Abstract
Optimization of water use with consideration of salinity control is a crucial task for crop production. A new scheme, “optimized irrigation”, was recently presented to determine irrigation depth using WASH_1D/2D which are numerical simulation models of water flow and solute transport in soils and crop growth. In the scheme, irrigation depth is determined such that net income is maximized considering the price of water and weather forecasts. To evaluate whether the optimized irrigation is also able to restrict salinity stress and avoid salinization without any intentional leaching, we carried out a numerical experiment for winter wheat grown in northern Sudan under the following scenarios: (1) Available water in the root zone is refilled using freshwater (0.17 g/L of NaCl) at every five days; (2) available water in the root zone is refilled using saline water (1.7 g/L) at every five days; (3) optimized irrigation using fresh water at 7-days interval; (4) optimized irrigation on a weekly basis using saline water; and (5) same as scenario 2, except for leaching is carried out at the middle of the growing season and leaching depth is optimized such that net income is maximized. The results showed that the optimized irrigation scheme automatically instructs additional water required for leaching at each irrigation event and maximizes the net income even under saline conditions.
Highlights
Irrigation-induced salinity is a major threat for the sustainability of agriculture in arid and semi-arid regions
We will present a new scheme to determine leaching depth such that simulated net income is maximized under given water price. Another purpose of this study is to evaluate the new scheme to determine leaching depth in which leaching is performed only once during a cropping season can attain higher net income than the optimized irrigation scheme
We assume that a farmer can obtain virtual net income, In ($ ha−1 ), at each irrigation a farmer can receive income after harvest in reality
Summary
Irrigation-induced salinity is a major threat for the sustainability of agriculture in arid and semi-arid regions. Phogat et al [6] reported that, according to future climate projections, irrigation schedules without a significant leaching fraction might lead to a high salt build-up in the soil. To control salinity in the root zone for better crop growth, more water than that required to meet crop evapotranspiration must be applied to leach excessive soluble salts out [7]. Such an intentional “over-irrigation” is called leaching, which is the primary measure and widely practiced as the most effective method for removing salts from the rootzone.
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