What to do about uneven berry size in grapes? What prevention and control measures are there?

Grapes are a widely loved fruit and are widely cultivated, but during their growth they are prone to uneven berry size, which affects economic returns, so what should be done about this situation? What prevention and control measures are there? First you need to understand what causes this situation.

I. Causes of uneven berry size in grapes

1. Uncontrolled fertilizer and water management: too much nitrogen fertilizer applied and too large a water supply.

2. The plant's load is light and has not reached the corresponding yield, and the shoots grow excessively.

3. Applying only chemical fertilizers and neglecting the application of organic fertilizer.

4. Pinching the tips and breaking off the vines too early during the flowering period, leaving too few leaves.

5. During the flowering period the trellis surface is dense and there are many branches, causing poor ventilation and light penetration at the trellis surface during flowering, resulting in flower abortion, a low fruit-setting rate, and loose, scattered clusters.

6. Single or double vines of the plant are too short and the trellis surface is too low, both of which cause the plant to grow vigorously, especially in grafted seedlings.

II. Prevention and control measures

1. Control water: before flowering, the soil 10 cm below the surface should form a ball when grasped by hand; generally 2 waterings before flowering, or 1 watering in low-lying areas or heavy clay soil, or irrigation.

2. Control fertilizer: before flowering, apply little or no nitrogen fertilizer; apply organic fertilizer. When the berries are set and grow to the size of a large soybean, heavy fertilizer and heavy water are needed. From the pit-hardening stage to the coloring stage, more phosphorus and potassium fertilizer should be applied.

3. Reasonably adjust the plant load: for grapevines 4 years and older, about 10 kg is appropriate; at flowering, fruiting branches should be at least 20 cm long; those exceeding 20 cm in length and 1 cm in thickness should retain double clusters, especially at the bends of the vertical trellis and on strong shoots at the tips, where double clusters or double branches with a single cluster should be retained to press the branch.

4. Reasonable pruning: strong branches (referring to branches 1.2 cm thick and above) within 25 cm of the fruiting branch distance should be thinned out; where the fruiting branch distance exceeds 20 cm, multi-bud pruning should be adopted to fill the empty spaces. When bud rubbing and shoot thinning in the following spring, keep the two ends and remove the middle. The branch distance must be well controlled; at a branch distance of about 25 cm, retain 3 buds when pruning. When rubbing buds and thinning shoots in the following spring, rub off the terminal bud and retain 1-2 buds. Strong fruiting branches retain double clusters; fruiting branch distances of 15-20 cm retain the basal bud and the rest are rubbed off, so as to maintain a moderate tree vigor.

5. Pinching tips and breaking vines: the time for pinching tips and breaking vines should not be too early; 3-5 days before flowering is appropriate. For double-bud fruiting branch groups, when pinching tips, retain a long and a short one: short branches 6-8 leaves, long branches (strong branches) 8-10 leaves. For clusters 10 cm long, pinch or pinch less; at about 20 cm, pinch off 1/5.

6. Cutting off surface roots: for Kyoho grapevines 4 years and older that have developed uneven berry size, the surface roots need to be cut off. The method: before taking the vines down in autumn, cut the surface roots cleanly with a shovel; the root-cutting distance from the base of the plant should not exceed 10 cm, otherwise it will not be effective. After root cutting, growth is slightly slower in spring and leaves turn yellow; fertilizer and water management need to be strengthened to quickly restore tree vigor.

7. Twisting branches: 3-4 days before flowering, twist and bend or twist flat the upper part of the cluster on overly strong fruiting branches.

8. Using secondary branches to bear fruit: when the grapes are nearly the size of soybeans and uneven berry size is already clearly visible, cut off the upper branches and leaves at the 5-6 leaf position and use secondary branches to bear fruit. This should be done before June 20; it is appropriate and gives a high fruit-setting rate, neat clusters, and a maturity period 7-10 days later.

9. Using swelling agents: when uneven berry size is already clearly visible in Kyoho grapes (about 15 days after flowering), dip the clusters once (or spray evenly). If the berries have elasticity, then by the coloring stage, if cracking is found, water should be controlled in time or drainage done after rain.

10. Using the new-type tree growth promoter-controller PBO: it has the characteristics of promoting larger grapes, true color, early maturity, crack prevention, and increased yield. The dosage should be determined according to tree vigor. The first time, 1-2 days before flowering, apply to the soil; for vigorous trees, watering application is suitable, 5-7 g per plant; for strong trees, 2.5-3 g per plant; for trellis frames, about 250 g per mu, and for hedge frames 250-500 g. The second time, about 25 days after flowering, spray; the spray concentration is 100-250 times. Practice has proved that using PBO on vigorous Kyoho trees significantly increases fruit set. For the needed nitrogen control, apply urea by watering in early April, 100-150 g per plant; at germination, add urea along with pesticide spraying; in mid-June, potassium fertilizer is mainly used as foliar fertilizer; for continuous harvesting, immediately apply topdressing fertilizer twice and irrigate; from late September to early October, apply more than 3000 kg of farmyard manure and irrigate twice.