Características produtivas de clones de Pennisetum sp. sob lotação intermitente, na Zona da Mata Seca de Pernambuco

Abstract

The experiment was carried out at the Estação Experimental do Instituto Agronômico de Pernambuco (IPA), in the municipality of Itambé-PE, from March 2008 to March 2009, to evaluate the productive traits of intermittently grazed Pennisetum sp. clones. Three elephant grass clones (IRI-381, Venezuela A. D. and Elefante B.) and one millet hybrid (Pennisetum glaucum) with elephant grass (Pennisetum purpureum Schum.) (Hexaploide), under grazing, were evaluated. A randomized block design with nine replicates was used. The grazing cycles in the rainy season were of 35 days, with 32 days of rest and 3 days of grazing and in the dry season, of 70 days, with 67 days of rest and 3 days of grazing. Plant height (cm) in the pre- and post-grazing, forage accumulation rate (kg DM/ha/day), forage total accumulation (kg DM/ha/yr), leaf density (kg DM leaf/ha/cm) in the pre and post-grazing, botanical composition in the pre-grazing and discovered soil (%) in the pre- and post-grazing, during nine cycles of grazing, were the traits evaluated. Cycle and clone significant interaction on the plant height in the pre-grazing was observed, and Venezuela clone showed the highest value, on April, August, September and October 2008 and differed from the other clones. Plant height in the post-grazing showed significant difference only for cycle, with greater values on August (105.5 cm), September (103.2) and October (101.8 cm). Clone effect on forage accumulation rate was observed only in the dry season, when IRI 381 clone showed the highest value (86.6 kg DM/ha/day) and Venezuela, the smallest one (31.9 kg DM/ha/day); the same behavior was observed for total accumulation. Leaf density in the pre- and postgrazing was significantly different for both cycle and clone. March 2008 was the highest leaf density cycle in the pre-grazig for both clones and showed the greatest value for IRI 381 with 36.6 kg DM leaf/ha/cm. Neither cycles nor clones affected the botanical composition, where the elephant grass stood out, although 36 different species were found in the area. Venezuela was the clone that promoted the greater discovered soil in the pregrazing, with 25.4% on March 2008, however, only cycle effect on discovered soil was detected. IRI-381 clone showed the greatest potential for grazing. No grazing effect on soil predominance and covering of elephant grass pasture is observed.