Israel Alexandre Pereira Filho

Atividade alelopática da leucena sobre espécies de plantas daninhas

Allelopathy is the direct or indirect effect of one plant on another through substances liberated into the environment, and occurs widely in natural plant communities. The secondary metabolites or natural products involved in allelopathy are called allelochemicals and can be produced in different parts of the plants. The purpose of this study was to determine the allelopathic potential of the aerial part of Leucaena leucocephala on the weeds Desmodium purpureum, Bidens pilosa and Amaranthus hybridus. Bioassays were carried out in laboratory and in greenhouse with aqueous extracts of the aerial part of leucaena in concentrations of 100, 50, 25, 12.5 % (v v-1). The aqueous extract showed major effect over the weeds when applied to filter paper. The allelopathic potential of leucaena varied with weed species, but B. pilosa and A. hybridus were the most sensible species to the extract in both bioassays. Mimosine was quantified by HPLC in concentrations directly correlated to extract concentrations, indicating this allelochemical as the possible substance involved in effects on weed germination and development.

Efeito do extrato aquoso de leucena na germinação e no desenvolvimento do milho

Foram desenvolvidos bioensaios, na Embrapa-Centro Nacional de Pesquisa de Milho e Sorgo (CNPMS), para avaliar o efeito de extratos aquosos, a frio e a quente, da parte aerea de leucena (Leucaena leucocephala (Lam.) De Wit.), sobre a germinacao e o desenvolvimento das plantas de milho (Zea mays L.). Os extratos foram preparados na concentracao 20% (p/v), e avaliados em solo e papel- germiteste, em casa de vegetacao, e em papel-filtro em laboratorio. O extrato obtido com agua fria (EF) e aplicado ao solo nao causou nenhum efeito fitotoxico sobre a germinacao e o desenvolvimento das plantas de milho. O extrato obtido com agua quente (EQ), quando aplicado em papel-germiteste ou papel-filtro, causou reducao no comprimento da raiz seminal, mas nao interferiu na germinacao das sementes de milho. O comprimento da raiz seminal foi um indicador mais sensivel aos efeitos do EQ do que a germinacao.

Evolvimento de dióxido de carbono e mineralização de nitrogênio em Latossolo Vermelho-Escuro com diferentes manejos

The objective of this work was to verify the influence of different types of straw (maize and lablab) and soil management on evolving CO2 and N mineralization. A dystrophic clayey Dark-Red Latosol under Cerrado from the region of Sete Lagoas, MG, Brazil, was cultivated during five years with no-tillage, disc-plow and moldboard-plow. Soil samples (0-20 cm) were incubated at 25oC during 55 days, with and without N fertilizer applied at the beginning and 25 days afterwards. As a general rule, the maize straw had higher rates of evolved CO2 than the lablab (935 e 764 mg CO2 g-1 soil, respectively). The type of straw influenced the amount of CO2 evolved more than the type of soil management did. Nitrogen addition increases the rate of CO2 evolved only when applied at the beginning of the incubation period. The N availability and the duration of the immobilization are modified by the C/N ratio and by the type of soil management.

BRSMG Madrepérola: common bean cultivar with late-darkening Carioca grain

The cultivar BRSMG Madreperola, recommended for cultivation in Minas Gerais, has the feature of maintaining a light grain color for a longer period than other Carioca grain cultivars. The yield potential is high and the resistance level good to the major anthracnose races in the region.

Sistema de plantio de milho em fileiras duplas e simples em consórcio com o feijoeiro comum

The objective of this work was to identify sowing systems that allow the best condition of common bean yield in intercropping with maize sowed in double and single lines. The trials were carried out at Embrapa-Centro Nacional de Pesquisa de Milho e Sorgo (CNPMS), Minas Gerais State, Brazil, in 1988/89 and 1989/90. The maize cultivars BR 201, Cargill 606 and CMS 350 were sowed in double rows with 50 cm within the pair of double rows, and 150 cm between the pair of double rows at 40,000 and 60,000 plants per hectare. The check was 100 cm single row with 40,000 plants per hectare. Planting density of common beans was 120,000 plants per hectare, which was constant in the systems. Differences were not observed for maize yield between planting systems. Common bean yield decreased when intercropped with maize Cargill 606 and CMS 350 in double lines. The hybrid Cargill 606 in single line increased the yield of the legume. The cultivar BR 201 was the most efficient for intercropping because of higher grain yield average and also because it allowed good average yields of common beans. The planting systems and the climate exerted influence on the grain yields.

Green ear yield and grain yield of maize after harvest of the first ear as baby corn

Baby corn (BC) consists of the corn ear harvested two or three days after silk emergence. BC is a profitable crop, making possible a diversification of production, aggregation of value and increased income. Removing the first female inflorescence induces corn to produce others, making possible to produce several BC ears or, alternatively, BC (by harvesting the first ear) and green ears or grain. The objective of this work was to evaluate green ear yield and grain yield, after harvesting the first ear as BC. Corn cultivar AG 1051 was submitted to the following treatments, in a random block design with ten replicates (52 plants per plot): BC harvesting; green ear harvesting (grain moisture content between 60 and 70%); mature ear harvesting; BC harvesting and harvesting of other ears as green or mature ears. Marketable green ears yield or grain yield produced without removing the first inflorescence were superior to the green ears yield or grain yield produced after removal of the first inflorescence harvested as baby corn. Harvesting only the first ear as baby corn, and then harvesting green ears or the mature ears, provided lower baby corn yields than that obtained by harvesting all ears as baby corn. Economically, the best net revenues would be obtained by exploring the crop for the production of green ears, green ears + baby corn, baby corn, baby corn + grain, and grain, in this order.

CONTROLE DE PLANTAS DANINHAS NA CULTURA DO MILHO UTILIZANDO LEUCENA (Leucaena leucocephala (LAM.) DE WIT)

Com o objetivo de verificar se a posicao da semente na espiga afeta diferentemente a produtividade e outros caracteres da planta e se essa diferenca pode ser ampliada por meio de ciclos seletivos, foi conduzido o presente trabalho. Para isto, na safra 1995/1996, foram semeadas, em lote isolado, cerca de 3.000 plantas da populacao CMS-39 e, por ocasiao da colheita, tomadas 300 espigas ao acaso. De cada espiga, foram coletadas sementes das extremidades e, posteriormente, as sementes da ponta de cada espiga foram misturadas e o mesmo foi realizado com as sementes da base. Esse procedimento foi repetido de modo analogo por cinco ciclos seletivos. As dez subpopulacoes, cinco da ponta e cinco da base, foram avaliadas em experimentos conduzidos nas safras 2000/2001 e 2001/2002. O delineamento utilizado foi o de blocos casualizados, com seis repeticoes, segundo esquema de parcelas subdivididas. Os tratamentos nas parcelas foram os cinco ciclos seletivos e, nas subparcelas, a origem das sementes, ponta ou base. Foram considerados os caracteres numero de dias para o florescimento masculino e feminino, altura de espiga e produtividade de graos. Constatou-se que a origem da semente da ponta ou da base nao alterou a expressao de varios caracteres avaliados e nao foi possivel, com a precisao experimental obtida, detectar efeito da selecao indireta para o vigor de polen pela posicao dos graos na espiga, em todos os caracteres considerados.

BRSMG União: common bean cultivar with jalo grain for the state of Minas Gerais

The bean cultivar BRSMG Uniao as a new option of a bean cultivar with jalo grains for the state of Minas Gerais. The cultivar BRSMG Uniao had an average grain yield of 9.8% above the mean of the controls (Jalo EEP 558 and BRS Radiante) and was resistant to powdery-mildew.

Corn and common bean intercropping-system with double and simple corn rows

The objective of this work was to identify sowing systems that allow the best condition of common bean yield in intercropping with maize sowed in double and single lines. The trials were carried out at Embrapa-Centro Nacional de Pesquisa de Milho e Sorgo (CNPMS), Minas Gerais State, Brazil, in 1988/89 and 1989/90. The maize cultivars BR 201, Cargill 606 and CMS 350 were sowed in double rows with 50 cm within the pair of double rows, and 150 cm between the pair of double rows at 40,000 and 60,000 plants per hectare. The check was 100 cm single row with 40,000 plants per hectare. Planting density of common beans was 120,000 plants per hectare, which was constant in the systems. Differences were not observed for maize yield between planting systems. Common bean yield decreased when intercropped with maize Cargill 606 and CMS 350 in double lines. The hybrid Cargill 606 in single line increased the yield of the legume. The cultivar BR 201 was the most efficient for intercropping because of higher grain yield average and also because it allowed good average yields of common beans. The planting systems and the climate exerted influence on the grain yields.

DESEMPENHO DE LINHAGENS ELITE DE FEIJÃO-CAUPI EM AMBIENTES DE MINAS GERAIS E MATO GROSSO

The objective of this work was to evaluate the agronomic performance of erect and semi-erect cowpea elite lines grown in the States of Minas Gerais and Mato Grosso, Brazil. The experiments were conducted in Jaíba, Janaúba, Sete Lagoas (Minas Gerais), Primavera do Leste and Nova Ubiratã (Mato Grosso), with 20 genotypes of cowpea, arranged in a randomized block design with four replications. The data were subjected to individual and joint analyses of variance and means grouped by the Scott-Knott test (p<0.05). The plant growth habit, lodging, cultivation value, pod length and bean yield were evaluated. The lines MNC04768F-21 and MNC04F-795F-168 had the highest bean yield in the experiments conducted in Mato Grosso, and their growth habit, lodging and cultivation value were similar to those of the cultivar BRS-Guariba. The lines MNC04-769F-30, MNC05-795F-154 and MNC04-769F-49 and the cultivar BRS-Tumucumaque had the highest bean yield in the experiments conducted in Minas Gerais. However, the cultivars BRS-Guariba, BRSTumucumaque, BRS-Novaera, BRS-Itaim and BRS-Cauamé and the lines MNC04-792F-143 and MNC04792F-144 showed satisfactory bean yield and good growth habit, plant lodging and cultivation value in the State of Minas Gerais, especially in the northern region of the state (Jaíba and Janaúba), representing good alternatives for the genotypes recommended for this region.