Simulation of soil water flow and heat transport in drip irrigated potato field with raised beds and full plastic-film mulch in a semiarid area

Surface drip irrigation with full plastic-film mulch can increase crop yield and save water by regulating soil water and heat conditions for potato (Solanum tuberosum L.) production with raised beds in semiarid area where the rainfall is scarce and evaporation is high. For efficient use of plastic film mulch an understanding of the soil water flow and heat transport is needed. Here we use a model (HYRUS-2D) which is calibrated with field experiments to simulate soil water movement and heat transport. The field experiments were conducted with three treatments, characterized as wetted soil percentages: 35% (P1), 55% (P2), and 75% (P3). Furthermore, the effects of the uncertainty of key soil hydraulic parameters on soil water contents were evaluated using three approaches: (1) soil hydraulic parameters estimated from measured soil textural information (S1); (2) from experimentally measured soil water retention curve (S2); and (3) from inverse modeling (S3). The performance of S2 was the worst in all treatments; the root mean square error (RMSE) was > 0.05 cm(3) cm(-3). The performance of S3 was the best with RMSE ranged from 0.015 to 0.038 cm(3) cm(-3) at 10-50 cm soil depth. The simulated soil water in the raised bed decreased quickly after irrigation, maintaining adequate aeration for potato growth, irrespective of the wetted soil percentage. The downward transport of soil water still existed during the second and third days after irrigation in the simulations of the P2 and P3 treatments. The soil temperatures between the P1 and P3 treatments were similar. In conclusion, the HYDRUS-2D simulations could be used to estimate the soil hydraulic and thermal parameters with inverse modeling. The calibrated model can be used in the design and management of surface drip irrigation with raised beds and full plastic-film mulch to provide favorable soil water and heat conditions for potato growth.