Grapes, whether grown in open fields or backyard settings, are highly valuable fruit trees. In regions such as the giant peaks of Xi'an Yanqiao, the Hutai series in Huxian, and the Hongdi variety in northern Fujian, grape cultivation has become a major driver of local economic growth. However, for many years, growers have focused primarily on the use of nitrogen, phosphorus, and potassium fertilizers while neglecting the importance of trace elements like zinc. This has led to various physiological disorders, commonly referred to as physiological diseases.
Among these issues, zinc deficiency has become a growing concern among grape farmers. The increasing prevalence of this condition each year has caused significant losses in production. This article aims to provide an in-depth overview of the symptoms, causes, and effective correction methods for zinc deficiency, offering practical guidance for grape growers.
**First, the symptoms of zinc deficiency**
Zinc deficiency often begins with visible changes in the leaves. Leaves become smaller, narrower, and the internodes shorten, causing the leaves to grow densely and form rosette-like clusters. In some cases, the leaves may even curl into circular shapes. As the condition progresses, the leaves at the tip of the shoots may die off, leading to dry and weak growth.
From a fruit perspective, zinc-deficient vines experience poor pollination, resulting in seedless or misshapen fruits. These fruits are usually small, lack uniformity, and have little commercial value. The overall fruit set is reduced, and the size of the grapes becomes irregular, which can lead to a loss of the original variety’s characteristics.
On the tree level, zinc deficiency disrupts normal growth patterns, leading to reduced yields due to abnormal leaf, branch, and fruit development. The disordered structure also negatively impacts photosynthesis, further affecting the plant's health and productivity.
**Second, the main causes of zinc deficiency**
One of the primary reasons for zinc deficiency is improper fertilization practices. Many growers rely heavily on nitrogen, phosphorus, and potassium fertilizers without supplementing with essential micronutrients like zinc. Over time, this leads to a depletion of zinc in the soil, making it difficult for the vines to absorb sufficient amounts.
Additionally, excessive use of phosphorus-based fertilizers, such as diammonium phosphate or superphosphate, can interfere with zinc uptake. High levels of phosphorus create an antagonistic effect, preventing the plants from absorbing zinc properly. In calcareous soils, where calcium levels are high, zinc tends to precipitate and becomes unavailable to the roots.
**Third, corrective measures**
To address zinc deficiency, it is essential to replenish the missing nutrient. Spraying a 0.1% zinc sulfate solution 7 to 10 days before flowering can effectively prevent the onset of deficiency symptoms.
In areas with high lime content, it is important to avoid using calcium-rich fertilizers, as they can bind with zinc and reduce its availability. For such soils, applying chelated forms of zinc, such as Stadecopol, during the growing season can help improve absorption.
During the growing period, three applications of chelated trace elements, including zinc, can be sprayed onto the leaves or mixed directly into the fertilizer. This ensures that the vines receive the necessary nutrients in a readily available form.
**Fourth, agricultural practices to improve zinc uptake**
Alongside chemical treatments, proper agricultural management plays a key role in enhancing zinc absorption. Regular weeding, soil aeration, and the application of balanced organic-inorganic bio-fertilizers can significantly improve soil health and increase the efficiency of nutrient uptake. These practices not only support better zinc utilization but also contribute to the long-term sustainability of grape cultivation.
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