Common Fertilization Mistakes for Fruit Trees and Field Crops and What Are the Correct Fertilization Methods

At present, farmers' cultivation level is relatively low, especially in fertilization, where there are many mistakes and improper fertilization easily occurs, resulting in poor fertilizer efficiency, slow results, and even plant death. So what should be noted during fertilization? What fertilization methods are there for fruit trees and field crops?

Fertilization Mistakes

Mistake 1: The closer fertilization is to the plant stem, the more easily the fertilizer is absorbed

This is a fairly common phenomenon in rural areas, and this fertilization method is quite harmful. Because the part of the plant that absorbs nutrients is the root hair zone, the plant stem and roots (except the root hair zone) absorb very few nutrients or none at all. The closer fertilization is to the plant stem (except at the seedling stage), the farther the fertilizer is from the plant's nutrient-absorbing area, so the less easily it is absorbed. If too much fertilizer is applied and the concentration is too high, fertilizer burn on seedlings is likely to occur. Therefore, when fertilizing, the fertilization position should be determined according to the aboveground growth of the plant and the underground root growth, so as to ensure the fertilization effect.

Mistake 2: Fertilizing only after crops show signs of nutrient deficiency

After fertilizer is applied, it takes 3-5 days in paddy fields before it can be absorbed and used by crops, and generally 5-7 days in dry land before it can be absorbed and used. Therefore, if fertilization is carried out only after crops show signs of nutrient deficiency, it will prolong the period of crop nutrient deficiency and cause reduced yield. So fertilization work should be carried out according to the fertilizer requirements of the crops: apply fertilizer 5-7 days in advance in paddy fields and 8-10 days in advance in dry land. At the same time, nutrient absorption by crops is also related to light, temperature, water, and fertilization methods (such as dry application, drenching application, and foliar topdressing). Strong light, high temperature, and sufficient water accelerate crop nutrient absorption; conversely, absorption slows down. Because foliar topdressing allows nutrients to be directly absorbed by leaves, it takes effect quickly and can be applied later, but the concentration must be low to prevent leaf damage. Drenching application allows fertilizer to directly seep into the plant roots, takes effect relatively quickly, and can also be appropriately delayed. Dry application has slow fertilizer efficiency and should be applied early.

Mistake 3: As long as crops have good vegetative growth, high yield can be obtained

Crop growth includes two stages: vegetative growth and reproductive growth (except for leafy vegetables and fleshy-stem crops). Applying sufficient nitrogen fertilizer in the early growth stage can promote vegetative growth, but if nitrogen fertilizer is excessively applied during the reproductive growth stage, it will cause crops to remain green, affect reproductive growth, hinder the transformation of nutrients, and instead reduce yield and lower quality. Therefore, fertilization should be carried out according to crop growth conditions: mainly nitrogen fertilizer in the early stage to promote vegetative growth, and combined application of nitrogen, phosphorus, and potassium in the middle and late stages to promote reproductive growth and increase yield.

Mistake 4: As long as sufficient fertilizer is applied, high yield can be obtained

The types and amounts of nutrients required by various crops during the whole growth period and at different growth stages are all different. If fertilization is not carried out according to the fertilizer requirements of the crops, first, crops will show nutrient deficiency symptoms, and stress resistance and disease resistance will decline, resulting in reduced yield and lower quality; second, nutrients that some crops need in small amounts or basically do not absorb will remain or be lost, causing fertilizer waste. Therefore, the type and amount of fertilizer should be determined according to the growth characteristics of the plants so as to give full play to fertilizer efficiency.

Mistake 5: As long as fertilizer is applied, there will be fertilizer efficiency

The fertilizer efficiency of fertilization is related to many conditions such as soil characteristics, crop nutrient absorption characteristics, fertilizer nutrient release characteristics, and water, air, and heat. If the influence of various factors is not fully considered, nutrient loss, nutrient deficiency, and other phenomena are very likely to occur. Sandy soil has fast fertilizer efficiency, but loss is also fast, so it should be applied according to the principle of less each time and multiple applications. Clay loam has slow fertilizer efficiency, so sufficient base fertilizer should be applied and topdressing should be applied early. Potassium fertilizer has good solubility, but loss is also fast, so it should be applied in a timely manner according to the potassium requirements of the crops. Organic fertilizer and phosphate fertilizer have slow fertilizer efficiency and less loss, so they should be applied early. Ammonium bicarbonate is highly volatile and can be composted with organic fertilizer or phosphate fertilizer for 1-2 days before application, which can reduce nutrient loss.

Mistake 6: Focusing only on the amount of fertilizer applied, not on nutrient content

Some compound fertilizers currently on the market are widely used in rural areas because of their relatively low unit price. These compound fertilizers generally have low effective ingredient content, or the content of one of the three major elements is very low or completely absent. However, farmers do not pay enough attention to these situations and still follow the fertilization habits used for high-content compound fertilizers. As a result, the nitrogen, phosphorus, and potassium applied are insufficient, causing crop nutrient deficiency and nutrient deficiency symptoms, affecting yield and quality. Therefore, when using these compound fertilizers, it is necessary to fully understand their nitrogen, phosphorus, and potassium contents and, according to the fertilizer requirements of various crops, use single-element fertilizers such as nitrogen, phosphorus, and potassium in combination to ensure normal crop growth.

Mistake 7: The more fertilizer applied, the higher the benefit

According to the law of diminishing returns, after fertilization reaches a certain amount, the input-output ratio declines and benefits decrease. If too much fertilizer is applied, it will cause reduced yield. Therefore, according to the fertilizer requirements of the crop throughout the growth period, soil fertility, crop planting density, and so on, the best fertilization plan should be found and applied on the principle of sufficient supply without waste, so as to give full play to fertilizer efficiency and increase economic benefits.

Mistake 8: Focusing only on applying major elements, not on applying trace elements

Major elements are the basic elements on which crops depend for growth, but some crops need relatively more of a certain trace element during the whole growth period or at a certain growth stage, or the soil lacks trace elements. If trace elements are not added, plant deformity, flower and fruit drop, and reduced product yield and quality will occur. Therefore, while applying sufficient major elements such as nitrogen, phosphorus, and potassium, it is necessary to apply multiple trace elements such as iron, manganese, zinc, and boron in combination according to the fertilizer requirements of the crops and the soil nutrient composition, so as to ensure normal crop growth.

Mistake 9: Applying only base fertilizer, not topdressing

Nowadays many users, fearing trouble, stop topdressing after applying base fertilizer. This fertilization method is unscientific. Crops need relatively few nutrients in the early stage, and applying sufficient base fertilizer can indeed guarantee the crop's nutrient needs for a long time. But even for fertilizers with relatively strong residual effects, the duration of fertilizer efficiency is limited. Especially for soil with poor fertilizer and water retention capacity, failure to topdress in time makes nutrient depletion more likely. Therefore, crops with a growth period exceeding 2 months should be appropriately topdressed to ensure the crop's nutrient needs during the vigorous growth period.

Mistake 10: Fertilizing fruit trees based on flowering

How many flowers a fruit tree has depends to a large extent on tree vigor. To make fruit trees differentiate more flower buds and set more fruit the next year, sufficient fertilizer should be applied the previous year, especially post-harvest fertilization, which is very important, because after fruit picking the fruit tree is greatly weakened. At this time, nutrients should be supplemented in time to restore the fruit tree's vigor, enhance its resistance, and ensure its production capacity the next year. Some people like to apply winter fertilizer. Although it is useful, it is not the best timing, because the most important part for fruit trees to absorb nutrients is the roots. When winter begins, the tree's root system is almost dormant, and its ability to absorb nutrients is very weak. The best time to fertilize fruit trees is after fruit picking and before leaf fall. The most direct result of fertilizing based on flowering is an obvious alternate bearing phenomenon in fruit trees.

Mistake 11: Same formula, same dosage, same effect

The reasoning is simple. The main difference between a fat person and a thin person is not how much they eat, but how much they absorb. The same is true of fertilizers. With the same formula and the same dosage, there will be an obvious difference in nutrient utilization rate due to the product itself. This is why some compound fertilizer products with a total nutrient content of 40% can have better effects than other products with 45% nutrients.

Mistake 12: High price = high cost

Because compound fertilizer products belong to the category of means of production, not direct consumer goods, the basis for analyzing whether the cost is high or low is not price but the input-output ratio. If, under the same dosage or the same input, a product brings higher benefits and higher yield, then that product's cost is lower.

Mistake 13: After using compound fertilizer, no other fertilizer is needed

Some users believe that after applying compound fertilizer, there is no need to apply other chemical fertilizers. This is wrong. Generally, compound fertilizers commonly contain only nitrogen, phosphorus, and potassium, and a small number of varieties contain zinc and boron. If timely supplementation of effective medium and trace nutrient elements is not given attention, crop yield will likewise be affected.

Mistake 14: The faster the fertilizer dissolves, the better

Crops' need for nutrients is just like people's: they need them every day, and their absorption capacity is also limited. If it dissolves quickly but the crop cannot absorb it, that is waste. Therefore, the nutrient release rate of a good-quality fertilizer should correspond to the crop's nutrient needs. This is also the main reason why some products add slow-release agents: to ensure the crop's nutrient needs throughout the whole process. But the author believes that chemical fertilizers with slow-release agents are not suitable for topdressing, because if the nutrient release rate cannot keep up with the crop's nutrient needs, early crop nutrient deficiency will occur.

Mistake 15: Excessive nitrogen fertilizer in topdressing

Many users excessively apply nitrogen fertilizers such as ammonium bicarbonate and urea during topdressing. Although this produces an obvious effect on crop growth, it does not bring users an increase in yield, because nitrogen is very important for early crop growth, but as the crop grows, the demand for phosphorus and potassium becomes higher and higher, while the need for nitrogen instead decreases. Excessive nitrogen application will only make crops grow excessively. Therefore, to ensure a yield increase effect, attention should be paid to topdressing with compound fertilizer.

Mistake 16: If yield does not go up, the fertilizer is bad

A small number of users believe that if yield does not go up, it is the fertilizer's fault. In fact, there are many reasons why yield does not go up, such as weather, soil quality, fertilization methods, selection of fertilizer product formulas, seeds, pesticides, and field management. It should be examined from all aspects; whether the fertilizer is good or bad is only one of the factors.

Common Fertilization Methods

I. Fruit tree fertilization

1. Soil fertilization

Soil fertilization should be applied below the soil surface, which is beneficial to root absorption and can also reduce fertilizer loss. Some chemical fertilizers are volatile; if not buried in the soil, the loss is great. For example, if ammonium bicarbonate is spread on the surface, the drier the soil, the greater the loss. In an ammonium sulfate experiment, when applied 1 cm, 2 cm, and 3 cm below the soil surface, the reductions in loss compared with application on the soil surface were 36%, 52%, and 60%, respectively. Soil fertilization can use the following methods:

Ring (wheel-shaped) fertilization: According to the size of the tree canopy, dig a ring-shaped ditch centered on the trunk, with the radius being the tree's drip line (the drip line refers to the line where the canopy extends vertically down to the ground). The depth of the ditch depends on the depth of root distribution, generally 20-30 cm deep and 30 cm wide. Then put in fertilizer and bury it back with soil. This situation is usually used when there is relatively little fertilizer or for young trees.

Radial ditch (radiating) fertilization: Open ditches outward from under the canopy, with the inner end starting slightly inside the projection of the outer edge of the canopy and the outer end extending beyond the projection of the outer edge of the canopy. The number of ditches is 4 to 8, and the width and depth depend on the amount of fertilizer. After fertilization, cover with soil. This fertilization method damages fewer roots, can promote root absorption, and is suitable for mature trees; trees planted too densely are also not suitable for it. When fertilizing the next year, the ditch positions should be staggered.

Whole-orchard fertilization: First spread the fertilizer over the entire orchard, then mix it with the soil using a harrow or turn it into the soil. Under sod conditions, it is enough to spread the fertilizer on the grass. Whole-orchard fertilization followed by irrigation is highly efficient. This method has a large fertilization area and is beneficial to root absorption; it is suitable for mature trees and densely planted trees.

Strip ditch fertilization method: With the tree trunk as the center, draw two parallel lines on each of the left and right sides of the tree. The distance from the lines to the tree trunk is the distance from the drip line to the tree trunk, with a depth and width of 30 cm each. After fertilization, cover and level with soil. This is usually used on mature trees.

Basin-shaped ditch fertilization method: With the tree trunk as the center, dig 6 to 4 pits 30 cm wide on the circle with the drip line as the radius, then evenly spread fertilizer into the basin, and then cover and level with soil. It is often used for fertilizing young trees.

Broadcast fertilization method: Evenly spread fertilizer around the tree, then combine with deep raking in late autumn and early winter or early spring to turn the fertilizer into the soil. It is suitable for mature trees whose root systems have already covered the entire orchard, but it cannot be used for a long time.

2. Fertilization outside the roots

This includes branch and trunk smearing or spraying, branch and trunk injection, and foliar spraying. In production, foliar spraying is the most commonly used method.

Branch and trunk smearing or spraying: Suitable for supplementing trace elements such as iron and zinc to trees. It can be done together with winter trunk whitening. The method is to add ferrous sulfate or zinc sulfate to white lime slurry, and the concentration can be higher than that for foliar spraying. Tree bark can absorb nutrient elements, but the efficiency is not high; after rain, the fertilizer on the trunk gradually seeps somewhat into the bark, or is washed into the soil under the canopy and then absorbed somewhat by the roots.

Branch and trunk injection: A high-pressure sprayer plus a modified injector can be used. First drill a hole in the trunk, then inject forcefully into the trunk with the injector. It is used to inject ferrous sulfate (1%-4%) and chelated iron (0.05%-0.10%) to control iron deficiency, and adding boric acid and zinc sulfate also has an effect. All nutrient deficiencies are related to soil conditions. When relying on soil fertilization has poor results, trunk injection has a good effect.

3. Fertigation

Fertigation is a method of fertilizing trees by applying fertilizer through an irrigation system (sprinkler irrigation, micro-irrigation, drip irrigation).

II. Field crop fertilization

1. Broadcast application: This is the even spreading of fertilizer into the soil. Broadcast application can be deep or surface (shallow). The technique of deep application is to spread it and then plow it into the lower soil layer; for surface application, it is enough to harrow it over. Broadcast application is suitable for densely planted crops and situations with a relatively large fertilization amount. The advantages of broadcast application are that it is simple and convenient, and nutrients are available in all parts of the soil for crop absorption; the disadvantages are that the fertilizer utilization rate is not high, because the fertilizer cannot all be used by the crops, and at the same time it fertilizes weeds. Water-soluble phosphate fertilizer has too much contact with the soil and is easily fixed, reducing fertilizer efficiency, and the fertilizer dosage is large.

2. Band application and hole application: Applying fertilizer in seeding furrows and seeding holes, or in transplanting rows and holes, is called band application and hole application. Fertilizer can be applied below the seeds, or on one side or both sides of the seeds.

The following situations are suitable for band application and hole application:

① The fertilizer dosage is small;

② The crop spacing is large;

③ Fertilizers that are easily fixed by the soil, such as phosphate fertilizer;

④ The crop root system develops poorly, and the soil fertility is relatively low.

The advantages of this fertilization method are: the fertilizer is close to the roots and is easily absorbed and used by the crops, so the fertilizer utilization rate is relatively high; the contact surface between fertilizer and soil is small, the degree to which nutrient elements are fixed is low, and the effective time is longer than with broadcast application.

3. Mechanical fertilization, also called simultaneous sowing of seed and fertilizer.