935 resultados para Subsistema de Cerrado
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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O nitrogênio é o nutriente mais exigido pelo feijoeiro e seu metabolismo pode ser seriamente prejudicado pela deficiência de molibdênio. Conduziu-se este trabalho, com o objetivo de avaliar o efeito da aplicação de molibdênio via semente e nitrogênio em cobertura nas características agronômicas e produtividade do feijoeiro 'BRS Pontal' irrigado, cultivado em Neossolo Quartzarênico, no município de Cassilândia, MS. O delineamento experimental utilizado foi o de blocos casualizados, no esquema fatorial 4x2, com quatro repetições. Os tratamentos foram constituídos pela aplicação ou não de Mo (80 g ha-1) via semente e quatro doses de N (0, 30, 60 e 120 kg ha-1), em cobertura aos 16 dias, após a emergência, na forma de uréia. A aplicação de Mo via semente aumentou o índice relativo de clorofila, o número de vagens por planta, a massa e a produtividade de grãos no feijoeiro, principalmente com o uso de altas doses de N em cobertura. O índice relativo de clorofila, o número de vagens por planta, a massa e a produtividade de grãos do feijoeiro foi aumentada linearmente pela aplicação de até 120 kg ha-1 de N em cobertura. O fornecimento de Mo via tratamento de semente aumentou a eficiência de utilização do N pelo feijoeiro.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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In this work it was demanded to verify the zinc critical levels in soybean plants cultivated in a Dark-Red Latosol. So the experiment was carried out in vases with 4 liters of soil, which has received five doses of Zn (0, 1.0, 2.0, 3.0 and 4.0 ppm) in three correction levels. It was verified that the critical levels of the nutrient in plant (for 90% from highest production) was between 36 and 53 ppm to the dry matter yield and grains in treatments with correction.
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The purpose of this work was to assess the effects of soil preparation methods (with or without subsoiling) on physical properties of a cerrado soil cropped to corn during the, 1986/87 season, in the Selviria county (Mato Grosso do Sul, Brazil). Also, the objective of this was to check the changes in the soil (dark red latosol-Acrustox) caused by the preparation after nine years of cultivation in comparison with natural state. The experiment consisted of six soil preparation systems: conventional, superpreparation, reversed, revolving hoe, reduced and no-tillage. Along with these systems subsoiling was also tested. The reversed system showed the best com grain yield. Subsoiling only presented positive results in productivity with the no-tillage system. All the preparation system tested degraded the physical properties in comparison with the natural soil.
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In the Cerrado savannas from Brazil fire events are common and strongly influence the vegetation structure and, consequently, the associated small mammals. In this paper, we investigate changes in the structure of small mammal communities related to sites of different post-fire ages. Mammals were captured in similar Cerrado sites that differed in time since the last burn ( 1 to 26 yr). We sampled six sites in the wet season of 1997 ( phase 1) and, three years later, six sites in the wet and dry seasons ( phase 2). Six rodent species and four marsupials were captured. Community composition changed drastically as a function of time since fire. The diversity and abundance of small mammals reached maximum values in the early successional stages. The rodent Calomys tener was present only in early seral stages. The rodent Bolomys lasiurus was more frequent in mid-successional stages and decreased in later seral stages, and the rodent Oryzomys subflavus occupied all successional stages. The marsupial Gracilinanus agilis was dominant in the area that did not burn for at least 23 yr. Changes in composition of the community of small mammals were more accelerated in early successional stages, when there are more drastic vegetational changes. The ability of small mammals to cope with Cerrado fires and the great dissimilarity among post-burning seral stages suggest that a mosaic of areas representing different post-fire seral stages could increase the regional diversity of this group.
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The basic knowledge of the seasonal occurrence of mites can supply data for elaboration of programs of ecological management to be implanted with success in the future. The objective of this study was to determine the species richness and the seasonality of mites present in two areas of rubber tree crops neighboring to native areas in Itiquira, MT. Along one year, 25 quantitative samplings were accomplished in rubber tree crop neighboring to two fragments of Cerrado (Cerradao and Mata Riparia). There were registered 199,380 mites, of 48 species, belonging to 15 families. of those, 13 species are phytophagous, 18 predators and 17 mycophagous or of unknown alimentary habit. Three phytophagous species represented more than 97% of the mites collected: Phyllocoptruta seringueirae Feres (80.8%), Tenuipalpus heveae Baker (12.7%) and Calacarus heveae Feres (3.6%). Among the predators, the most abundant species were Agistemus sp., Scirula sp. and Euseius concordis (Chant). Twenty-eight species were common to both crops. The families that had the largest number of species collected in the neighboring area to Cerradao were Tydeidae (7), Tarsonemidae (6), Eriophyidae and Phytoseiidae (4), and in the area close to Mata Riparia, Tydeidae (9) and Phytoseiidae (8). The presence of vegetation near the crop should explain the great number of species of mites classified as accidental found in this study. The largest abundances and species richness occurred in the end of the rainy season and beginning of the dry season.
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Based on the results of a phytosociological survey in a ''cerrado'' area located within the municipality of Botucatu, state of São Paulo Brazil, a comparative analysis of the 58 sampled tree species' is here presented using the data of other available floristics works for the ''cerrados in the same state. With a binary matrix of presence/absence of shared common species with the studied plot, a clustering analysis was performed thus obtaining a dendrogram which groups northern and southern areas with the same vegetation in the state of São Paulo previously treated as floristicaly differentiated. These results are discussed under the assumption that Isolated areas of ''cerrados'' are to be taken as targets for immediate conservation.
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Several changes in the soil humus characteristics were observed after clearing the Central Brazil virgin forest. When compared with the original ''Cerrado'' forest, the soils from the agricultural systems showed increased values for cation exchange capacity, total organic matter and non-extractable humin. The humic acid fraction underwent some changes suggesting increased oxidation and decreased aliphatic content. The soil organic N tends to accumulate in the insoluble humus fractions.The above changes were much less intense when the virgin forest was transformed into pastures. Under these conditions, the most significant changes were the reduction of readily biodegradable soil organic matter fractions.In view of the intensity of the lixiviation processes in the area studied, the above changes may be connected with the reduction in aggregate stability observed in the cleared sites.In general, the characteristics of the humus formations in the ''Cerrado'' region suggested high resistance to external factors, which is in part attributed to the active insolubilization of humic colloids by the Al and Fe oxides. In the absence of erosive processes in the cleared sites, additional humus stability may conform both to selective biodegradation and/or lixiviation of the humic colloids, or to the effects of the fire used in soil management.