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Borges P.H.M.,UFMT Cuiaba MT | Bianchini A.,UFMT Cuiaba MT | Maia J.C.S.,UFMT Cuiaba MT | Fernandes H.C.,UFV Vicosa MG | Mendoza Z.M.S.H.,UFMT Cuiaba MT
Engenharia Agricola | Year: 2014

In this study, empirical models were developed to determine the tensile force demanded by disc plows, harrows and planters fertilizers, as function of soil mechanical resistance to penetration. The mean of the referred resistance was determined until 25, 35 and 15 cm depths, according to the regulations for the disc plow, springs harrow and fertilizer seeder. The adjustment was verified based on the coefficient of determination, dispersion graphics, residual analysis and t test (Student). It was confirm the normality of the residuals and to establish intervals of confidence with 95% of probability. The estimated and experimentally obtained values did not differ significantly. It was concluded that the associated exponential functions presented appropriate precision and reliability to predict the traction force being considered the soil mechanical resistance to penetration and that the models can be a useful tool for planning and management of mechanized farming operations in soils with texture similar to those of this research. Source

Elesbon A.A.A.,IFES Colatina ES | da Silva D.D.,UFV Vicosa MG | Sediyama G.C.,UFV Vicosa MG | Guedes H.A.S.,Curso de Engineering Civil | And 2 more authors.
Engenharia Agricola | Year: 2015

This study aimed to develop a methodology based on multivariate statistical analysis of principal components and cluster analysis, in order to identify the most representative variables in studies of minimum streamflow regionalization, and to optimize the identification of the hydrologically homogeneous regions for the Doce river basin. Ten variables were used, referring to the river basin climatic and morphometric characteristics. These variables were individualized for each of the 61 gauging stations. Three dependent variables that are indicative of minimum streamflow (Q7,10, Q90 and Q95). And seven independent variables that concern to climatic and morphometric characteristics of the basin (total annual rainfall - Pa; total semiannual rainfall of the dry and of the rainy season - Pss and Psc; watershed drainage area - Ad; length of the main river - Lp; total length of the rivers - Lt; and average watershed slope - SL). The results of the principal component analysis pointed out that the variable SL was the least representative for the study, and so it was discarded. The most representative independent variables were Ad and Psc. The best divisions of hydrologically homogeneous regions for the three studied flow characteristics were obtained using the Mahalanobis similarity matrix and the complete linkage clustering method. The cluster analysis enabled the identification of four hydrologically homogeneous regions in the Doce river basin. Source

Pruski F.F.,UFV Vicosa MG | Rodriguez R.D.G.,UFV Vicosa MG | Nunes A.A.,UFV Vicosa MG | Pruski P.L.,UFV Vicosa MG | Singh V.P.,Texas A&M University
Engenharia Agricola | Year: 2015

Knowledge of natural water availability, which is characterized by low flows, is essential for planning and management of water resources. One of the most widely used hydrological techniques to determine streamflow is regionalization, but the extrapolation of regionalization equations beyond the limits of sample data is not recommended. This paper proposes a new method for reducing overestimation errors associated with the extrapolation of regionalization equations for low flows. The method is based on the use of a threshold value for the maximum specific low flow discharge estimated at the gauging sites that are used in the regionalization. When a specific low flow, which has been estimated using the regionalization equation, exceeds the threshold value, the low flow can be obtained by multiplying the drainage area by the threshold value. This restriction imposes a physical limit to the low flow, which reduces the error of overestimating flows in regions of extrapolation. A case study was done in the Urucuia river basin, in Brazil, and the results showed the regionalization equation to perform positively in reducing the risk of extrapolation. Source

Pereira M.S.,UFV Vicosa MG | Matos A.T.,Federal University of Minas Gerais | Borges A.C.,UFV Vicosa MG | Nunes M.F.,UFV Vicosa MG
Engenharia Agricola | Year: 2015

The objective of this study was to evaluate organic carbon (OC) and organic nitrogen (ON) decomposition in peach palm waste under field and laboratory conditions. Application was performed by both incorporating and releasing the waste onto soil surface. Field experiment was carried out on an Inceptisol under tropical conditions during the spring and summer seasons in Viçosa - MG, Brazil. The waste was incubated under field and laboratory conditions for 112 days within which samples were taken for analysis. We noted that waste was more intensely degraded under field conditions than in lab environment. Moreover, waste incorporation into soil accelerated the degradation under both incubation conditions. The estimation methods for coefficients and fractions of OC mineralization, inorganic nitrogen availability under lab condition produced results consistent with field ones; however, they were considerably underestimated. Source

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