Causes and treatment of apple yellow leaves
Yellowing of apple leaves is a common cultivation problem for fruit farmers. It not only affects the photosynthesis efficiency of fruit trees, but also directly reduces fruit quality and yield. This article analyzes three typical yellow leaf inducements from a professional perspective, and systematically explains the solution based on 20 high-definition schematic maps to help you quickly diagnose and restore the health of fruit trees. Key incentives and scientific countermeasures for apple yellow leaves are unbalanced in light management. When the crown closure exceeds 70%, the light intensity of the inner chamber leaves is less than 30% of the natural light when the yellow leaves are in densely planted orchards. Studies have shown that when the average daily light of leaves is less than 3 hours, the chlorophyll content drops by 5-8% per week. It is recommended to use improved spindle pruning, keep the main branch opening angle of 55-65 degrees, and ensure that the crown light transmittance reaches more than 40% after pruning. Special attention should be paid to the thinning of overly dense fruiting branches, and the number of fruiting branches retained per square meter should be controlled at 12-15. When the pH of soil with iron metabolism disorder chlorosis is>7.5, the availability of iron decreases by 85%. Typical symptoms are yellowing at the top of the new tip and a network of chlorosis between the veins. It is recommended to use a combination of EDDHA iron chelate (concentration 0.1%)+ humic acid (500 times liquid) spray, combined with ditch application of sulfur powder (3kg/plant) to adjust soil pH. The important spraying period is selected from 9 to 11 when the stomatal opening is the largest, and the front and back sides of the leaves are evenly coated with the medicine. The annual nitrogen requirement of yellow-leaf apple trees with unbalanced nutrient supply during the full fruit period is about 150-200g/plant, and the flowering period to young fruit period accounts for 60% of the annual demand. It is recommended to adopt the "four-stage" fertilization method: germination period (high-nitrogen type), flower bud differentiation period (high-phosphorus type), fruit expansion period (high-potassium type), and post-harvest (organic fertilizer + medium and trace elements). When symptoms of fertilizer removal are found, emergency supplementary amino acid water-soluble fertilizer (800 times solution) combined with 0.3% potassium dihydrogen phosphate is applied once every 7 days for three times in a row. The comprehensive prevention and control system for apple yellow leaves establishes a three-dimensional early warning system that includes soil testing (twice a year), leaf analysis and diagnosis (long-term sampling of new shoots), and meteorological monitoring (focusing on monitoring continuous rainy weather). Combining grass cultivation (mainly white clover) to improve the microecology of the orchard can reduce the incidence of yellow leaves by more than 60%. The key prevention and control period will focus on the two core nodes of spring pruning (February-March) and autumn base fertilizer application (September-October).
By implementing comprehensive measures of precise nutritional management, optimizing tree structure and improving the rhizosphere environment, the incidence of apple yellow leaves can be effectively controlled below 5%. It is recommended to establish an orchard health record to record each treatment measure and effect feedback, and gradually form a personalized management plan suitable for local climate conditions.