Abstract
The low permeability of soil and high investment of salt management pose great challenges for implementation of land reclamation in coastal areas. In this study, a temporary soil leaching system was tested in which bundled maize straw (straw drainage module, SDM) was operated as a subsurface drainage tube and diluted seawater was used for leaching. A preliminary field experiment was conducted in coastal soil-filled lysimeters to examine the system’s feasibility and a numerical model (HYDRUS-3D) based on field measured data was designed to simulate the entire leaching process. The simulation results showed that the soil water velocity and the non-uniformity of salt distribution were apparently enhanced in the region approaching the drain outlet. The mass balance information indicated that the amount of water drained with SDM accounts for 37.9–66.0% of the total amount of leaching water, and the mass of salt removal was about 1.7 times that of the salt input from the diluted seawater. Additional simulations were conducted to explore the impacts of the design parameters, including leaching amount, the salinity of leaching water, and the number of leaching events on the desalination performance of the leaching system. Such simulations showed that the salt removal efficiency and soil desalination rate both were negatively related to the seawater mixture rate but were positively associated with the amount of leaching water. Increasing the leaching times, the salt removal efficiency was gradually decreased in all treatments, but the soil desalination rate was decreased only in the treatments leached with less diluted seawater. Our results confirmed the feasibility of the SDM leaching system in soil desalination and lay a good foundation for this system application in initial reclamation of saline coastal land.
Highlights
Farmland shortage is becoming increasingly severe in Eastern China due to fast population growth and urbanization progress
We propose a hypothesis that the straw drainage modules (SDMs) is regarded as a hydraulically-equivalent soil, and the initial values for straw hydraulics parameter estimation refer to Hudan and Sultan’s [35] experimental study, in which their data was obtained from a hydraulic-parameter inverse estimation of the straw interlayer
The calibration of water content shows a good agreement in both positions (Figure 2), The calibration of water content shows a good agreement in both 2positions (Figure 2), and the statistical and the statistical errors parameters (RMSE, ME, NSE, and R ) values in Table 1 ranged within errorsacceptable parameters (RMSE, ME, NSE, and R2 ) values in Table 1 ranged within acceptable limits compared limits compared with similar studies [18,24]
Summary
Farmland shortage is becoming increasingly severe in Eastern China due to fast population growth and urbanization progress. Exploitation and development of the coastal mudflat areas are regarded as an essential approach to relieve the stress of inadequate land resources [1]. Due to saline shallow groundwater and periodical seawater inundation, salt-affected soil with over-dispersed particles, aeration issues, and low water permeability is widely distributed in coastal areas, which increases the difficulty for the remediation of soil property. Water and nutrient absorption of root systems could be destroyed when crops are grown on soil contaminated with a high concentration of soluble salt. Soil salinization is a massive encumbrance to both the efficiency of land reclamation and the development of coastal agriculture [2].
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