Francisco Humberto Dübbern de Souza

Avaliação agronômica de linhagens selecionadas de guandu (Cajanus cajan (L.) Millsp)

With the purpose of re-evaluating seventeen pigeon-pea lines originated from accessions previously selected for favorable agronomic characteristics, experiments were installed in five locations of the State of Sao Paulo. The confirmation of those characteristics was necessary because the original accessions presented various degrees of mechanical mixtures and segregation and were submitted to purification process in pollination controlled conditions. In those trials, the lines were cut in several occasions to evaluate forage yield. Each time, it was determined the number of plants in each parcel and its average height. Also it was determined their crude protein and tannins contents. Among the tested lines, g58-95 e g127-97 confirmed to have low plants, g94, g167-97 and g29b-94, confirmed to offer good forage yields, while line g146-97 presented good initial forage yields.

Frequências de cortes em nove leguminosas forrageiras tropicais herbáceas cultivadas ao sol e sob plantação florestal

O objetivo deste trabalho foi estudar a producao e o valor nutritivo de nove especies de leguminosas forrageiras herbaceas tropicais, cultivadas sob dois niveis de irradiacao luminosa e seis frequencias de corte na estacao chuvosa, em Anhembi (SP), Brasil. Parcelas puras foram estabelecidas ao sol e sob plantacao de Eucalyptus grandis, com 8 anos de idade, com 1.000 arvores/ha, que interceptou mais de 80% da radiacao luminosa incidente. Avaliou-se a taxa de acumulo de materia seca, a proteina bruta e a digestibilidade in vitro da materia seca em amostras de plantas colhidas em intervalos de 30, 60, 90 e 180 dias, com cortes adicionais aos 120 e 150 dias. Sob pleno sol, as leguminosas testadas toleraram cortes mais frequentes (intervalos de 30 - 90 dias), exceto o Lablab. Na sombra, o grau de tolerância variou conforme a especie; em termos de producao de MS e de persistencia, a Centrosema e a Pueraria se destacaram dentre as demais leguminosas comparadas, quando os cortes foram realizados em intervalos de 60 dias, enquanto o Arachis e o Estilosantes foram os mais produtivos quando os cortes ocorreram em intervalos de 120 dias, mantendo o valor nutricional. O Alysicarpus e a Aeschynomene nao persistiram sob o nivel de sombreamento que prevaleceu nesse experimento.

Estudo comparativo de métodos para a avaliação do vigor de sementes de sorgo (Sorghum vulgare Pers.)

Six methods were tested comparatively for the evaluation of sorghum seed quality in an attempt to determine the efficiency of the different methods. The following methods were tested: standard germination, first count, speed of germination, ammonium chloride test, accelerated aging and seedling emergence. Results showed that among the tests performed, standard germination and first count were the least sensitive in the evaluation of the physiological condition of seeds. The ammonium chloride and speed of germination tests diferenciated more accurately the degree of deterioration of seeds.