Soil Water Dynamics of Shallow Water Table Soils Cultivated With Potato Crop

Abstract

Core Ideas Estimation of water table level supplies upward water flux for daily ETc needs. Episodic master recession method informs water table control during rain events. Water table recession varies by soil and irrigation, with fastest rates under subirrigation. Irrigation depth may be reduced in sprinkler areas with water table management. Agricultural areas with shallow water tables usually rely on upward soil water flux to supply crop evapotranspiration (ETc). The study objective was to determine optimum water table levels for coarse‐textured soils cultivated with potato (Solanum tuberosum L.) by estimating the upward soil water flux under different irrigation methods. Potato was grown under seepage, subirrigation with tile drainage, subsurface drip irrigation (SDI), and sprinkler irrigation. Irrigation zones were classified as sandy soil with low soil organic matter (SOM) and high bulk density (Bd), or loamy sand soil with high SOM and low Bd. Upward soil water flux supplied enough water to the root zone to meet ETc when the water table was at the 69‐cm depth for loamy sand soils under seepage, and 42 and 45 cm for sandy soils under subirrigation and SDI, respectively. The sprinkler‐irrigated area had no control over the water table, whereby the cumulative contribution of upward water flux still averaged 6.3 cm, suggesting that irrigation rates could be reduced if the water table is controlled and upward flux accounted for in the crop water balance. Rainfall introduces flooding risks and crop losses, but these risks are minimized with management. The water table elevation/precipitation ratio was 34.4 and 25.6 cm cm−1 of rain for loamy sand and sandy soils. After precipitation, the water table returned to the original levels twice as fast under subirrigation than with other methods given improved drainage capacity. Soil characteristics, irrigation method, upward water flux, and proper water table management are important factors for maintaining ideal soil moisture conditions in the crop root zone, minimizing flooding risk.