RESUMO - Productivity and Chemical Composition of Tropical Grasses in the Forest Zone of PernambucoABSTRACT -This work was carried out to evaluate the productive potencial and chemical composition of five grasses (Pennisetum purpureum Schum. cv. Pioneiro, P. purpureum Schum cv. Mott; Panicum maximum Jacq. cv. Mombaça, P. maximum Jacq cv. Tanzânia, e Brachiaria brizantha (Hochst) Stapf. cv. Marandu). The cuts were performed at 35 days of intervals and 40 cm above ground. Pioneiro showed higher DM yield (7.35 t DM/ha/35 days) when compared to the Dwarf Elephantgrass (5.28 t DM/ha/35 days) and Tanzânia grass (5.23 t DM/ha/35 days), being similar to the others. Brachiaria brizantha presented the highest total tillering (538.72/m 2 ) however the aerial tiller weight was the lowest for this species. The cultivars of P. purpureum showed higher aerial tillering and lower basal tillering, when compared to the cultivars of P. maximum. The CP concentration ranged from 6.96 to 10.20% and the cultivar Pioneiro presented the highest value. No difference was found among the forages for NDF and ADF, and the mean values were 73.83 and 39.20%, respectively. At the evaluated cut interval, the forages presented a high proportion of leaves (> 80%), showing potential to be used on livestock pasturebased operations in the Forest Zone of Pernambuco.

Use of morphologic descriptors and trait heritability in dwarf elephant grass clonesABSTRACT -The experiment was carried out with the objectives to evaluate the use of morphologic descriptor in the characterization and selection of dwarf elephant grass genotypes, and to evaluate the heritability of the evaluated traits. Nine dwarf elephant grass clones were used (Taiwan A.146 -2.14, Taiwan A.146 -2.27, Taiwan A.146 -2.37, Taiwan A.146 -2.114, Merker México -6.2, Merker México -6.5, Merker México -6.31, cv. Mott, and CNPGL92F198.7) was allotted to a randomized complete block design was used with three replications. The morphologic descriptors were applied every 60 days after the staging cut. A total of five cuts were performed at 60-day intervals using a height of 10 cm from ground level. Among the evaluated dwarf elephant grass clones the tallest ones were more desirable, and this trait should be considered at the moment of selection. Heritability estimate was high for all evaluated traits of dwarf elephant grass, varying from 66% for sheath wax to 100% for mid-rib color. The Taiwan A.146 -2.37 clone was similar to the Mott cultivar. Heritability values showed genetic variability among clones, detected at 60 days regrowth. Some of the used morphologic descriptors allowed characterization of the evaluated genotypes. The clones Taiwan A. 146-2.27, Taiwan A. 146-2.37, Taiwan A. 146-2.114, and Merker México 6.31were the tallest and showed greater total tillering intensity, and were more desirable, presenting greater potential for use under cutting.Key Words: desirability, dwarf elephant grass, forage breeding IntroduçãoO capim-elefante (Pennisetum purpureum Schum) tem sido bastante estudado em programas de melhoramento genético em todo o Brasil visando à seleção de materiais superiores e adaptados a cada realidade ambiental do País (Freitas et al., 2004). A aplicação dos descritores morfológicos de capim-elefante visa, geralmente, caracterizar novos R. Bras.

O estudo visou caracterizar uma coleção de 71 clones de capim-elefante e selecionar os mais promissores para serem testados sob pastejo. A caracterização foi realizada na Estação Experimental do Cedro/IPA, no município de Vitória de Sto. Antão/PE, nas estações chuvosa e seca. Cada clone foi representado por parcelas não repetidas de 10 m². Segundo análise de correlação linear, os clones mais produtivos em relação à MS, também apresentaram maiores alturas de planta e de meristemas apicais, diâmetros de colmo, relações colmo/folha (C/F), números de perfilhos basais e total e comprimentos de folha. Excetuando-se a relação C/F, as mesmas características também correlacionaram-se positivamente com a produção de lâmina foliar (LF). Foi observada uma correlação linear positiva e altamente significativa (r = 0,9517) entre as produções de MS e de LF. Baseando-se nos materiais que apresentaram as maiores produções de LF/área, foram selecionados 10 clones: Mineirão/IPEACO, Hexaplóide, Mole de Volta Grande, King Grass, 591-76 ou Cameroon, CE 5 A.D., Gigante de Pinda, CE 4 A.D., Elefante da Colômbia e Vrukwona

Roots are an important component controlling grassland sustainability. Th ey can act as a C sink of atmospheric CO 2 and supply essential nutrients for plant growth. Pasture management strategies intended to increase forage and animal production can also aff ect root biomass, root composition, and root decomposition. Th is 2-yr study evaluated the eff ects of N fertilization and stocking rate (SR) on root decomposition and root chemical composition of grazed elephantgrass (Pennisetum purpureum Schum. '381') pastures. Treatments consisted of a factorial combination of three SR (2.0, 3.9, and 5.8 animal unit [AU] ha -1 , 1 AU = 450 kg body weight) and three N levels (0, 150, and 300 kg N ha -1 yr -1 ). Greater turnover rates were observed in Year 2 (k = 0.00215 g g -1 d -1 ) than Year 1 (k = 0.00178 g g -1 d -1 ). Increasing SR increased root decomposition linearly (P = 0.05) at 0 kg N ha -1 ; nevertheless, when N was applied at 300 kg N ha -1 , root decomposition decreased (P = 0.003). Nitrogen fertilization reduced root C to N ratio and increased root N and root acid detergent insoluble nitrogen (ADIN) concentrations in Year 1, but no eff ects were observed in Year 2. Root N disappearance followed a negative single exponential model and increased with increasing levels of N fertilization. Pasture management practices such as fertilization and grazing management can alter the root quality and turnover; thus, development of strategies to manage belowground decomposition is a key to long-term grassland sustainability.