What’s the effect of humic acid(HumiGrow) application on grape quality and yield of “flame seedless”?

The grape field was application during the two successive seasons 2017 and 2018 on 8 years old Flame Seedless grapevines to vertify the effect of berry thinning as cutting tip of 1/3 cluster singly or combined with nutrient of humic acid spraying on yield and fruit quality. The results showed that berry thinning insignificantly effect on yield/vine and cluster weight compared to untreated ones. However, berry thinning plus humic acid nutrients solution significantly increased the yield and cluster weight. All treatments significantly improved the berry quality in terms of increasing the berry weight,TSS/acid ratio and anthocyanin content and decreasing total acidity. The best recorded result was due to berry thinning plus humic acid application. Introduction Grape trees occupy more land in the world than any other single fruit and account for almost half of the total world production of all fruits. Grapes include more than 60 species and rank the top fruit crop all over the world and the second crop after citrus in Egypt. Fertilization and fruit thinning as a cultural practice, are of the important tools to increase the yield and improve the fruit quality. Flame seedless as a promising grapevine cultivar that grown successfully under Egypt environmental condition and has progressively developed in the last few years. Flame Seedless is one of the most popular cultivars of table grapes in Egypt. Cluster thinning is a technique often implemented in field conditions, as it is claimed to improve grape quality through an increase in total soluble solids.Cluster thinning resulted in increases of cluster weight, cluster size, berry size, berry color and index of maturity value. It decreased the yield and acidity values. Humic acid is the active constituents of organic humus, which can play very important role in soil conditioning and plant growth and they have different effects on plants(Ferrara and Brunetti,2010). Plant growth stimulating effect of humic substances is associated with increased macro-nutrient intake.Humic substances affect the ion exchange of plant nutrients that are useful in microbial activity by increasing conversions directly as well as result of the stimulating plant growth hormones.Humic acid plays an important role directly and indirectly in nutrition of the plants Lobartini et al. (1997). Humic acid application in the full bloom period increased significantly berry weight, titratable acidity and maturity index values of Italy grape cultivar (Ferrara and Brunetti, 2010 and Akin, 2011). Potassium (K) is a mobile element in the plant and is an activator of enzymes that are essential for photosynthesis and respiration as well as enzymes that produce starch and proteins. Humic acid products has been proved increasing the quality,shelf timne and yield of grapes especially to flame seedless.