Water Table Level Effects on Cranberry Irrigation Management.

Improving irrigation practices in cranberry is motivated by interest in sustainability criteria and increasing regulatory pressure to monitor water use. Sub-irrigation from a water table allows growers to use low-power pumps at off-peak rates, to reduce irrigation costs in cranberry production. Earlier research on precision irrigation in cranberry demonstrated that initiating irrigation at soil water potential of -7.5 kPa caused no yield loss, but -10 kPa did. In the present study, -7.5 kPa was used as an irrigation threshold and water table depths between 40 and 90cm were established. We measured water potential at 6 and 21cm and the water content between those depths. The amplitude of water potential change in the root zone between irrigations was a function of water table depth. The water content was also a function of water table depth but was stable for all depths, rarely changing more than 0.02 from day to day. We hypothesize that upward flow from the water table is able to resupply the root zone with a majority of evapotranspiration losses for all water table depth treatments. In deeper water table plots the potential gradient increased to induce flow, while in shallower plots the high K(theta) allowed adequate flow with only tiny gradients. Numerical simulations with the Hydrus model and measured K(theta) determined in core samples confirmed that this was the case. The self-regulating of capillary rise in cranberry beds allows growers to determine optimum water table levels by monitoring root zone water potential fluctuations.

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See more from this Division: SSSA Division: Soil & Water Management & Conservation
See more from this Session: Soil & Water Management & Conservation: II

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