Detailed Explanation of Key Technical Points for Soil, Fertilizer and Water Management in Apple Orchards

1. Soil management

For the soil management of mature fruit tree orchards, the clear-root method or tree-disk mulching method should be adopted. From spring to before the rainy season each year, after combining fertilization and irrigation, carry out intertillage and loosening of the soil. Weed 1-2 times to keep the soil loose and free of weed growth. In the rainy season, cut grass and cover the tree disk 1-2 times. In autumn, after the fruit trees shed their leaves, carry out autumn plowing. Use an iron shovel to deep-turn the tree disk to 15-20 cm, then apply additional organic fertilizer. Apply topdressing three times, respectively before and after sprouting, after flower drop, and during the fruit enlargement stage, using nitrogen, phosphorus and potassium elements in combination. The ratio is 1:0.6:1.5.

2. Fertilizer management

① Apply more organic fertilizer, especially green manure and other organic fertilizers rich in phosphorus and potassium. This can not only increase fruit tree yield, but also improve fruit coloring and enhance fruit flavor and storage performance.

② Apply nitrogen fertilizer reasonably: appropriately increasing nitrogen fertilizer has a clear promoting effect on fruit tree growth and fruiting. However, improper application of nitrogen fertilizer also has various adverse effects on fruit quality. Therefore, high-quality fruit must involve rational application of nitrogen fertilizer. Generally, nitrogen fertilizer for fruit trees should be controlled to a level at which the tree's nitrogen nutrition level is slightly lower than or slightly limiting to yield. If the highest yield level is reached, fruit coloring and quality will be poorer. It is best not to apply ammonium nitrogen fertilizer around the flowering period, so as to avoid insufficient calcium uptake by the fruit and reduced quality.

③ Apply more phosphorus and potassium fertilizer: a large number of trials show that appropriately increasing phosphorus and potassium fertilizer can increase fruit color, raise fruit sugar content, improve fruit quality, and also increase fruit size. Applying potassium fertilizer alone tends to reduce fruit firmness and storage life, while applying phosphorus and potassium together has not been found to cause adverse phenomena. Therefore, in each region, according to soil available phosphorus and potassium, the ratio of fertilizer to nitrogen fertilizer should generally reach 1:1:1. Each year, combine base fertilizer and topdressing with irrigation 2—3 times, and combine with pesticide spraying for foliar topdressing.

④ Supplement nutrition for deficiency symptoms: when a certain nutrient element is insufficient in fruit trees, nutritional imbalance occurs and deficiency symptoms appear, affecting fruit tree growth, fruiting and fruit quality. For example, boron deficiency causes fruit shrinkage disease, calcium deficiency causes bitter pit, water core and other storage diseases, zinc deficiency causes little leaf disease, and iron deficiency causes chlorosis. All of them directly or indirectly reduce fruit quality, and should be prevented and treated promptly according to specific conditions.

For most deficiency symptoms, the first control approach is to increase soil organic matter, apply more green manure and farmyard manure; pay attention to crop rotation and stubble replacement; maintain appropriate soil moisture; adjust soil pH to near neutral; and directly apply the lacking elements to the soil and foliage.

⑤ Adjust the ratio of various nutrient elements: various elements often have mutually restrictive and mutually promoting effects. Some deficiency symptoms are often caused by imbalance among various elements, so attention must be paid to adjusting the proportional relationships among various nutrient elements. Generally, when the nitrogen-potassium ratio is between 0.4-0.6, fruit flavor and coloring are better. When the nitrogen-calcium ratio in the fruit is 10, quality is very good, and storage performance is also best. If it is greater than 20, bitter pit will occur; if greater than 30, the fruit is soft and not storage-resistant. Therefore, when preventing and treating a certain deficiency symptom to improve fruit quality, attention must be paid to adjusting the proportional relationship with other elements in order to achieve the expected effect.

3. Maintain suitable soil moisture

Suitable water supply is a basic condition for improving fruit quality. When water is insufficient, not only is the fruit small, but the flesh also becomes coarse and hard, and quality declines significantly. When there is too much water, sugar content decreases and acid content increases. When drought and waterlogging are uneven, physiological diseases such as fruit cracking, sunscald and water core often occur. From the beginning of fruit coloring to before fruit harvest, water should be properly controlled, and waterlogging should be drained, otherwise quality will decline. During high-temperature summer periods, appropriately spraying water to lower temperature also helps improve quality.