Medida da erosão na irrigação por sulcos com vistas à conservação de água e solo

Abstract

Erosion in furrow irrigated plots is a phenomenon of agricultural and environmental importance that, particularly in Brazil, has not received the attention that deserves. Experiments were conducted in two experimental units of an experimental farm in Pentecoste (Ceará - Brazil) aiming to quantify the amount of eroded soil provoked by furrow irrigation. The experimental units were chosen to represent typical soil textures in the irrigated perimeters areas of Northeastern Brazil: sandy loam (B -T2) and silty clay loam (C - S2). Each unit had 0.15 ha. The experiments were conducted from July to October 2010 and from July to October 2012. In each unit, nine furrows were monitored, corresponding to three inflow rate treatments with three replications for each inflow rate, leaving a non-monitored furrow between the test furrows and two furrows without irrigation delimiting the flow rates treatments. Flow rates were differentiated using different diameters of siphons (1 ", 1 ½" and 2 "). Irrigations were performed at intervals of no more than seven days. During the experiments, the following variables were analyzed: sediment concentration in the runoff water, variation of the furrow cross section geometry, the relation of soil loss and system performance measures (application efficiency and Christiansen´s uniformity coefficient) and the effects of erosion on soil fertility. The research revealed that the excess water from the furrow irrigation carried high sediment concentrations, ranging from 0.1 g L-1 to 7.0 g L-1,resulting in a soil loss of up to 20 Mg ha-1 yr-1. Soil loss increased with the inflow rate following a potential function. Other important factors - furrow length, slope and soil texture - must be also considered to improve management that minimizes erosion and optimizes the irrigation efficiency.