This research had the objective of verifying the spatial and temporal variabilities in the advance phase and in the infiltration opportunity time, and their reflexes on the water application time in a furrow irrigation system with cutback flow for a sandy-loam soil. The field evaluations were conducted in the irrigation district of São Gonçalo, in the municipality of Sousa, Paraíba State, Brazil, where measurements were made in six equidistant furrows, in order to mostly comprise the variability all over the area, in the twelve irrigation events along the crop season. Observing the advance times and the infiltration opportunity times at the end of the irrigated area in each irrigation event and at each furrow irrigation along the time, it was verified that the spatial variation in the advance time was more expressive than the temporal variation, while in the infiltration opportunity time happened the inverse. Along of time and space, the minimum and maximum values of the advance time and of the infiltration opportunity time were, respectively, 15 and 62 min, and 1 and 517 min. These time amplitudes generated maximum spatial variations in the water application time, along the crop season, equal to 41.8%; spatially, the maximum temporal variations in the water application time was 71.6%. These values show how much the heterogeneity of the infiltration characteristics, as well as of the discharge, furrow wetted perimeter and required water depth, along of time and space, affects the optimization of the water application time.
advance time; water application time; furrow irrigation
