Effects of Saline Water Irrigation with Different Concentrations on Soil Water and Salt Distribution and Growth of Winter Wheat

Abstract

[Objective] Saline water irrigation is one of the important ways to alleviate the shortage of agricultural water and ensure food production. However, soluble salt in irrigation water leads to soil salt accumulation, which affects the growth of crops. Seeking a suitable salt concentration in irrigation water is a favorable guarantee for the safe utilization of saline water resources. [Methods] In this study, a rain-shielding pot experiment was conducted to plant winter wheat. The deionized water was used as a control (CK), and chloride salts were added to form saline water with different salt concentrations. The electrical conductivity of irrigation water (ECw) was 0.26 (CK), 3.00 (S1), 5.26 (S2), 7.07 (S3), and 9.24 (S4) dS/m respectively. The soil water and salt distribution, growth, photosynthetic physiology, and yield formation of winter wheat were studied. [Results] Soil water content and electrical conductivity increased with the increase of saline water salt concentration under saline water irrigation. When the conductivity of irrigation water was 9.24 dS/m, the soil moisture content was 5.43% (0—10 cm), 4.21% (10—20 cm), and 4.98% (20—40 cm) higher than CK, respectively. The electrical conductivity of soil extract (ECe) in 0-40 cm soil layer was 0.66, 4.89, 7.88, 9.34, and 10.16 dS/m under CK and S1-S4 treatments after winter wheat harvest, respectively. Compared with CK, there was no significant difference in the growth, photosynthetic physiological indexes, and yield of winter wheat when the conductivity of irrigation water was 3.00 and 5.26 dS/m, but it was significantly reduced when the conductivity of irrigation water was 7.07 and 9.24 dS/m. The net photosynthetic rate, maximum plant height, maximum leaf area, shoot dry matter mass at maturity stage, root dry matter mass and yield of winter wheat under 9.24 dS/m were decreased by 71.00%, 2.81%, 15.33%, 15.55%, 47.25%, and 27.53% compared with CK, respectively. The threshold of saline water conductivity for irrigation of winter wheat was calculated as 5.82 dS/m using the fitting sum of FAO piecewise function, if the value exceeded, the relative yield of winter wheat decreased by 8.80% with each increase of 1 dS/m. [Conclusion] In summary, the higher the salt concentration of irrigation water, the greater the impact on soil water and salt distribution and winter wheat growth, 5.82 dS/m is the threshold of saline water conductivity of winter wheat irrigation. Considering the growth, photosynthetic physiological indexes of winter wheat and soil physical and chemical properties, it is suggested that ECw should not exceed 5.82 dS/m when saline water is used to irrigate winter wheat. This study can provide theoretical support for the safe utilization of saline water.

Keywords

• saline water
• winter wheat
• salt tolerance threshold
• yield