Necessidades hídricas de citros e macieiras a partir da área foliar e da energia solar

Abstract

RESUMO -A energia solar é a fonte primária para a fotossíntese e a transpiração vegetal para que uma cultura expresse seu potencial produtivo em um dado local. o método proposto neste estudo pretende facilitar o cálculo do volume de água (litros/planta/dia) necessário para uma irrigação localizada com o mínimo desperdício possível em pomares cítricos e de macieiras, utilizando-se de dados usualmente disponíveis, tais como área foliar, densidade de fluxo de radiação solar global, saldo de radiação e déficit de saturação de vapor médio diário do ar. Considerando-se que a irrigação localizada consome bem menos água do que o sistema de aspersão, e que a outorga de água para irrigação está cada vez mais limitada, tal estudo vem a ser certamente de grande importância para assegurar a autossustentabilidade da agricultura irrigada, especialmente em regiões áridas e semiáridas. Foram utilizados neste trabalho, para desenvolvimento da metodologia proposta, dados de fluxo de seiva medidos através do método de fluxo de calor, em pomar de lima-ácida-Tahiti com área foliar de 48 e 99 m 2 , bem como em pomar de macieiras com área foliar aproximada de 5; 8; 9; 11; 16 e 21 m 2 . os resultados obtidos indicaram que a metodologia proposta, baseada na habilidade das plantas em converter energia solar fixada em água transpirada, mostrou-se viável para avaliar a lâmina de irrigação de plantas cítricas e macieiras nas localidades estudadas. Termos para indexação: irradiância solar, saldo de radiação, modelagem, consumo de água, espécies frutíferas. WATER REQUIREMENTS OF CITRUS AND APPLE TREES AFFECTED BY LEAF AREA AND SOLAR ENERGYABSTRACT -Solar energy is the primary source for photosynthesis and transpiration in such a way as to assure the expression of the crop yield potential at a given site. The current methodology aims to ease the calculation of the water amount (liters/plant/day) necessary for a localized irrigation scheduling with a minimal loss possible at both citrus and apple trees orchards by means of usual available data, such as leaf area, global solar radiation flux density, net radiation and air daily mean steam saturation deficit. Taking into account that the localized irrigation system takes up far less water than sprinkler systems and also that the grant of water for irrigation is becoming more and more limited, such a work certainly comes to be of a great importance to assure the sustainability of the irrigated agriculture, especially at both arid and semi-arid regions. For the development of the proposed methodology a data set of sap flux measured by means of the heat flux approach in a citrus orchard, cultivar Tahiti, with leaf areas of 48 and 99 m 2 , as well as in apple trees with leaf areas roughly of 5, 8, 9, 11, 16 and 21 m 2 was used herein. The obtained results revealed that it is rather feasible to estimate the amount of irrigation water throughout the whole citrus and apple trees cycle by means of the criterion based on the physiological variable input, which expresses the ability of the plants to convert...

Morpho-physiological characteristics of Jaffa orange trees (Citrus sinensis L.) in response to soil water deficit

“…Leaf transpiration rate decreased as a result of partial stomatal closure due to the stress caused by the water deficit. It may be implied that this type of response, given by stomata of citrus crops, occurs when there is water deficit, as an adaptation which aims at saving water, because there is high resistance and waxiness on the leaves (Pereira et al, 2009).…”

Atemoya sap flow estimation as a function of leaf area and reference evapotranspiration

“…Witght et al (1986) used a model that considered the leaf area index to calculate the potential transpiration of native semiarid pasture as a function of ETo and crop coefficient. According to Pereira et al (2009), the use of transpiration modeling presents simple calculation; however, its application is specific to each species and meteorological conditions under study.…”

Mathematical models to estimate leaf area of citrus genotypes

“…Leaf area is a variable of extreme importance to physiological and agronomic studies, such as vegetable growing, interception of light, remote sensing, photosynthetic efficiency, absorption of carbon, evapotranspiration, absorption of agrochemicals by the leaves, assessment of pest attack and irrigation management (Coelho Filho et al, 2004Guimarães et al, 2013;Griffith et al, 2011;Lopes and Pinto, 2005;Oliveira et al, 2013;Pereira et al, 2009;Silva et al, 2008;Stuckens et al, 2009). …”