With the autumn harvest just around the corner, have you prepared your fruit trees with post‑harvest fertilizer?

During the annual cycle of fruit trees, the accumulation and consumption of nutrients follow a distinct pattern, which is particularly pronounced in deciduous fruit trees.

         During the early stages of vegetative growth, the development of roots, shoots, leaves, flowers, and fruits requires substantial nutrient supply, with consumption‑driven metabolism predominating. In the latter half of the growing season, as the leaf canopy develops and photosynthate production increases, the accumulation of nutrients exceeds their consumption, shifting the plant to storage‑oriented metabolism. These two metabolic modes are mutually foundational and reinforce one another.

         During the early growth stage, fruit trees primarily rely on stored reserves for their nutrient needs. Relying solely on the tree’s own reserves in the later stages is insufficient, which will inevitably compromise next year’s vegetative growth, flowering, and fruit set. Therefore, the application of base fertilizer is critically important.

         However, even when the same fertilizer is applied in the same quantity, differences in application timing can lead to significant variations in effectiveness. Hence the saying: “Fertilizing in autumn is gold; fertilizing in winter is silver; fertilizing in spring is wasted effort.”

Why should base fertilizer be applied in autumn?

         1. From early spring bud break through flowering and fruit set, the nutrients consumed by fruit trees are primarily those stored in the tree’s tissues from the previous year. The period between harvest and leaf fall is the optimal time for nutrient accumulation, and applying a base fertilizer in autumn can enhance the tree’s nutritional reserves.

         2. During the winter and spring, low temperatures slow the decomposition and maturation of organic fertilizers, limiting their effectiveness when applied during these periods. By the time the fertilizer has fully decomposed and released its nutrients, it often triggers a second flush of shoot growth in fruit trees, which can negatively affect flower bud differentiation and fruit set. In contrast, autumn is a critical phase for nutrient accumulation in fruit trees: aboveground growth has largely ceased, while leaf photosynthesis remains vigorous, facilitating the efficient translocation of stored reserves to stems and branches.

         3. Applying base fertilizer in autumn can increase soil porosity, loosen the soil, enhance the orchard’s ability to retain moisture and store water, help prevent drought during winter and spring, and also raise soil temperature, thereby protecting fruit tree roots from frost damage.

         4. Autumn represents the final peak period of root growth in the year, characterized by vigorous physiological activity and strong nutrient uptake. It also helps delay leaf senescence, enhance the photosynthetic capacity of autumn leaves, and increase the tree’s reserve nutrient storage.

         5. In autumn, soil temperatures are relatively high and soil moisture conditions are favorable, promoting vigorous microbial activity. Consequently, applied organic fertilizers decompose rapidly and are readily absorbed and utilized by the root system. Moreover, under microbial action, organic matter is transformed into humus, increasing the soil’s organic matter content, enhancing its aggregate structure, and improving its permeability as well as its capacity to retain nutrients and water. This also raises soil temperature, creating an optimal growing environment for fruit tree roots, ensuring normal growth and development, and fostering high, stable yields while enabling early economic returns.

         6. Applying base fertilizer in autumn helps balance vegetative and reproductive growth. After the readily available nutrients in the fertilizer are absorbed, they significantly enhance the functionality of autumn leaves, promoting greater nutrient accumulation and resulting in well‑filled flower buds. This leads to earlier bud break in the following spring, more uniform flowering, vigorous spring shoot growth, and increased overall growth—conditions that support a robust tree vigor conducive to high yields and superior fruit quality. Meanwhile, the slow‑release nutrients undergo prolonged decomposition and maturation in the soil, becoming readily available for uptake in spring, thereby strengthening late‑season spring shoot development, improving the quality of medium‑ and short‑length shoots, and enabling timely cessation of elongation, thus creating favorable conditions for flower bud differentiation.

         7. Improve the root‑zone environment and enhance the tree’s stress tolerance. Combined with autumn fertilization and deep soil tillage, this approach can optimize soil structure, improve soil aeration, promote root respiration and growth, and strengthen the soil’s capacity to retain water and nutrients while providing protection against cold during winter.

         8. Autumn is the peak growing season for fruit tree root systems; fertilization during this period allows any minor root injuries to heal quickly and stimulates the rapid development of new roots, thereby increasing the number of absorptive roots, expanding the area available for nutrient uptake, and significantly enhancing fertilizer use efficiency.

Specific methods for applying base fertilizer in autumn

         Fertilization timing

         Generally, the optimal time for applying fertilizer is from after fruit harvest until before autumn leaf fall—right now is the ideal period. During this window, it’s best to apply base fertilizer as early as possible rather than delaying. After harvesting, the sooner base fertilizer is applied, the more conducive it is to restoring tree vigor, promoting the full development of shoots and buds, and enhancing both the quality and quantity of flower buds. For vigorously growing or overly vigorous trees, application can be slightly delayed; for weak trees or those bearing a heavy crop, it should be advanced accordingly.

         Types and amounts of base fertilizer applied

         The primary type of base fertilizer is typically slow-release organic fertilizer, such as humic acids, compost, stable manure, barnyard manure, farmyard manure, compound fertilizers, green manures, crop residues, weeds, and plant branches and leaves. These are supplemented with quick‑acting chemical fertilizers and micronutrient fertilizers, and combined with microbial fertilizers, to achieve a balanced and complementary mix of slow‑release and fast‑acting nutrients.

         In fertilizer application, nitrogen, phosphorus, and potassium should be balanced; however, excessive use of quick‑acting nitrogen fertilizers should be avoided to prevent excessive vegetative growth at the tips of branches and the development of winter shoots, which can hinder the accumulation of stored nutrients in fruit trees and compromise the quality of flower buds.

         Fertilization method

         In production, deep tillage for soil improvement is often combined with fertilization methods such as ring‑shaped trench application, radial trench application, and band‑fertilization.

         Ring trench application method ： Dig a circular trench 50 cm deep and 50 cm wide along the outer edge of the tree crown’s vertical projection, mix the fertilizer thoroughly with soil, apply it to the trench, and promptly cover it to seal the trench. This method is commonly used for young trees.

         Radial trench application method: Starting 1 meter from the tree trunk, dig 4 to 8 radial fertilizer trenches extending outward, each reaching 50 cm beyond the outer edge of the tree canopy. The trenches should be 15 cm deep near the trunk and gradually deepen to 50 cm toward the outer edge. This method is suitable for mature fruit trees.

         Furrow fertilization method: On the two opposite sides slightly outside the tree canopy, dig trenches approximately 50 cm deep and 50 cm wide; the trench length should be determined according to the size of the canopy. When applying fertilizer, rotate the application sites annually. This method is commonly used in densely planted orchards.

         Precautions

         When applying farmyard manure, it must be fully composted. The fertilization sequence is to apply organic fertilizer and bio‑fertilizer first, then backfill with topsoil before applying compound fertilizer and micronutrient fertilizers. Water application should also be coordinated; combining irrigation with fertilization further enhances fertilizer efficiency.