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Sete Lagoas, Brazil

Leite F.P.,Celulose Nipo Brasileira S.A. CENIBRA | Silva I.R.,Federal University of Vicosa | Novais R.F.,Federal University of Vicosa | de Barros N.F.,Federal University of Vicosa | And 2 more authors.
Revista Brasileira de Ciencia do Solo | Year: 2011

To synchronize nutrient availability with the requirements of eucalyptus during a cultivation cycle, the nutrient flow of this system must be well understood. Essential, for example, is information about nutrient dynamics in eucalyptus plantations throughout a cultivation cycle, as well as impacts on soil nutrient reserves caused by the accumulation and subsequent export of nutrients via biomass. It is also important to quantify the effect of some management practices, such as tree population density (PD) on these fluxes. Some nutrient relations in an experiment with Eucalyptus grandis, grown at different PDs in Santa Barbara, state of Minas Gerais, Brazil, were evaluated for one cultivation cycle. At forest ages of 0.25, 2.5, 4.5, and 6.75 years, evaluations were carried out in the stands at seven different PDs (between 500 and 5,000 trees ha-1) which consisted in chemical analyses of plant tissue sampled from components of the aboveground parts of the tree, from the forest floor and the litterfall. Nutrient contents and allocations of the different biomass components were estimated. In general, there were only small and statistically insignificant effects of PD on the nutrient concentration in trees. With increasing forest age, P, K, Ca and Mg concentrations were reduced in the aboveground components and the forest floor. The magnitud of biochemical nutrient cycling followed the sequence: P > K > N > Mg. At the end of the cycle, the quantities of N, P, Ca and Mg immobilized in the forest floor were higher than in the other components.

Oliveira E.L.,FAPEMIG | Faria M.A.,Campus Universitario | Evangelista A.W.P.,Federal University of Goais | Melo P.C.,Federal University of Lavras
Revista Brasileira de Engenharia Agricola e Ambiental | Year: 2012

Jatropha curcas crop is raising attention as an alternative crop for biodiesel production. Despite the irrigation and mineral fertilization to promote increase of Jatropha curcas yield, few studies have been conducted on this issue. The purpose of this work was to evaluate the growth and productivity of Jatropha curcas, in response to irrigation management and potassium fertilization doses. The field experiment was carried out at the Federal University of Lavras in the southern part of the State of Minas Gerais. Four different irrigation depths, corresponding to different fractions (0, 40, 80, 120%) of the Class A pan evaporation (ECA), and four potassium doses (30, 60, 90 and 120 kg ha-1 of K2O) were used as treatments. To evaluate the growth and yield of Jatropha curcas seeds the data corresponding to first and second year of cultivation was used. The results showed that plants irrigated showed better productivity and initial growth, while potassium fertilization levels did not show significant effect.

Todeschini G.,Worcester Polytechnic Institute | McNeill J.,Worcester Polytechnic Institute | Emanuel A.,Worcester Polytechnic Institute | Policarpo J.,FAPEMIG
2010 IEEE Conference on Innovative Technologies for an Efficient and Reliable Electricity Supply, CITRES 2010 | Year: 2010

This paper presents a preliminary study meant to determine the economic feasibility of partially using distributed generators (DGs) as active filters (AFs) meant to sink current harmonics injected by nonlinear loads (NLs) connected at the same feeder as the DG. Such approach may avoid the installation of dedicated AFs, nevertheless it may cause exceeding thermal stressing of insulation and solid state switches. ©2010 IEEE.

Queiroz D.S.,Epamig | Casagrande D.R.,Federal University of Vicosa | Moura G.S.,FAPEMIG | Silva E.A.,Epamig | And 2 more authors.
Revista Brasileira de Zootecnia | Year: 2012

The objective of this study was to evaluate the forage availability, pasture morphological and chemical composition, pasture carrying capacity and the milk production of cows on three forage grasses under continues stocking and the variable rate on lowland soil. The experimental design was completely randomized with three treatments and three replicates. The treatments were the Paspalum atratum cv Pojuca grass, Brachiaria humidicola cv Llanero grass and tangola grass (natural hybrid of Brachiaria arrecta and Brachiaria mutica). The stocking rate was adjusted to maintain the forage available between 2.000 and 3.000 kg dry matter per hectare. The period evaluated was from November 2003 to May 2004. There was no significant difference between the species when the dry matter availability of green forage was evaluated, with mean value of 2.902 kg/ha. The pojuca grass had 62% of leaf blade and 38% of stem + sheath in green forage dry mass, followed by humidícola grass with 49 and 51% and tangola grass with 18 and 22%, respectively. The tangola grass showed higher level of crude protein on the leaf blade (15.41%) than humidícola (9.98%) and pojuca (8.74%) grasses and lower levels of fiber (NDF and ADF). The individual production of cows was affected by the better nutritional value of the tangola grass. The average daily production of this grass was higher (10.27 kg/cow) than the pojuca grass (7.8 kg/cow) and had similar value to humidícola grass (9.16 kg/cow). The milk production per area, with had mean of 27.8 kg/ha × day-1, was not affected by the forage grasses because the more high stocking rate of pojuca grass, although not significant, compensated the lower individual production. © 2012 Sociedade Brasileira de Zootecnia.

Changes in the pH of the rhizosphere of N2-fixing plants seem to play a key role in the uptake of micronutrient whose availability depends on changes in soil acidity. Variations in the B, Cu, Fe, Mn, and Zn uptake were studied during soybean development and growth cycle under the influence of biological N2 fixation and the initial pH of two soils samples (a clayey and a sandy Yellow atosol; Oxisols), in a greenhouse xperiment. These samples were incubated with rates of CaCO3 + MgCO3 (4:1) to raise the pH (H2O) to 5.2, 5.6, 6.2, and 6.6 in the clay soil and to 5.3, 5.6, 5.9, and 6.3, respectively, in the sandy soil. After 60 days of incubation, the soil samples were fertilized with 450 mg dm-3 P and 120 mg dm-3 K. Soybean (Glycine max (L) Merrill) seeds of the variety Paranaíba, inoculated with the strains SEMIA 587 and SEMIA 5019 of Bradyrhizobium japonicum were germinated. Four plants per pot (2.2 dm3) were grown and harvested 16, 20, 24, 28, 32, 36, 40, 46, and 54 days after emergence. The following variables were measured: pH of the rhizosphere (pHr), the non-rhizospheric soil pH (between roots) (pHnr), the B, Cu, Fe, Mn and Zn contents in shoots and roots, N in the shoot, number of nodules, and the shoot, root and nodule dry matter. It was observed that changes in pHr and pHnr depended on the initial soil pH (pHs) and on biological N2 fixation. The accumulation of B and Fe in the shoots was not influenced by the pHr values modified depending on the pH, except for Fe in the clay soil. However, nodules appeared 24 days after emergence and nutrient accumulation was significantly increased from then on. For Cu, Mn and Zn uptake seemed to be affected mainly by pHr. The micronutrient content in the plants proved to be sensitive to changes in the rhizospheric pH, particularly after nodulation.

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