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Use of saline water for irrigation is essential to mitigate increasing agricultural water demands in arid and semi-arid regions. The objective of this study is to address the potential of using straw biochar as a soil amendment to promote wheat production under saline water irrigation. A field experiment was conducted in a clay loam soil from eastern China during 2016/2017 and 2017/2018 winter wheat season. There were five treatments: freshwater irrigation (0.3 dS m−1), saline water irrigation (10 dS m−1), saline water irrigation (10 dS m−1) combined with biochar of 10, 20, 30 t ha−1. Saline water irrigation alone caused soil salinization and decreased wheat growth and yield. The incorporation of biochar decreased soil bulk density by 5.5%–11.6% and increased permeability by 35.4%–49.5%, and improved soil nutrient status. Biochar also reduced soil sodium adsorption ratio by 25.7%–32.6% under saline water irrigation. Furthermore, biochar alleviated salt stress by maintaining higher leaf relative water content and lower Na+/K+ ratio, and further enhanced photosynthesis and relieved leaf senescence during reproductive stages, leading to better grain formation. Compared to saline water irrigation alone, biochar application of 10 and 20 t ha−1 significantly increased wheat grain yield by 8.6 and 8.4%, respectively. High dose of biochar might increase soil salinity and limit N availability. In the study, biochar amendment at 10 t ha−1 would be a proper practice at least over two years to facilitate saline water irrigation for wheat production. Long-term studies are recommended to advance the understanding of the sustainable use of straw biochar.

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Initial land reclamation of the saline soils often requires higher drainage intensity for quick leaching of salts from the soil profile; however, drainage pipes placed at closer spacing may result in higher cost. Seeking an inexpensive degradable organic subsurface drainage material may satisfy such needs of initial drainage, low investment and a heathy soil environment. Crop straws are porous organic materials that have certain strength and endurance. In this research, we explored the potential of using bundled maize stalks and rice straws as subsurface drainage material in place of plastic pipes. Through an experimental study in large lysimeters that were filled with saline coastal soil and planted with maize, we examined the drainage performance of the two organic materials by comparing with the conventional plastic drainage pipes; soil moisture distribution, soil salinity changed with depth, and the crop information were monitored in the lysimeters during the maize growing period. The results showed that maize stalk drainage and the rice straw drainage were significantly (p < 0.05) more efficient in removing salt and water from the crop root zone than the plastic drainage pipes; they excelled in drainage rate, leaching fraction, and lowering water table; and their efficient drainage processes lowered salt stress in the crop root zone and resulted in a slightly higher level of biomass. The experimental results suggest that crop straws may be used as a good organic substitute for the plastic drainage pipes in the initial stage land reclamation of the saline coastal soils.

The coastal regions of eastern China have substantial potential for agricultural production. Freshwater scarcity makes the utilization of plentiful brackish water a vital issue in this area. We aim to assess the effects of cycle irrigation with fresh and brackish water on soil salinity and maize (Zea mays L.). A pot experiment was performed with two typical coastal soils (sandy loam and silt loam) and one local maize cultivar. The maize growing season was divided into three phases (development, mid‐, and later stage). Cycle irrigation was conducted using brackish water (5 g NaCl L−1) during one stage and freshwater for the remaining stages. Cycle irrigation using brackish water at the development stage caused both osmotic and ionic stresses on the maize, leading to significantly‐reduced evapotranspiration (ET), increased stem and leaf Na+/K+ ratio, and stunted growth. The decline of kernel number and 100‐grain weight resulted in severe yield loss. Cycle irrigation with brackish water at the mid‐stage induced less adverse effects on crop growth, while the decrease in kernel number remarkably reduced the yield. Cycle irrigation with brackish water at the later stage minimized the impacts of saline irrigation on soil salinity and maize productivity. Nonetheless, salt leaching by off‐season rainfall and low salinity water and soil salt monitoring should be considered before the next season. Compared to sandy loam soil, silt loam displayed higher soil salinization, and lower maize growth and yield. Additional field research is recommended to facilitate the reliable use of coastal soil and water resources. Core Ideas Cycle irrigation with fresh and brackish water in two coastal soils is studied. Cycle irrigation using brackish water is effective when freshwater is scarce. Brackish water is proposed to be used at maize later reproductive stages. Sandy loam soil is preferable for cycle irrigation compare to silt loam soil.