Rubens Alves de Oliveira

Efeito da irrigação e adubação na disponibilidade e composição bromatológica da massa seca de lâminas foliares de capim-elefante

An experiment was carried out to evaluate the effect of irrigation, followed by increasing levels of nitrogen and potassium (100-80; 200-160; 300-240; 400-320, respectively N and K2O), on the production and chemical composition of the leaf lamina at the elephantgrass. The experimental delineation was of blocks randomized with three repetitions for treatments irrigated and dry land. The low temperatures and the smallest light hours in the dry season determined the low plant forage growth, even with the irrigation. However, in the summer, there was fast growth of plant forage under irrigation, emphasizing the culm growth in relation to leaf laminas, determining the lower relations to the higher fertilizer levels. The leaf laminas under irrigation also showed the lower crude protein contents and higher NDF and ADF contents. So, more frequent managing in the irrigated pastures could control the culm growth and available material of better chemical composition.

Disponibilidade de matéria seca em pastagens de capim-elefante irrigadas

Com o objetivo de avaliar os efeitos da irrigacao na disponibilidade de materia seca em pastagens de capim-elefante, cv. Napier, foi conduzido um experimento durante dois anos no Setor de Agrostologia da UFV. A irrigacao foi realizada por um sistema de aspersao convencional de media pressao, usando turno de rega variavel. Observou-se que, nos dois periodos de seca abrangidos pelo experimento, a irrigacao nao conseguiu determinar diferencas significativas na disponibilidade de materia seca do capim-elefante. Por outro lado, quando se avaliaram os resultados acumulados para os periodos de inverno e verao, a disponibilidade de forragem nos tratamentos sob irrigacao foi sempre significativamente maior, em razao de a irrigacao suprir e manter a umidade do solo em niveis suficientemente adequados para as forrageiras, quando as temperaturas minimas nao foram limitantes ao crescimento, eliminando os efeitos dos veranicos e permitindo manutencao da estabilidade da producao. Conclui-se que a irrigacao realizada de forma eficiente e criteriosa pode ser mais uma alternativa, visando ao aumento da producao animal a pasto, pois permite significativos aumentos na producao forrageira, principalmente no verao, quando as temperaturas minimas nao foram limitantes ao desenvolvimento do capim-elefante.

Influência da competição catiônica nos valores de fator de retardamento e coeficiente de dispersão-difusão de zinco e cobre no solo

The effects of the cationic competition on the retarding factor (fr) and the dispersion-diffusion coefficient (D) were evaluated with conducting metal mobility trials in leaching columns submitted to a saturated and steady flow. Solutions of zinc (700 mg L-1), copper (200 mg L-1) and zinc plus copper in the same concentrations, were used to obtain elution curves. Soil materials from the A, B and C horizons of Oxisol (LVa) and of Ultisol (PVc), collected in Vicosa, MG, were used. In all soil materials used, copper presented higher retarding factor values than zinc, which indicates a higher copper-soil interaction. The low velocities of the solutions resulted in low dispersion-diffusion coefficient values. Cationic competition decreased the soil retention capacity for the cations.

Nitrogen fertilization strategies for xaraes and tifton 85 grasses irrigated in the dry season

An experiment was carried out to assess rates and nitrogen fertilization strategies on the forage yield using irrigation to supply the water deficit during the dry season. The grasses Cynodon spp cv. tifton 85 and Brachiaria brizantha cv. Xaraes were cultivated with nitrogen (N) at levels of 200 and 400 kg/ha according to strategies: 1) half dose applied during the rainy season (RS) and half during the dry season (DS); 2) 1/3 during the RS and 2/3 during the DS; 3) 2/3 during the RS and 1/3 during the DS; 4) all doses applied during the DS. In each season the dose was divided in three applications. Eleven harvests were conducted: six in the RS and five in the DS. When 2/3 of N was applied in the DS, forage yield in this period was statistically equivalent to those obtained in the RS in three of the five harvests for both 200 and 400 kg/ha of N. With 100% of N applied in the DS, the yield of four of five cuts of forage was similar to that obtained in the RS for both rates of N. The strategy of applying more N in the DS rather than in the RS was effective, keeping the yield steadily throughout the year. The application of 100% of the dose of 200 kg/ha N and 2/3 of the dose of 400 kg/ha N both in the dry period, under irrigation, promote uniform productions per harvest throughout the year.

Estudo comparativo de métodos para estimativa do carregamento e rendimento de motores elétricos para auditoria energética

Este artigo investiga a precisao de tres metodos indiretos para a determinacao do indice de carregamento e rendimento de motores eletricos. Determinou-se o erro da estimativa do indice de carregamento e rendimento de motores eletricos pela media aritmetica e geometrica das correntes e pela media aritmetica dos fatores de potencia. Mostrou-se, tambem, a importância da determinacao do decrescimo do rendimento de motores eletricos, decorrente da variacao de tensao da rede eletrica. Verificou-se que a estimativa do indice de carregamento e do rendimento dos motores eletricos por meio da medicao do fator de potencia medio aritmetico apresentou resultados com maiores erros percentuais, 24,5% e 2%, respectivamente; ja estas estimativas apresentaram, pelos metodos da corrente media aritmetica e media geometrica, resultados semelhantes entre si e com erros percentuais significativamente inferiores aos resultados anteriores, ou seja, 6,2% e 1%, respectivamente.

Vazão de gotejadores com distintos tempos de irrigação aplicando água residuária de suinocultura e água de abastecimento

This study aimed to analyze the effect of the proportion of time irrigation with swine wastewater (ARS) and supply water (AA) on alteration of drippers flow rate. The experiment was set up on split-split-plot scheme with proportions of irrigation time of ARS and AA (1E3A - 1 h of ARS and 3 h of AA, 2E2A - 2 h of ARS and 2 h of AA, 3E1A - 3 h of ARS and 1 h of AA and 4E - 4 h of ARS) in the plot, kind drippers (G1, G2 and G3) in the subplots and the operation time (0, 20, 40, 60, 80, 100, 120, 140 and 160 h) in the sub-subplots on an entirely randomized design, with three replicates. The physico-chemical and biological characteristics of ARS and AA were obtained every 20 h and 80 h, respectively. The flow rate was determined in 22 drippers of each lateral line, also, every 20 h. After 160 h, drippers and lateral line were dissected to investigate the material of obstruction. The combination of drippers G1 and G3 with the proportions of irrigation time 1E3A and 4E minimized clogging process, where the reduction on flow rate values were of 16 and 8%, respectively, after 160 h of operation of the irrigation units.

Perda de carga em tubulação de polietileno, conduzindo água residuária de suinocultura

The objective of this work was to adjust equations to calculate continuous head loss in polyethylene pipelines carrying swine wastewater with concentrations of 1.15; 1.24; 1.43 and 1.75 g L-1 of total solids. The head loss was determined in polyethylene pipelines, with internal diameters of 12.62; 15.47; 19.79 and 25.76 mm, by means of four piezometers, 4 m apart along the pipelines. The results indicated that the empirical equations adjusted with the methodologies of Duffy & Titchener and Hazen-Williams modified gave good results with coefficient of determination equivalent to 0.99, therefore, its application is recommended to design of projects with polyethylene pipelines.

Influence of swine wastewater application on the infiltration capacity of a red-yellow podzolic soil.

This work was carried out at the Experimental Area of Hydraulics, Irrigation and Drainage of the Agricultural Engineering Department, at the Federal University of Vicosa, Vicosa, Minas Gerais, Brazil. The aim was to evaluate the influence of successive applications of swine wastewater, with different concentrations of total solids, on the infiltration capacity of a Yellow Red Podzol. The experiment was conducted in a completely randomized design with five treatments and three replications. The treatments consisted of applying water and swine wastewater with 2.4, 7.0, 16.3 and 26.9 g L-1 of total solid concentrations. Fifteen ring infiltrometers were installed in an area of 60 m2, which was divided in plots of 2 x 2 m dimensions. Four infiltration tests were performed at 15 day intervals in each plot. It was concluded that increasing the total solid concentration of swine wastewater caused a reduction of the soil infiltration capacity. In addition, it was observed that successive applications intensified this effect. The total solid concentration of wastewater was more important to reduce the soil infiltration capacity than the levels of sodium absorption ratio and salinity.