Temporal changes in soil hydraulic conductivity with different soil types and irrigation methods

The soil hydraulic conductivity (K) is an important parameter for understanding soil hydrologic processes. K varies with time, soil type, and irrigation method. Understanding and predicting the temporal variability of K are required for irrigation design and numerical analyses. The objective of this study was to investigate and evaluate the temporal variability in K from April to September of 2008 in two soils, clay loam (CLS) and sandy loam (SLS), and two irrigation methods, furrow irrigation (FIM) and drip irrigation (DIM). Five sets of infiltration measurements with five replications were taken in grape fields using a tension infiltrometer at supply h values of -15, -6, -3, and 0 cm. The results showed that K had significant temporal differences under all supply h values. Generally, K initially exhibited high values and decreased from April to September. K of SLS was always significantly higher than that of CLS. K values were lower and varied more for FIM than for DIM, but showed no statistically significant difference between the two irrigation methods. About 1.3 to 2.9 times differences existed between the maximum mean K (in April) and minimum mean K values (in July/September) through the whole growing period. However, the relative errors between the calculated K and measured K diminished within 10% when K was estimated using a regression to adjust K to the number of irrigation events. These results contribute to a more accurate description of K for irrigation design and water flow modeling. (C) 2012 Elsevier B.V. All rights reserved.