Evaluating the Effects of Mulch and Irrigation Amount on Soil Water Distribution and Root Zone Water Balance Using HYDRUS-2D

Abstract

Water scarcity is the most critical constraint for sustainable cotton production in Xinjiang Province, northwest China. Drip irrigation under mulch is a major water-saving irrigation method that has been widely practiced for cotton production in Xinjiang. The performance of such an irrigation system should be evaluated for proper design and management. Therefore, a field experiment and a simulation study were conducted to (1) determine a modeling approach that can be applied to manage drip irrigation under mulch for cotton production in this region; and (2) examine the effects of irrigation amount and mulch on soil water distribution and root zone water balance components. In the experiment, four irrigation treatments were used: T1, 166. 2623T1 to T4, while a lot of stored soil water in the root zone was utilized and a huge amount of water was recharged from the layer below 70 cm to compensate for the decrease in irrigation amount. Mulch significantly reduced evaporation by 11.7 mm and increased root water uptake by 11.2 mm. Our simulation study suggests that this model can be applied to provide assistance in designing drip irrigation systems and developing irrigation strategies.

Effects of Turfgrass Thatch on Water Infiltration, Surface Runoff, and Evaporation

“…For instance, the cumulative evaporation of soil moisture was lower in mulched soils than bare soils, and the reduction was related to mulch coverage and mass [16] [20].…”

Root Development of Transplanted Cotton and Simulation of Soil Water Movement under Different Irrigation Methods

“…The HYDRUS-2D model and the dual crop coefficient approach of FAO-56 were calibrated using the measured data in 2014, and produced a cumulative bias under the extreme rainfall conditions in 2013. Nevertheless, the simulated and measured results in 2013 still exhibited highly consistent trends, with several consecutive irrigation and precipitation events in the transplanted cotton growing seasons, particularly considering the complexity of the conditions to which the model was applied (i.e., heterogeneous soil properties, a more than 120-day simulation period, high evaporative demand, and assumed constant root distribution in one growth stage) [21,24].…”

“…Overall, the changes in the simulated SWCs at 0-30 cm were more drastic than those at 30-90 cm in both irrigation treatments (Figures 11 and 12), since the 0-30 cm layer is more directly affected by irrigation, precipitation, evaporation, and transpiration [21,24]. The simulation results in Figures 11 and 12 showed that the HYDRUS-2D model overestimated the SWCs in July 2013.…”

“…HYDRUS-2D is a hydrologic model that simulates water movements in two-and three-dimensional, variably-saturated porous media based on the numerical solution of the Richards equation [19,21,22,[24][25][26] and has been successfully used to model soil water movement under different irrigation methods, such as SDI, subsurface drip irrigation and flood irrigation [22,24,[27][28][29]. Previous simulation studies [19,21,22,24] have shown that the results for the soil water content (SWC) simulated by HYDRUS-2D are in reasonable agreement with measured values. Soil water movement associated with root water uptake is complex, and has been studied using empirical, analytical, and numerical models in the past decades.…”

“…The use of computer simulations with validated mathematical models is a rapid and inexpensive approach, which has received a great deal of attention during the past few decades [18][19][20][21][22][23][24][25]. HYDRUS-2D is a hydrologic model that simulates water movements in two-and three-dimensional, variably-saturated porous media based on the numerical solution of the Richards equation [19,21,22,[24][25][26] and has been successfully used to model soil water movement under different irrigation methods, such as SDI, subsurface drip irrigation and flood irrigation [22,24,[27][28][29]. Previous simulation studies [19,21,22,24] have shown that the results for the soil water content (SWC) simulated by HYDRUS-2D are in reasonable agreement with measured values.…”