Soil moisture distribution under drip irrigation and seepage for potato production

• Drip irrigation resulted in irrigation water saving compared to seepage irrigation.
• Comparable potato yields were achieved with surface drip irrigation and seepage.
• Subsurface drip irrigation resulted in limited soil water capillarity and reduced yields.

Keeping soil moisture content at field-capacity in the root zone tends to maximize crop yield. However, this is challenging in sandy soils with a shallow water table and low water holding capacity. Seepage irrigation (SEP) relies on capillarity water movement from a water table to irrigate the crop, creating uneven soil moisture distribution across the field, which could be improved with drip irrigation. The objectives of this study were to evaluate irrigation water use efficiency (IWUE) for potatoes and soil moisture distribution uniformity of two drip tape installation depths (surface at 0.05 m, SUR and subsurface at 0.15 m, SUB) as an alternative method to SEP. The design of the experiment was a randomized complete block with irrigation treatments as main plots, and potato varieties (Atlantic, Fabula, and Red LaSoda) as subplots. The volume of water applied, water table level, and soil volumetric water content were continuously measured for two seasons, 2011 and 2012. Drip irrigation significantly increased the moisture distribution uniformity in the potato ridge. The majority of the plant root system was concentrated in the upper soil layer (∼0.3 m), regardless of irrigation treatment. Similar marketable yield between SUR and SEP were achieved for Fabula and Atlantic in the first season, while lower yields were reported for Red LaSoda under drip in both years. The SUB produced lower yield in both years attributed to limited water capillarity. Drip irrigation reduced water use 48% and 88% in 2011 and 2012, respectively. Higher IWUE was obtained with drip compared to SEP for all varieties in 2012. The SEP used more irrigation water to supply the crop than SUR resulting in a difference in IWUE of 5.7 kg m−3. The SUR was capable of adequately irrigating the potato shallow root producing similar yield to SEP for Atlantic and Fabula varieties.