Agricultural Water Management (Oct 2023)
Simulation of root zone soil water dynamics under cotton-silverleaf nightshade interactions in drip-irrigated cotton
Abstract
The uncontrolled establishment of weeds in upland cotton (Gossypium hirsutum L.), especially perennial silverleaf nightshade (Solanum elaeagnifolium), reduces lint yield and quality of cotton primarily by competing with cotton to limit essential resources such as water. Quantitative insight into the effects of cotton-silverleaf nightshade interactions on the root water uptake (RWU) in cotton is needed to develop weed management systems, particularly based on the critical periods of competitive water uses. A field experiment was conducted during two consecutive cotton growing seasons (2019–2020) to evaluate root zone soil water dynamics in subsurface drip-irrigated cotton under three treatments: only cotton plants (CP), only silverleaf nightshade plants (SNP), and cotton-silverleaf nightshade plants grown together (CP-SNP). The numerical model HYDRUS (2D/3D) was calibrated and validated using experimental data under the CP, SNP, and CP-SNP systems. The results of numerical simulations suggested that the HYDRUS (2D/3D) provided an effective tool for helping to understand and predict soil water dynamics and RWU under the CP-SNP competitive interactions at different cotton growth stages. Simulations showed that actual RWU (i.e., transpiration) and evapotranspiration rates remained higher under the CP-SNP treatment during two consecutive growing seasons, and RWU and evapotranspiration rates were in the order of CP-SNP > SNP > CP. The temporal variations in cumulative transpiration, evaporation, and drainage fluxes revealed that RWU solely contributed to higher evapotranspiration rates under the CP-SNP system as the magnitudes and patterns of evaporation and drainage fluxes remained similar among all the treatments. The temporal variations in RWU patterns at different cotton growth stages suggested that higher competitive RWU under the CP-SNP system than CP and SNP occurred during cotton’s leaf development and flowering growth stages, indicating critical periods for competitive soil water uses. Weed control measures during these critical periods are essential to minimize competitive water uses under the CP-SNP system in semiarid environments.
