Propagação tridimensional da frente úmida por cápsulas porosas.

Abstract

This work consisted in the three - dimensional study of the propagation of the wet front, under non - permanent conditions, through the use of porous capsules as irrigation method. This study makes it possible to define the spacing between the porous capsules and between the plants, besides providing the amount of water released to the plants. The tests were conducted in the Hydraulic Laboratory of the Department of Civil Engineering of the CCT / UFPb, using the porous capsule, and the material used for the propagation of the wet front was fine sand and a soil whose characteristics were described in the text. An electronic data acquisition system was used efficiently in data collection under transient conditions and the experiments were conducted in a reduced model of cylindrical PVC. The physical characteristics, such as suction, hydraulic conductivity and diffusibility as a unique function of the moisture content of the matrices used, such as fine sand and soil, were determined in the laboratory with equipment specially developed for this purpose. The 3-dimensional study provided a better understanding of the phenomena involving the complex processes of wetland spread, which was useful for the development of a practical method of irrigation, economically using the water resources of semi-arid regions that are rapidly declining , due to high rates of evapotranspiration and poor utilization of available resources. Measurement of the amounts of water released under different pressures, wet matrix volumes, maximum radial spreads and corresponding infiltrations and their respective rates of advance, and wet bulb area as a function of time and interpretation of these resulted in the characterization of bulb formation , for subsequent use in determining the number of pits and spacing of plants, under given application of pressure to the desired soil type. Uniformity tests, regression analysis and correlation were done to prove the validity of the results obtained in laboratory experiments. The work then presents a relevant importance for the needs of northeastern Brazil in general and of Paraíba in particular, presenting excellent use of water in the semi-arid hinterland, especially in the exploitation of vegetables and other subsistence crops of small and medium producers.