Analysis of infiltration and runoff in an olive orchard under no-till

Four infiltration techniques (falling head, ring, rainfall, and tension infiltrometer) were used to determine the saturated hydraulic conductivity, K-s, and the wetting potential front, h(f), of the Green-Ampt model. Water release curves from soil cores were also used for estimating h(f). The objective was to compare the performance of the different techniques for the assessment of infiltration in a no-tillage olive (Olea europaea L, subsp, europaea) orchard. Measurements were performed in two areas of the orchard, below canopy (C) and interrow among trees (IR), With the exception of the tension infiltrometer, all techniques showed significant differences in K-s and h(f) between C and IR areas, attributed to different compaction. Differences in K-s among techniques were within the range observed previously. The h(f) estimated from the falling-head technique was significantly higher than that measured with the other techniques. The discrepancies in the results obtained with the tension infiltrometer were attributed to insufficient time of measurement, leading to recommendations for a different field procedure and analysis of this technique. To assess the use of the techniques described above for the characterization of plot infiltration, rainfall and runoff were measured in a 128-m(2) plot. A numerical model was then used to predict runoff using the infiltration measurements. The results showed that runoff prediction is improved when different values of K-s and h(f) are considered for the C and IR areas instead of a single average value. The numerical analysis of the effects of tree arrangement on runoff prediction from infiltration measurements indicated that if the trees were placed along the contour lines, runoff would decrease relative to the standard tree arrangement.