ISHS Acta Horticulturae 664: IV International Symposium on Irrigation of Horticultural Crops
SOIL WATER DYNAMICS IN THE ROOT ZONE OF A MICRO-SPRINKLER IRRIGATED ALMOND TREE |
| Authors: | K.S. Koumanov, J.W. Hopmans, L.J. Schwankl |
| Keywords: | root water uptake, microsprinkling, water balance, fruit trees |
| Abstract:
The spatial and temporal pattern of root water uptake in partially wetted soil was studied in the root zone of a six-year old micro-sprinkler irrigated almond tree. The water balance of about one quarter of the root zone’s wetted soil volume (2.0 x 2.0 x 0.9 m) was determined by neutron probe and tensiometer measurements. Soil water content was measured at depths of 15, 30, 45, 60, 75, and 90 cm using PVC neutron probe access tubes, installed in a square grid of 50cm spacing to a depth of 120cm. Soil water potential gradients at the bottom of the monitored soil volume were estimated by eight pairs of tensiometers at depths of 82.5 and 97.5 cm, installed in a regular pattern between the access tubes. After linear interpolation of the tensiometer data across the experimental plot, vertical water fluxes at the 90 cm soil depth were evaluated for all access tubes locations. Neutron probe and tensiometer readings were taken at time intervals of 4 to 24 hours. The rate of soil water depletion was calculated and used to estimate the spatial and temporal distributions of root water uptake. Soil water dynamics was studied in two stages: 1) during a week of conventional irrigation management with three irrigation events; and 2) during a period of 16 days without irrigation, after the monitored soil volume was thoroughly moistened so that soil water was easily available everywhere, initially. The zones of maximum root water uptake were the same for both stages in periods of high local rates of water application. Hence, the almond tree appeared capable to redirect its root activity towards regions of the most favorable water regime with minimum soil water stress. After water applications, root water uptake developed initially near the tree trunk, progressing towards the periphery of the root system, shifting to root zone regions with minimum soil water stress, thereby changing locations of maximum root water uptake. | |
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