XVII th World Congress of the International Commission of Agricultural and Biosystems Engineering (CIGR) WATER REDISTRIBUTION WITHIN THE POTATO ROOT ZONE FOLLOWING IRRIGATION CSBE100225 -Presented at ASABE's 9th International Drainage Symposium (IDS)

Abstract

ABSTRACT: Monitoring crop water uptake and soil water movement within the root zone is critical for designing drainage systems. The objective of this study was to monitor the water movement within the root zone after the soil was fully saturated by irrigation. This experiment was conducted in Winkler, Manitoba, in a potato field instrumented with 15 Time Domain Reflectometry (TDR) miniprobes embedded in a vertical plane within the root zone for each replicate. The TDR miniprobes were installed at five different depths (0.1, 0.2, 0.4, 0.6, and 0.8 m) and at three different radial distances (0.15, 0.3, 0.45 m) from the base of the potato plant. Three such replicates of TDR probes were installed at vertical planes located one meter apart. A 5 m by 5 m area was blocked off, and 50 mm depth of water was applied to bring the soil to saturation within this area. The initial water content measurement prior to this irrigation event and at periodic intervals thereafter was carried out over a four-day period. In general, the volumetric water content showed an increasing trend with depth during the four-day period. However, with time, the water content decreased in every layer except the deepest layer indicating upward movement of water from below the root zone. The results also showed that moisture depletion in the upper layers of soil was replenished overnight. The overnight increase in water content within the root zone can be attributed to capillary rise of water from below the root zone as well as hydraulic lift caused by the potato plants. Hydraulic lift is a phenomenon in which the plant roots act as a conduit, for water transport from deeper layers of soil to the drier shallower layers within the rootzone. This process is enhanced further in the absence of transpiration during the night. This paper presents evidence of this phenomenon in potato plants