Spatial-temporal analysis of soil water storage and deep drainage under irrigated potatoes in the Central Sands of Wisconsin, USA

Knowledge of soil water storage and deep drainage is important for improving irrigation efficiency, maximizing crop water use, and understanding groundwater table fluctuation. This is particularly important in sandy soils that depend on irrigation to produce high crop yields. In sandy soils under potato in the Wisconsin Central Sand Plains, soil water storage using tension probes was measured in three irrigation zones over the 2014 and 2015 growing seasons. Soil water storage was estimated across a 78 ha field using apparent electrical conductivity maps. Deep drainage was estimated using the Richards’ equation and Hydrus-1D software. It was found that the average soil water storage ranged from 74 to 110 mm in the top 0.45 m in three irrigation zones in 2014, and from 70 to 95 mm in 2015. Rainfall and irrigation was 387 and 269 mm in 2014, and 328 and 281 mm in 2015. Estimated deep drainage was uniform in three irrigation zones, and ranged from 222 to 244 mm in 2014, and from 167 to 180 mm in 2015. A negative correlation was found between soil water storage and potato yields possibly due to over-irrigation. The methods used in this study can be applied to improve irrigation and water use efficiency.