What causes fruit and vegetable cracking?

Many farmers, when discussing cracking in melons, fruits and vegetables, immediately think of calcium deficiency, and some believe that as long as calcium has been applied, the fruit will not crack. This is not the case. There are many causes of fruit cracking, involving water, fertilization, management, variety and many other aspects. Cracking triggered by calcium deficiency or imbalance is only one of the causes. A comprehensive analysis of the causes of fruit cracking and the formulation of a set of integrated anti-cracking measures are particularly important.

1. Cracking caused by the physiological characteristics of the variety

Fruit cracking is closely related to the physiological characteristics and genetic characteristics of the variety. The fruit size, peel thickness, fruit water content, cell density, fertilizer requirement pattern, sugar content and acid content, and peel development quality of the variety all affect fruit cracking.

2. Cracking caused by imbalance of plant endogenous hormones

Changes in the ratio of plant endogenous hormones affect the growth rate of the peel and the flesh. When the growth rates of the two are unbalanced, fruit cracking occurs.

In actual production, in the middle and late stages of fruit development, cracking caused by hormone imbalance is relatively common.

At the same time, the abuse of hormone-type plant growth regulators is one of the causes of fruit cracking.

In the 2011 watermelon “explosion” incident in Danyang, Jiangsu, besides being related to the planted variety and climate (drought in the early growth stage, sharp rainfall later), it was also closely related to improper use of swelling agents.

3. Cracking caused by sharp changes in soil moisture

Changes in soil moisture have a relatively large impact on the absorption of calcium in the peel. Both drought and flooding can cause water stress, reducing calcium absorption and thereby causing fruit cracking.

If drought occurs in the early growth stage of the crop and frequent rainfall occurs during the rapid fruit expansion stage, the water transported by the root system to the fruit increases sharply, and the flesh cells expand rapidly. At this time, however, the peel has mostly aged, and the peel cells expand slowly due to the restriction of the cuticle, resulting in the flesh bursting the peel.

Cracking caused by this situation is relatively common in grapes, jujubes and pomegranates. If there is a lack of water in the early stage, it will affect the expansion of young fruit. If continuous rainfall or flood irrigation occurs during the coloring stage, it will cause a major outbreak of cracking.

4. Cracking caused by pests and diseases

Studies have shown that anthracnose can cause cracking in navel oranges. Anthracnose, rust mites, red spiders and other damage are directly related to cracking, and attention must be paid to the prevention and control of pests and diseases.

After powdery mildew damages grapes, the peel hardens and loses elasticity, and after the pit-hardening stage it easily splits longitudinally from the top of the fruit, forming cracks.

After red spiders damage grapes, brown rust spots form on the fruit surface, and most split longitudinally from the fruit stalk, forming cracks.

5. Cracking caused by nutritional imbalance

The mineral elements in the flesh and their nutritional balance have a significant impact on fruit cracking. Imbalance of nutrients in the tree body will aggravate fruit cracking.

During fruit growth, phosphorus, potassium and calcium have the greatest impact on fruit cracking, followed by magnesium, boron, zinc, iron, copper and manganese.

When one or several elements are excessive while the content of other elements is relatively low, cracking will increase.

In actual production, in the late growth stage of crops, cracking caused by calcium deficiency and excessive potassium is very common.

At present, the problem of soil acidification is becoming increasingly prominent. The resulting deficiency or imbalance of medium and trace elements is very common, which aggravates the degree of fruit cracking.

6. Cracking caused by cultivation and management measures

Orchards with weak tree vigor, poor light, poor ventilation and excessive nitrogen fertilizer application have severe fruit cracking.

Fruits and vegetables with a large load and a small leaf-to-fruit ratio are prone to cracking.

Orchards with poor soil drainage, severe compaction, poor permeability and soil acidification have severe fruit cracking.

Orchards with poor pest and disease control have relatively severe fruit cracking.

In orchards that use large amounts of ethephon, gibberellin and 2,4-D, the amount of fruit cracking rises significantly.

In summary, the causes of fruit cracking are many-sided, and solving the problem should also comprehensively consider many factors. One-sided emphasis on a single factor often makes it difficult to achieve good results. It is necessary to summarize a relatively mature integrated anti-cracking management plan. The plan involves the control of soil pH and comprehensive nutrient content, water management, pest and disease control, and the use of growth regulators, so as to achieve the goal of preventing cracking.