EFFECT ON SOIL PROPERTIES AND MAIZE GROWTH BY ALTERNATE IRRIGATION WITH BRACKISH WATER

摘要

With growing competition for freshwater by industrialization and urbanization, brackish water irrigation has been increasingly used for agricultural production. One of major concerns is the accumulation of salt and its impacts on soil properties and crop yield. If properly managed, alternate irrigation with brackish and freshwater might alleviate the adverse impacts of salt on soil physicochemical properties and plant growth. To exploit proper alternate irrigation to minimize such impacts, a maize pot experiment was conducted at three stages (seedling, jointing and tasseling, and after tasseling) with three alternate irrigation methods (BFF: brackish-fresh-fresh, FBF: fresh-brackish-fresh, and FFB: fresh-fresh-brackish) and with three salinities (1.69, 4.81, and 7.94 dS m(-1)), respectively. The results show that compared to freshwater irrigation, alternate irrigation with high-salinity brackish water increased soil electrical conductivity by 4.1% to 207.4% and reduced soil infiltration rate by 19.2% to 51.9%. The adverse impacts were more prominent in FBF and FFB than in BFF due to the higher proportions of brackish water in FBF and FFB. High-salinity brackish water also caused salt stress on maize growth and decreased evapotranspiration, relative water content, intrinsic water use efficiency, and electron transport rate by 6.6% to 30.6%, 2.1% to 10.2%, 7.3% to 17.9%, and 7.2% to 39.6%, respectively, leading to reduced growth and productivity. The salt stress was more pronounced in BFF and FBF than in FFB because maize is more salt-sensitive during the vegetative stage. Overall, brackish water irrigation at the jointing and tasseling stage (FBF) caused the most severe impacts on both soil and maize, so freshwater is advocated at this stage. In BFF, due to sufficient freshwater irrigation at later stages, slightly saline irrigation can be applied at the seedling stage without evident adverse effects. Higher-salinity brackish water was used successfully in the after-tasseling stage (FFB), although salt leaching by off-season rainfall was needed after harvest for sustainable production.