What to Do About Fruit Cracking in Shatang Mandarin? Cause Analysis and Control Measures
Shatang mandarin, also known as: October mandarin. It originated in the area of Huaiji, Guangning and Sihui. It was first produced in Shatang Village, Huangtian Town, Sihui City, hence the name Shatang mandarin. The main production areas include: Lipu (Xiuren Town), Huaiji, Guangning and Sihui. The Shatang mandarin fruit is oblate, with a wart-like protrusion at the top and a sunken stem-end navel, orange-yellow in color, with a thin rind that peels easily. The Shatang mandarin produced in Huangtian Town, Sihui is especially delicious and extremely sweet, with no residue and a delicate mouthfeel, truly an excellent product. It is rich in vitamin C, calcium, fiber, a small amount of protein and fat, as well as abundant glucose, fructose, sucrose, malic acid, citric acid and lemon acid, plus carotene, thiamine, riboflavin, nicotinic acid, ascorbic acid, and essential elements for the human body such as calcium, phosphorus, magnesium and sodium. The Shatang mandarin tastes sweet and sour and is cold in nature, with effects such as regulating qi and resolving phlegm, moistening the lungs and clearing the intestines, and nourishing blood and strengthening the spleen.
Causes of fruit cracking in Shatang mandarin:
1. Unreasonable fertilization and imbalanced tree nutrition. For example, excessive application of phosphate fertilizer, with insufficient nitrogen and potassium, will thin the rind to a certain extent; a deficiency of trace elements such as calcium, potassium, boron, zinc and molybdenum will make the rind's toughness, elasticity and buffering capacity worse; not applying or applying little organic fertilizer, compacted soil, insufficient permeability, and poor water- and fertilizer-holding capacity also make fruit cracking more likely.
2. Imbalance of endogenous hormones in the tree, with rind and flesh development out of sync. After the fruit grows to the expansion stage, the carbohydrates and sugars in the flesh accumulate greatly and it grows faster; at this time, however, the rind epidermal cells divide little and grow slowly, causing the inner and outer growth rates of the fruit to be inconsistent. Some growers, seeing more flowering and fruit set in the early stage, use gibberellin for fruit retention at a lower concentration and fewer times, which directly affects the rind thickness in the later stage, resulting in more cracked fruit the more fruit the tree carries.
3. Weather effects: long-term drought followed by a sudden rainstorm means the root system supplies too much water to the fruit, and the flesh sacs absorb water and expand rapidly; after the rain, however, due to the structural characteristics of the rind tissue, it absorbs relatively little water, the rind cells divide and grow more slowly, and their toughness is poor, making sudden bursting extremely likely.
4. Inadequate control of diseases and pests such as canker, anthracnose, red spider mite and fruit fly causes local growth of the rind to be hindered or even damaged. Fruit cracking caused by this situation accounts for a considerable proportion.
5. Fruit cracking is also related to the condition of the tree itself. Under the same conditions, trees in full fruiting stage have a higher cracking rate than trees in young fruit stage; high-yielding trees have a higher cracking rate than trees with moderate fruiting; the top and outer parts of the canopy also have a higher cracking rate than the middle-upper part and inner branches; and trees on sour rootstock also have a higher cracking rate than trees on trifoliate orange rootstock.
Measures to control fruit cracking in Shatang mandarin:
Controlling fruit cracking in Shatang mandarin is a comprehensive technical measure. According to the various causes of fruit cracking, prevent early and prepare early, and conscientiously carry out each production link, so as to truly and effectively reduce fruit cracking and achieve high and stable yields.
1. For fertilization of Shatang mandarin, adhere to organic fertilizer as the main type and do not apply phosphate fertilizer excessively. For base fertilizer or topdressing, choose Shenshen biological organic fertilizer or Yala biological organic fertilizer; for the fruit-strengthening fertilizer, choose a compound fertilizer with medium nitrogen, low phosphorus, high potassium and containing various medium and trace elements and compound synergists, such as Yala Meijiabei 18-5-22 synergistic compound fertilizer, Entec 12-11-18 stable long-acting compound fertilizer, etc., which can moderately increase rind thickness and toughness and reduce fruit cracking. For trees with severe fruit drop in previous years, it is best to apply Yala high-end medium and trace element water-soluble fertilizer at 10 kg/mu/time, applied in spring and autumn respectively. After applying fertilizer, cover the soil well.
2. In orchards with high soil acidity (PH below 5.5), spread lime on the ground in April-May after flower drop to supplement calcium and adjust soil pH. Calcium can enhance rind strength and toughness and reduce fruit cracking. For trees with a canopy diameter below 2 m, apply 1 jin/tree; for those of 3~4 m, apply 2 jin/tree. The amount of lime applied should be based on soil pH and soil conditions; excessive lime spreading will cause iron deficiency, zinc deficiency and other nutrient deficiency phenomena in fruit trees and cause soil compaction.
3. When bearing trees enter the fruit expansion stage, high-quality foliar fertilizer should be sprayed frequently, especially in arid areas and seasons. Combined with disease and pest control, every 10-15 days, spray the leaf surface with Yala phosphorus-potassium nutrient solution or Yala sugar alcohol calcium-zinc solution at 1000-1500 times dilution, etc., foliar fertilizers containing calcium, zinc and multiple elements, to regulate the tree's nutritional balance. Spraying foliar fertilizer is simple and economical, and can effectively reduce fruit cracking while also promoting fruit expansion.
4. Strengthen water management. Cover the tree disk with grass to maintain soil moisture, balance the soil moisture supply in the tree disk, and avoid sudden drying and sudden wetting. Leaving some grass properly between rows of fruit trees can reduce water evaporation and strong sunlight radiation, and can effectively prevent abnormal fruit cracking. If there is no rain for more than 15 days during the expansion stage and drought occurs, water should be applied in time. Combined with watering, apply Yala Meijiabei solution together for better results. When starting to water, first wet the surface soil, and after two or three days, water thoroughly into the deep soil.
5. Fruit cracking occurs mostly at the top and outer part of the canopy. Therefore, combined with pruning, reasonable fruit thinning and fertilization measures, apply a fruit-strengthening and coloring fertilizer once before flower bud differentiation. This can prevent alternate bearing, and also reduce fruit without leaves and fruit at the top of bearing mother branches. Promote uniform fruiting in the middle-lower part of the canopy and inner branches, and reduce fruit at the top and outer part.
6. Reasonably spray “920” to preserve flowers and fruit, which can promote rind cell division and expansion and reduce fruit cracking. Spray after flower drop and before the peak fruit drop period, at a concentration of 20-30PPM, for a total of 2 sprays, trying not to exceed 3 times, so that the rind thickness remains in the reasonable range of 1.4-2.0 mm, resulting not only in better fruit quality, but also in very few cracked fruits and thick-rind fruits. If the rind development stagnates due to long drought without rain during the fruit expansion period, one supplementary spray of “920” or triacontanol plus 0.3% urea plus Yala phosphorus-potassium nutrient solution may also be considered, especially spraying the key parts prone to cracking before heavy rain, and the anti-cracking effect is quite obvious. However, spraying too much “920” after September will affect flower bud differentiation, reduce the number of flowers the following year, and make the current year's rind rough and loose, delay coloring, and affect fruit quality and timely marketing, so it is generally not recommended.
7. Timely control various diseases and pests to avoid fruit cracking caused by damage to the rind from diseases and pests. Fruits that have already cracked should be removed in time. This prevents cracked fruit from rotting and spreading diseases and from continuing to consume nutrients and water.