What causes apples to fail to color after bag removal?
It is currently the peak season for apples to hit the market in large quantities, and it is the harvest season for fruit growers. To ensure yield and quality in apple cultivation, bag removal techniques are now mostly adopted. However, recently some fruit growers have found that their apples do not color after bag removal, and some even show a regreening phenomenon, leading to a lower marketable rate. So what causes apples to fail to color after bag removal? Let's find out together.
1. Unreasonable fertilizer application
In fruit tree fertilization, it is advocated to mainly use high-quality organic fertilizer, supplemented by chemical fertilizer, and then combine it with an appropriate amount of trace elements. Only in this way can the tree's nutritional supply be comprehensive, avoiding the deficiency of a certain element and affecting the final yield and quality. However, in actual practice, many fruit growers, influenced by traditional thinking, tend to apply excessive nitrogen fertilizer, causing excessive vegetative growth, a large number of shoots to sprout, and, combined with improper pruning, resulting in poor ventilation and light penetration in the fruit tree. For bagged apples, under poor light transmission conditions, their chlorophyll content is relatively low, so after bag removal, when the fruit is exposed to light, the chlorophyll exchange rate accelerates, resulting in a regreening phenomenon. In this case, fertilization must be scientific and reasonable: emphasize nitrogen fertilizer in the early growth stage, apply phosphorus and potassium fertilizers in combination during the middle growth stage, and emphasize phosphorus and potassium fertilizer application in the later stage while reducing nitrogen fertilizer application.
2. Inadequate pruning
Generally, orchards where regreening occurs after bag removal often show a closed canopy with no light penetration, which is mostly caused by a large number of shoots sprouting, high planting density, and dense branches. Apart from improper fertilization, another cause is inadequate pruning of the plants, which leads to increasingly dense branch growth. Therefore, timely pruning is necessary. Pruning should focus on creating a good fruiting tree shape and a good ventilation and light transmission environment, which is conducive to fruit coloring.
3. Fruit bag selection and quality assurance
Since the promotion of fruit bagging technology, 90% of apple production in China has adopted bagging technology, and production costs have also increased. As the apple cultivation area has increased year by year, the bagging model has been widely promoted. Many fruit growers, in order to reduce planting costs, choose cheap and inferior fruit bags, or because market demand for fruit bags is large, a large number of manufacturers have entered the market, and the quality of the fruit bags produced is uneven. When fruit growers choose lower-quality fruit bags, they end up with fruit that looks unattractive and has a greenish color. Therefore, when choosing fruit bags, multiple factors should be considered, ensuring that the bags can withstand wind, sun, and rain without splitting, have strong shading performance, do not leak water, and have good air permeability.
4. Poor timing of bag removal
The timing of bag removal for apples is also quite important. Many fruit growers, in order to seize the market first, often remove bags 10-15 days early, which shortens the fruit's growth time inside the bag, causing the fruit to fail to fully lose its green color or to lose it poorly, resulting in a green head phenomenon similar to regreening. Also, if the weather is not good and light conditions are poor during bag removal, regreening may occur after bag removal. In this case, fruit growers should strictly follow the established bag removal time to avoid removing bags too early or too late.
The above is an introduction to what causes apples to fail to color after bag removal. We hope it can help you. To learn more related knowledge, please stay tuned to us.