Spatial variability of the hydraulic properties of a drip irrigated andisol under blueberries

Abstract

The objective of the present investigation was to identify the spatial variability of hydraulic properties of a volcanic ash soil under irrigated Blueberry crops, in order to improve the irrigation efficiency in a very sensitive crop by excess or lack of water. Undisturbed samples (230 cm 3 ) were collected in area of 945 m 2 (grid: 72 points separated by 3.2 and 6.4 m) between 1 and 7 cm depth in an Acrudoxic Fulvudands to determine the bulk density (Bd), total porosity (TP), the volume of water-filled pore space (ea (6kPa) ), plant available water (PAW), permanent wilting point (PWP) and saturated hydraulic conductivity (Ks). Along with sampling, volumetric water content (θ (Field) ) was measured using a TDR (grid: 120 points spaced by 1.4 and 3.2 m). From all results contour maps were developed, using geostatistical tools. The coefficient of variation of (θ (Field) ), Ks, (ea (6kPa) ) and PAW showed a moderate variability (15 % - 35 %). The dependence degree (DD) was considered as weak for θ (Field) , moderate for θ (6kPa) , ea (6kPa) , PAW and high for Bd, TP, Ks and θ (0.1kPa) . The properties with largest DD were soil structure-dependent, whereas, the lowest values were observed for those related to soil texture (in this case θ (Field) , which were close to the PMP). The spatial variability was related to the high water storage capacity and the ability of the soil to conduct water with different intensities, what is related to the amount of water-filled macropores.