Water table contribution and diurnal water redistribution within the corn root zone

Understanding the water redistribution pattern within the corn root zone is crucial for water management. The objective of this research was to determine the water redistribution pattern within the corn root zone in response to irrigation and groundwater contribution. Water redistribution was monitored within the root zone of a cornfield located in Winkler, Manitoba, in 2009 and 2010 using time-domain reflectometry (TDR). Three replicates of fifteen TDR miniprobes were installed at 0.1, 0.2, 0.4, 0.6, and 0.8 m depths from the ground surface and at 0.12, 0.24, and 0.36 m radial distances from the base of the corn plant. The experimental site was irrigated by applying 50 and 65 mm of water on the soil surface in 2009 and 2010, respectively. The volumetric water contents at the 45 locations were measured prior to and at periodic intervals after the irrigation. The results indicated a pattern of water redistribution within the root zone, where the soil became drier during periods of high ET demand and became wetter during periods of low ET in the evening and night. Poorly drained soils may show a delay in the drying/replenishment pattern in dry years due to low hydraulic conductivity and deeper water table. The results from 2010 indicated that 81% of the crop water requirement was met from groundwater contribution during the experiment. During the extended period of steep water table drop, this contribution was 52%. Simulations of soil water content and upward flux using Hydrus-1D closely matched the observed values during the experimental period.