990 resultados para soil texture


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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Pós-graduação em Agronomia (Energia na Agricultura) - FCA

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Pós-graduação em Ciências Biológicas (Biologia Vegetal) - IBRC

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Pós-graduação em Agronomia (Energia na Agricultura) - FCA

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Pós-graduação em Geociências e Meio Ambiente - IGCE

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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This work was based on a complete tree stem analysis to assess the growth behavior and current annual volume increment (CAI) of four individuals of Pinus taeda sampled in populations located in the 'Avare II' State Forest and 'Itapeva' Experimental Station, State of São Paulo. The relationship between the rainfall time series and CAI index was examined by means of cross-correlation coefficients. The convergence coefficients (GL) between the series were calculated. In the individuals that showed a statistical significance in the cross-correlation between the time series, the previous year's rainfall significantly affected the current annual volume increment in the year under consideration. The GL values between the series were higher in 'Itapeva'. Since the two sites showed no significant difference in rainfall distribution, the difference was attributed to the soil texture at 40-60 cm - medium in 'Avare' and clayey in 'Itapeva', so the CAI of the 'Itapeva' plantation reflects the higher availability of water.

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Although many studies have shown that soil solution chemistry can be a reliable indicator of biogeochemical cycling in forest ecosystems, the effects of litter manipulations on the fluxes of dissolved elements in gravitational soil solutions have rarely been investigated. We estimated the fluxes of NH4-N, NO3-N, K, Ca, Mg, Na, Cl, dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) over the first two years after re-planting Eucalyptus trees in the coastal area of Congo. Two treatments were replicated in two blocks after clear-cutting 7-year-old stands: in treatment R, all the litter above the mineral soil was removed before planting, and in a double slash (DS) treatment, the amount of harvest residues was doubled. The soil solutions were sampled down to a depth of 4 m and the water fluxes were estimated using the Hydrus 1D model parameterized from soil moisture measurements in 4 plots. Isotopic and spectroscopic analytical techniques were used to assess the changes in dissolved organic matter (DOM) properties throughout the transfer in the soil. The first year after planting, the fluxes of NH4-N, K, Ca, Mg, Na, Cl and DOC in the topsoil of the DS treatment were 2-5 times higher than in R, which showed that litter was a major source of dissolved nutrients. Nutrient fluxes in gravitational solutions decreased sharply in the second year after planting, irrespective of the soil depth, as a result of intense nutrient uptake by Eucalyptus trees. Losses of dissolved nutrients were noticeably low in these Eucalyptus plantations despite a low cation exchange capacity, a coarse soil texture and large amounts of harvest residues left on-site at the clear cut in the DS treatment. All together, these results clarified the strong effect of litter manipulation observed on eucalypt growth in Congolese sandy soils. DOM fluxes, as well as changes in delta C-13, C:N and aromaticity of DOM throughout the soil profile showed that the organic compounds produced in the litter layer were mainly consumed by microorganisms or retained in the topsoil. Below a depth of 15 cm, most of the DOC and the DON originated from the first 2 cm of the soil and the exchanges between soil solutions and soil organic matter were low. (C) 2014 Elsevier B.V. All rights reserved.

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Pós-graduação em Agronomia (Energia na Agricultura) - FCA

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The increased use of herbicides, coupled with inadequate use of these molecules, also increased concerns about the risks of environmental contamination and its effects on humans and animals. The objective of this work evaluates the potential for leaching of herbicides in the crop of cane sugar, in contrasting soils. Used samples were used Psament (NR - sandy texture) and Oxisol Red (LR - clay texture). After application of herbicides ametryne (NR 1.60 kg ha(-1) and LR 2.40 kg ha(-1)), clomazone (NR 0.90 kg ha(-1) and LR 1.10 kg ha(-1)) and diuron (NR 1.60 kg ha(-1) and LR 3.20 kg ha(-1)), were irrigated blades of 0, 20, 40, 60, 80 and 100 mm of water in soil columns. Results indicate that ametryne in NR samples submitted to the handling layer of 5-10 cm when applied blades of 20 and 40 mm of water. It was evident that the clomazone, regardless of the soil, did not exceed 0-5 cm water depths of 0 to 20 mm of water and 5-10 cm deep in the blades above 40 mm of water. With blades up to 80 mm, the diuron leaching only in layers 0-5 cm deep in LR. Conclude that the potential of leaching of diuron and ametryne was influenced by soil texture together with the organic matter content, the same was not true for clomazone.