Distribuição da água em solos irrigados por gotejamento.

Abstract

The main objective of the present work was to study the distribution of water in drip irrigated soils. The works were developed in two alluvial soils (light and medium texture) of the Arco Arco Irrigated Perimeter verde, located in the State of Paraíba and administered by the National Department of Works Against Drought (DNOCS). The results obtained, when these two soils were drip irrigated, with a flow rate of 4 liters per hour, allowed to conclude the following: The distribution of water content in the alluvial soil light texture, when drip irrigated, resembled if the distribution, in the sand soils irrigated by furrows, the presented by DAKER (1970). This water distribution characteristic was not observed in the medium texture alluvial soil. The maximum depths achieved by the effective bulbs were 90 to 70 cm for alluvial soils with light texture and alluvial medium texture, respectively. Both maximum bulbs were obtained after 100 hours of irrigation. For both soils during the first 20 hours of irrigation, when the soil was relatively dry, lateral infiltration was approximately equal to vertical infiltration. After 20 hours of dripper operation the vertical infiltration was greater than lateral infiltration. Most of the longitudinal areas of the effective bulbs, for both soils, were obtained during the first 60 hours of irrigation. Thus, with 42.8% of the total irrigation time, 65 and 61% of the areas were formed longitudinal dimensions of effective bulbs for light textured and medium textured soils, respectively. It was found that in the alluvial soil of light texture and it is possible to use greater spacing between drippers than in alluvial soil of texture average. Irrigation times and spacing between drippers were determined for crops with different depths of root zone, implanted in alluvial soils of light texture and media studied. The use of irrigation time or spacing between drippers, greater than those presented, will probably result in a decrease in irrigation efficiency.