Spring fertilization for grapevines should not be underestimated.

“A year’s plan begins in spring”—spring management before grape flowering is the cornerstone of the entire growing season. Poor practices can severely compromise yield and even weaken the vines. Among these tasks, fertilization prior to bloom is of paramount importance. Let’s take a closer look.

1. Early spring orchard sanitation work must be carried out effectively.

Nowadays, most grape growers have adopted the practice of applying a “post‑harvest” fertilizer in autumn, with base application as the primary method. They also carry out a more thorough orchard cleanup during winter, removing diseased fruits and branches and either burning them or burying them deeply, in order to minimize the risk of pests and diseases infecting the next growing season.

However, it cannot be ruled out that some fruit growers fail to thoroughly clean their orchards in autumn and winter. In such cases, if the winter is particularly cold and several heavy snowfalls occur during the “nine-nine” period of extreme cold, the insect eggs and other overwintering stages will suffer severe damage from the frigid air and ice, with most of them freezing to death. Consequently, the problem of inadequate pre‑spring orchard cleanup is relatively minor.

However, during the mild winter of 2018—when the rivers remained ice-free throughout the “three nines” and “four nines” periods, and snowfall was scarce—it became particularly troublesome to fail to thoroughly sanitize the orchard in spring, as this could easily lead to a surge in pests and diseases. Consequently, at the onset of spring in 2019, it was all the more critical to once again remove diseased fruits, infected branches, and old bark from the orchard and to apply either Bordeaux mixture or a dedicated orchard‑sanitizing fungicide.

Moreover, based on past experience, a late‑spring cold snap is more likely after a mild winter, so it’s important to take adequate frost‑protection measures for the grapevines.

2. Before grape buds break, prioritize nitrogen fertilizer to promote vigorous growth.

With spring returning to the land, all things awaken. When you notice grape bud scales beginning to swell, it’s time to apply a high‑nitrogen bud‑promoting fertilizer. Typically, this is applied in trenches using a high‑nitrogen compound fertilizer—such as a humic‑acid formula like 18‑15‑12 with an added microbial inoculant—combined with irrigation. The goal is to stimulate bud growth and encourage rapid extension and spreading. This is especially important when your orchard’s grapevines are weak; in such cases, this bud‑boosting fertilization becomes even more essential.

Of course, if your orchard received ample autumn “post‑harvest” fertilization, the vines are vigorous, and nutrient reserves are ample, you may skip this round of bud‑promoting fertilizer to avoid excessive shoot growth. Ultimately, whether or not to apply this fertilizer depends entirely on the grapevines’ current vigor.

3. Supplement zinc when you see sprouts.

Zinc is essential for growth; as we all know, zinc deficiency in children can lead to stunting, and the same holds true for plants. When plants are deficient in zinc, their growth slows, and they remain stunted. Therefore, supplementing with zinc during this critical period—when its demand is at its highest—is particularly important.

4. Supplement calcium through leaf application

Grape growers are well familiar with these practices. For novice growers who cannot yet apply fertilizer as skillfully as seasoned farmers—tailoring applications to the specific growth stages of the vines—it suffices to implement calcium supplementation once the grape leaves have fully unfolded.

Calcium fertilizer exhibits three peak accumulation periods during fruit tree growth: the first begins 20–30 days after flower fall, the second occurs during fruit enlargement, and the third takes place approximately 20–30 days before harvest.

So why don’t orchardists apply calcium fertilizer after flowering, instead opting for foliar calcium supplementation? This has to do with calcium’s unique properties—calcium is famously “lazy,” moving very slowly through the plant. That’s also why growers often combine calcium fertilization with boron application: boron is highly mobile and acts as an efficient transporter, swiftly delivering calcium to where it’s needed.

5. Apply boron and phosphorus before flowering to promote bloom development.

Boron promotes the development of reproductive organs. Foliar application of boron fertilizer one week before flowering, combined with a high-phosphorus fertilizer, can encourage blooming, resulting in healthier flowers and well‑developed floral structures. For weak trees, early‑spring foliar sprays of boron on bare branches can also be tried—both to guard against late spring frosts and to stimulate flower bud differentiation—with promising results.

In short, vineyard management must be tailored to local conditions, with fertilization carefully calibrated according to the vigor of the vines and taking into account weather factors such as drought, excessive rainfall, and late spring frosts.