Componentes do balanço de água em um Cambissolo cultivado com meloeiro irrigado por gotejamento, com e sem cobertura da superfície / Water balance components in an Inceptsol cropped with muskmelon drip irrigated, with and without covered surface

AUTOR(ES)
DATA DE PUBLICAÇÃO

2010

RESUMO

The knowledge about the soil water balance is essential to soil-water-plant system management. Thus, this research aimed to study the water balance components in an Inceptsol cropped with muskmelon under drip irrigation, with and without surface covering, in the county of Baraúna, Rio Grande do Norte State, Brazil (05º0448 S, 37º3700 W). In an experimental area of 20 m x 50 m grew up AF-646 muskmelon, spaced 2.00 m x 0.35 m, in a total of ten plants lines 50 m long each. At 1/3 and 2/3 of the length of each plant line, four tensiometers were installed, one in each depths of 0.1, 0.2, 0.3 and 0.4 m. The installation was made adjacent to the irrigation line (0.1 m from the plant line) between two selected plants 0.1 m apart. In five random lines, it was made a covering with dry leaves of banana (Musa sp.) along the drip line in the range of 0.5 m. In the other five there was no covering. Thus, the experiment consisted of two treatments whith ten repetitions in four phenological stages: initial (7-22 DAS - days after sowing), growing (22-40 DAS), fruiting (40-58 DAS) and maturing (58-70 DAS). Rainfall was measured with rain gauge and water storage estimated by trapezoidal method, from tensiometer readings and retention curves. To determine the soil water flux densities at the soil depth 0.3 m, tensiometers at depths 0.2, 0.3 and 0.4 m were considered; the tensiometer at 0.3 m was used to estimate the soil water content, from the soil water retention curve at this depth, and the other two to calculate the soil water total potential gradient. The flux densities were calculated by the Darcy-Buckingham equation, with the hydraulic conductivity being determined by the instantaneous profile method. There was no runoff and the crop actual evapotranspiration was calculated by the mass balance equation. It could be concluded that: a) at 0.2 m soil depth the hydraulic conductivity was low; b) controlled irrigation with tensiometers allowed a reduction of 45% in water application in relation to commonly used practice in the region, without crop productivity change; c) there was positive effect of soil covering on water storage, especially at the initial and vegetative stages; d) the method of soil water balance was efficient to estimate actual evapotranspiration, under irrigated muskmelon conditions; e) the application of a single irrigation depth daily, even in a short time period, presents risk of water to be lost by internal drainage, especially at initial and vegetative muskmelon stages; f) the spatial variability of soil water flux density was high when rainfall incidence occurred; g) there was no effect of covering on crop actual evapotranspiration, neither on yield and post-harvest fruits characteristics; h) the crop coefficient curve has severe limitations when used to provide water to the muskmelon.

ASSUNTO(S)

evapotranspiration soil water soil water balance inceptsol balanço hídrico cambissolos drip irrigation irrigação por gotejamento muskmelon. Água no solo melão. evapotranspiração

ACESSO AO ARTIGO

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