E. O. Brandão

Variação do balanço de radiação e de energia da cana-de-açúcar irrigada no semiárido brasileiro

The objective of this work was to analyze the variations in the magnitudes and partition of the radiation and energy balance components, obtained during the growth period of the irrigated sugarcane (variety RB92579). The experiment was carried out in Juazeiro-BA, located in the Brazilian semiarid region. The sensible (H) and the latent (LE) heat fluxes in the air were estimated by means of the Bowen ratio energy balance (BREB). The crop growth was also monitored. In a preliminary analysis of this method, it was verified that 62.7% of the collected data presented physical consistence to be used for estimating the H and LE components. It was observed that the mean value of the Rn/Rg ratio was equal to 59±5%, with smaller values occurring at the beginning and at the end of sugarcane crop cycle, while the magnitude of long wave radiation balance (BOL) was intensified when the leaf area index (LAI) was reduced. Also, it was noticed that the mean value of the albedo was 23±3% and that 81% of the available energy was destined to the latent heat flux, while the sensible heat in the air (H) and in the soil (G) represented 16 and 3%, respectively.

Acúmulo e exportação de macronutrientes pela cana de açúcar irrigada no Semiárido brasileiro.

A marcha de absorcao de nutrientes, estabelecida por uma curva de acumulo de nutrientes na planta ao longo de seu ciclo, indica a fase de desenvolvimento da cultura que apresenta maior exigencia de um determinado nutriente. Objetivou-se determinar o acumulo e exportacao de macronutrientes pela cana-de-acucar, variedade RB92579, cultivada remcondicoes tropicais semiaridas na Usina Agrovale, em Juazeiro-BA, regiao do Submedio do Vale do Sao Francisco. O experimento foi conduzido em um Vertissolo Hidromorfico. Foram demarcadas 03 subareas nas quais se coletou amostras de material vegetal separadas em folhas verdes, bainhas, folhas e bainhas mortas, pseudocolmo, colmo e a parte imatura, em dez epocas ao longo do ciclo (66, 87, 112, 133, 168, 220, 242, 280, 352 e 385 dias apos o corte - DAC). As amostras foram levadas a estufa a 65 o C ate peso constante para obtencao da biomassa seca, na qual foram determinados os teores de N, P, K, Ca, Mg e S. A maxima absorcao dos nutrientes pela cultura da cana-de-acucar ocorreu no periodo compreendido entre 220 a 352 DAC. O acumulo de nutrientes obedeceu a seguinte ordem decrescente: K > N > Ca > S > P > Mg. A colheita e responsavel pela maior exportacao de nutrientes acumulados pela cultura da cana-de-acucar, cerca de 60 a 90 % do total de nutrientes acumulados sao exportados pela colheita. Durante o ciclo de cana-soca, foram utilizados pela variedade 2,50; 0,33; 5,35; 0,86; 0,19; 0,55 kg de N, P, K, Ca, Mg e S, respectivamente, para cada tonelada de colmo produzida.

Potencial de água no solo e na folha da videira "Sugraone" sob déficit hídrico

This study aimed to measure the variation of soil and leaf water potential in the Sugraone (Superior Seedless) grape, as well as the berry growth, under different irrigation conditions in the Fazenda Agrobras Tropical do Brazil S/A, in Casa Nova, BA, in October, 2007 during maturation stage. The Superior Seedless cultivar was irrigated at 21, 13 e 5 days before harvest with water depths of 100, 50 e 0% of crop evapotranspiration (ETc) and an additional treatment consisting of the farmer management. The results of leaf water potential using a pressure chamber and the respective soil matric potential from tensiometric readings are shown. Measurements of leaf water potential reached values from -0,95 to -1,80 MPa, at noon and from -0,10 to -0,27 MPa, at pre-dawn. Soil water matric potential varied from -5 to -79,5 kPa, for the least water deficient treatments. Results from leaf water potential show that in some days the plants were under moderate stress and in others under severe stress, independently of water deficit treatments. Although pre-dawn leaf water potential indicated that the vines were under mild stress or under adequate water management practices, even under low soil matric potentials, there was no significant reduction in berry growth.