectively. The coefficients of variation were considered medium, being the lowest one 8.19% for MS and the greater one, 28.65%, found in PMS. In general, the genotypes that performed better in terms of both number of tillers germinated per linear meter and in the morphological characteristics studied were Cubano Pinda and Roxo Botucatu, standing out as promising genotypes for biomass production for energy purposes at weather and soil conditions of Campos dos Goytacazes.