Dora Duarte de Carvalho

Avaliação de características agronômicas e morfológicas das gramíneas forrageiras Marandu, Setária e Tanzânia aos 35 dias de crescimento nas estações do ano

A field plot experiment was conducted in the Instituto de Zootecnia, Nova Odessa-SP, in a split plot design with 12 replicates, to compare, in the grasses marandu (Brachiaria brizantha Stapf. cv. Marandu), setaria (Setaria sphacelata cv. Kazungula) and tanzania (Panicum maximum cv. Tanzania-1): dry matter yield, dry matter percentage, sward height, leaf blade percentage, apical meristem height, in cuts at 35 days of growth, in the spring (21/11 to 25/12/97), summer (29/12/97 to 02/02/98), fall (13/04 to 18/05/98) and winter (28/05 to 01/07/98) seasons. The plots were the grasses and the split-plots the year seasons. Tanzania always showed high leaf blade percentage and low apical meristem height and presented the highest dry matter yield during fall season, and in the spring and winter, its dry matter yield did not differ from the other grasses, that were alike in the four seasons. The Setaria grass showed the smallest dry matter percentage in the four seasons, and the smallest leaf blade percentage, during spring and summer, which can limit its intake by the animals.

Crescimento de raízes dos capins aruana e tanzânia submetidos a duas doses de nitrogênio

ABSTRACT - The root system (pre and post grazing) characteristics of aruanagrass and tanzaniagrass under two nitrogen rates (150and 300 kg ha -1 N year) grazed by sheep in variable rotational stocking (three to seven grazing days) and variable rest period were evaluatedin this study. The treatments were assigned to a complete randomized block (two) design with two replicates (plots = grasses an d split-plots = nitrogen rates)within repeated measures. In the pre-grazing tanzaniagrass, averages within nitrogen rates and grazing p eriod showedhigher amount of dry matter of organic matter (DMOM) (1.7 mg cm -3 of soil) than aruanagrass (1.2 mg cm -3 of soil) and greater root length(119.1 cm cm -3 of soil x 68.7 cm cm -3 of soil). The 300 kg ha -1 N rate contributed to a higher root system length (107.1 cm cm -3 of soil)than the 150 kg ha -1 N rate (80.7 cm cm -3 of soil). Post-grazing root growth showed similar behavior among the variables measured andwas more evident after the second regrowth week. Considering averages within grasses, nitrogen rates and growth age, in the periodequivalent to Autumn/Winter, the DMOM growth root was of 3.9 mg 100 cm

Freqüências de corte e intensidades de desfolha em duas cultivares de alfafa (Medicago sativa, L). 1. peso, número, produção estacional e dinâmica de aparecimento das brotações basilares

The experiment was carried out at Piracicaba, SP, over one year, with two alfalfa cultivars (Crioula and CUF-101) grown in pots at open field. The weight and the basal shoot numbers were evaluated. The regrowth dynamics after the cut and seasonally of production using three cutting frequencies, 28, 35 and 42 days, and three defoliation intensities, cuts at 7 cm height with or without preservation of remaining leaf area and cut at soil level were evaluated. A completely randomized experimental design in a 3 x 3 x 2 factorial arrangement (cultivar, cut frequency and defoliation intensity), with three replications, was used. To evaluate the seasonal production, in the three alone frequency, a split plot experimental design over time was used, in which the whole plot were represented by the treatments (cultivar vs. defoliation intensity) and the split by the cuts. The 28 days cut frequency was the best for both cultivars for dry matter yield of shoots/pot, mainly in the summer time. As for shoot numbers, cut frequencies of 28 and 35 days were superior to 45 days cut frequency. Defoliation intensity of 7 cm, with preservation of the remaining leaf area, was superior to the other, as for weight and shoots numbers. The summer time showed to be favorable to production of these alfalfa cultivars. As for the appearance of regrowth shoots, more than 2/3 of shoots appeared in the two subsequent weeks after the cut, independently of cut frequency and of defoliation intensity. In tropical conditions, there is a possibility to obtain high yields with alfalfa plants since the use of about 28 days of cut intervals has to be observed. In addition, cuts closely to 7 cm from soil level are favorable, in order to explore the photosynthetic ability of the remaining leaf area and of the regrowth shoots present in the moment of cut.