Effects of seawater irrigation on fruit quality of grapevine, soil properties and microbial diversity

Extensive researches have been conducted over the decades to investigate the effects of seawater on many crop plants, either by irrigation or foliar spray, in an attempt to enhance yield and quality, but there are few studies on the effects of seawater irrigation on soil properties. The purpose of this study was to determine the effects of seawater irrigation on the fruit quality of Cabernet Sauvignon grapevines, soil pH, soil salinization, soil bulk density properties and soil microbial diversity. Field experiments were conducted using seawater (10% concentrations) during the fruit expansion period, the early veraison period, the veraison period and the late veraison period in Penglai (pH 6.5–6.7). Seawater irrigation led to increased levels of fruit soluble solids, phenolic content, anthocyaninand sugar/acid ratio, resulting in slowly-increased pH values of soils. After 4 years of continuous seawater irrigation, the pH value of the 0–20 cm soil layer increased 0.24 units at the vineyard of the Guobin Winery and increased 0.17 and 0.18 units after one and two years of seawater irrigation, respectively, at the vineyard of the COFCO Winery. Moreover, seawater irrigation did not affect soil properties, since soil bulk density, specific gravity and porosity did not differ significantly from the control soil. Furthermore, seawater irrigation had less effect on the types of soil microbial communities. The results suggest that combined with rainfall, seawater irrigation could be useful for improving fruit quality and soil pH without inducing secondary soil salinization problems, and seawater irrigation could be used in acidic vineyard soils.