How to prevent and control fruit cracking in pomegranates during the ripening period? A detailed guide to practical methods

1. Plant crack-resistant varieties

This is the fundamental measure for preventing fruit cracking. Priority should be given to this measure when developing pomegranates. Among the excellent pomegranate varieties, Heyin Tonghongdeng pomegranate, Heyin Yueliangbai pomegranate, Heyin Hongdeng pomegranate, Tunisian soft-seed pomegranate and Chaodazi pomegranate are all crack-resistant. Taishanhong pomegranate is also relatively crack-resistant, though its quality is not as good as the above varieties. However, Lintong Tianhongdan, Dahongtian, Fenhongtian, Yushiliu No. 1, Yushiliu No. 2 and Yushiliu No. 3 are all not crack-resistant. In pomegranate orchards where crack-prone varieties have already been planted, the varieties can be replaced with crack-resistant ones through top grafting.

2. Choose high, dry terrain for growing pomegranate trees

Practice has proven that on high, dry terrain, fruit cracking is mild; on low-lying, waterlogged terrain, fruit cracking is severe.

3. Apply more organic fertilizer and complete fertilizer

Such pomegranate trees crack very little or not at all. Pomegranate trees given fertilizer specially formulated for fruit trees also crack less, whereas pomegranate trees given excessive nitrogen fertilizers such as ammonium bicarbonate and urea crack severely. Therefore, when fertilizing pomegranate orchards, priority should be given to high-quality farmyard manure, such as cow manure, sheep manure, chicken manure, pigeon manure, horse manure, pig manure, straw manure and various green manures. Even when applying chemical fertilizers as a top dressing, it is best to choose a compound fertilizer specially formulated for fruit trees or a high-quality compound fertilizer containing the three elements nitrogen, phosphorus and potassium. Especially in the later stage of fruit development, never apply nitrogen fertilizer as a top dressing.

4. Pay attention to watering and water control

In the early stage of pomegranate fruit development, from May to July, when the weather is dry, water promptly to promote fruit cell division. However, about 1 month before ripening, as long as the weather or soil is not excessively dry, try not to water; even if it is excessively dry, water only lightly. Watering before ripening is an important cause of pomegranate fruit cracking; especially when there is drought early on and then heavy rain or heavy watering later, cracking is even more severe.

5. Spray calcium on the trees

During the growth and development of pomegranates, spraying calcium chloride, calcium nitrate or other organic calcium fertilizers 2 to 3 times all help reduce fruit cracking, with obvious results. However, they cannot completely eliminate cracking.

6. Bag the fruit

Bagging is a relatively good way to prevent fruit cracking. Double-layer special fruit bags (such as Japanese Kobayashi apple-specific bags) give the best results, and plastic film bags also work fairly well. Bagging must be completed before June 1. Before bagging, spray the whole tree carefully once with an 800-fold dilution of Daconil M-45 fungicide mixed with a 2000-fold dilution of 25% chlorbenzuron No. 3, to eliminate pomegranate fruit pathogens and pests such as the peach fruit borer.

7. Rain-shelter cultivation

Build a rain shelter over the upper part of the orchard, but allow air to enter on all sides. This is a very good way to prevent fruit cracking, and is especially suitable for growing precious varieties with particularly high economic value.

8. Harvest at the right time and harvest early

The ripening period of pomegranates is as early as mid-August for early varieties and as late as mid-October for late ones. Therefore, harvest at the right time according to the ripening period of each variety. Because pomegranate seeds never stop growing and developing before leaf fall and grow larger every day, if harvesting is too late, even crack-resistant varieties will develop cracking. For varieties that are not crack-resistant, harvest at the right time or early. Although early harvesting lowers quality, it is a last resort; early harvesting is always better than late harvesting.

9. Keep the tree vigor moderate and robust

Practice has proven that pomegranate trees with moderate, robust vigor crack mildly, whereas excessively vigorous pomegranate trees crack severely. This should be achieved through various cultivation measures such as improving the soil, regulating fertilizer and water, and pruning and training.