Effect of foliar seawater application on berry quality and ion distribution of ‘Kyoho’ grapevine yards

Abstract Extensive research has been conducted over the years to investigate the diverse effects of seawater on many crop plants either by irrigation or foliar spray in an attempt to enhance the yield and quality. The purpose of this study was to quantitatively determine the effects of foliar seawater application on berry quality and ion distribution of ‘Kyoho’ grape vineyards. A field experiment was conducted using diluted seawater starting at veraison followed by seven-day intervals between the treatments. While leaf contained K+ as much as Ca2+, which was at least eight times higher than Mg2+ and Na+, berry displayed different profiles as shown by significant decreases in K+ (22.4%) and Mg2+ (30.8%) with almost no changes in Ca2+ and Na+. Concentrations of cations were much higher than those of anions in control vineyard soil under this study. Foliar seawater treatment did not change the amounts of K+, Na+, HCO3−, and NO3− but significantly increased the amounts of Ca2+, Mg2+, and Cl− in vineyard soil. Declined ratios of K+/Na+ and Mg2+/Na+ were observed in both leaf and berry after foliar seawater application, but percentages in the declined ratios were significantly higher in leaf. In contrast to berry and leaf, vineyard soil had significantly increased ratios of Mg2+/Na+ and Ca2+/Na+ along with an unchanged ratio of K+/Na+ after foliar seawater application. Substantially decreased activities of antioxidant defensive enzymes (CAT, POD and APX) were observed in the post-seawater treatment leaves. Foliar seawater application resulted in high accumulation of proline, soluble proteins, and malondialdehyde (MDA), as well as an improved soluble solid content (SSC), redness, and color index for red grapes (CIRG) in berries without losing weight, firmness and yield. Leaf SPAD (chlorophyll value of leaf), soluble sugar and starch in branch were not affected despite the elevated level of Cl- in soil by foliar seawater treatment. Taken all the results together, foliar seawater treatment starting at veraison could be useful for improving ‘Kyoho’ grape berry quality without affecting the vegetative growth under the soil conditions used in this study.