How to Choose Compound Fertilizer in Autumn? Master These Tips for a Bountiful Harvest​

Autumn is a critical period in agricultural production. It is not only the season for ripening and harvesting various crops, but also a key stage for sowing and raising seedlings of overwintering crops such as wheat and rapeseed, as well as nutrient accumulation in fruit trees and vegetables. Choosing compound fertilizer reasonably at this time can not only provide sufficient nutrients for crops to promote their growth and development, but also enhance their cold resistance and stress tolerance, laying a solid foundation for high yields in the following year. However, facing a wide variety of compound fertilizers on the market, many farmers often do not know where to start. In fact, the core of selecting the right compound fertilizer for autumn lies in accurately controlling the content ratio of the three major nutrient elements (nitrogen, phosphorus, and potassium) based on the crop type and growth stage. Below is a detailed introduction to the key points for selecting compound fertilizer for autumn application.​

Clarify the Common Nutrient Requirements of Autumn Crops and Grasp the Core Direction of Fertilizer Selection​

In autumn, the climate gradually cools down, and the temperature difference between day and night increases. The growth rhythm of crops changes significantly compared with summer, and their nutrient requirements also show unique commonalities. On one hand, most crops enter the nutrient accumulation stage in autumn, requiring sufficient nutrients to promote fruit development, plump seeds, or store energy for overwintering. On the other hand, as the temperature decreases, the absorption capacity of crop roots will weaken, requiring higher fertilizer utilization efficiency. Therefore, compound fertilizer should not only have balanced nutrients but also good solubility and absorbability.​

From the perspective of nutrient element requirements, autumn crops have different focuses on nitrogen (N), phosphorus (P), and potassium (K), but generally follow the basic principle of "controlling nitrogen, stabilizing phosphorus, and increasing potassium". "Controlling nitrogen" is because excessive nitrogen application in autumn can easily lead to excessive vegetative growth of crops, thinner cell walls, and reduced cold resistance. Especially for overwintering crops, this may increase the risk of frost damage. "Stabilizing phosphorus" is due to the fact that phosphorus can promote the growth of crop roots, enhance their ability to absorb nutrients and water, and at the same time promote crop flowering, fruiting, and seed ripening, which is crucial for the growth of autumn crops. "Increasing potassium" is because potassium can improve the stress resistance of crops, including cold resistance, drought resistance, and disease and pest resistance. It can also promote the transportation and accumulation of photosynthetic products, improving crop quality and yield, which is very important for coping with the changeable autumn climate.​

Select Compound Fertilizer According to Crop Type to Accurately Match Nutrient Requirements​

Overwintering Grain Crops: Wheat, Barley​

After sowing in autumn, wheat goes through three stages: seedling emergence, tillering, and overwintering. The selection of compound fertilizer at this time should take into account both root promotion and seedling strengthening. It is recommended to choose compound fertilizer with a nitrogen-phosphorus-potassium content ratio of 15-20-10 or 16-18-8. This type of compound fertilizer has a relatively high phosphorus content, which can promote the development of wheat roots, enhance tillering ability, and lay a foundation for safe overwintering. At the same time, an appropriate amount of nitrogen can promote the growth of seedlings and avoid weak seedlings. Potassium can improve the cold resistance of wheat and reduce the occurrence of frost damage.​

When using, compound fertilizer can be applied as base fertilizer, with an application rate of about 30-40 kg per mu. It should be ploughed into the deep soil and fully mixed with the soil to facilitate root absorption. If the soil fertility is poor, a small amount of nitrogen fertilizer can be top-dressed at the three-leaf stage of wheat, but attention should be paid to controlling the dosage to avoid excessive vegetative growth.​

Cash Crops: Rapeseed, Garlic​

① Rapeseed​

After sowing in autumn, rapeseed needs to quickly establish a vegetative body to prepare for flowering and pod formation in the following spring. It has a relatively balanced demand for nitrogen, phosphorus, and potassium, and is sensitive to boron (although the boron content in compound fertilizer is low, attention should be paid to supplementary application later). It is recommended to choose compound fertilizer with a nitrogen-phosphorus-potassium content ratio of 14-16-10 or 15-15-10. This type of compound fertilizer can meet the nitrogen, phosphorus, and potassium requirements of rapeseed at the seedling stage, promoting leaf growth and root development.​

The base fertilizer application rate of compound fertilizer for rapeseed is 35-45 kg per mu. If the soil is deficient in boron, 0.5-1 kg of boron fertilizer (such as borax) can be applied together. Before rapeseed overwinters, according to the seedling condition, a "winter fertilizer" can be top-dressed, mainly organic fertilizer, combined with a small amount of compound fertilizer to enhance cold resistance.​

② Garlic​

After planting in autumn, garlic goes through the stages of germination and seedling growth. Its roots are fibrous roots with weak absorption capacity, so it has high requirements for fertilizers, especially requiring sufficient phosphorus and potassium to promote bulb development. It is recommended to choose high-phosphorus and high-potassium compound fertilizer with a nitrogen-phosphorus-potassium content ratio of 12-18-15 or 10-20-15. This type of compound fertilizer can promote the growth of garlic roots, enhance stress resistance, and accumulate nutrients for bulb expansion in the later stage.​

The base fertilizer application rate of compound fertilizer for garlic is 40-50 kg per mu. It should be evenly spread and ploughed into the soil during soil preparation. After garlic emerges, a "seedling-promoting fertilizer" mainly composed of nitrogen fertilizer can be top-dressed to promote seedling growth. When entering the bulb expansion stage, another application of high-potassium fertilizer can be carried out to further improve yield.​

Fruit Trees: Apple, Pear, Citrus, Etc.​

Autumn is a critical period for nutrient accumulation in fruit trees. After fruit harvesting, the tree consumes a large amount of nutrients and needs to be supplemented in a timely manner to restore tree vigor and reserve nutrients for flower bud differentiation and fruiting in the following year. The autumn fertilization of fruit trees should focus on "root nourishment and phosphorus-potassium supplementation". It is recommended to choose high-potassium compound fertilizer with a nitrogen-phosphorus-potassium content ratio of 10-15-20 or 8-12-25. This type of compound fertilizer has a relatively high potassium content, which can promote the accumulation of photosynthetic products in fruit trees and enhance their cold resistance. At the same time, an appropriate amount of phosphorus can promote root growth and flower bud differentiation, reducing the phenomenon of alternate bearing (yearly fluctuation in yield).​

When applying compound fertilizer to fruit trees, the circular furrow application or strip furrow application method can be adopted. A furrow with a depth of 20-30 cm should be dug near the drip line of the tree crown. The application rate per mu depends on the tree age and tree vigor. Generally, each mature fruit tree requires 1-1.5 kg, and each young tree requires 0.5-0.8 kg. Water should be applied in a timely manner after fertilization to promote fertilizer dissolution and absorption.​

Autumn Vegetables: Chinese Cabbage, Radish, Cabbage, Etc.​

Autumn vegetables have a short growth cycle and concentrated nutrient requirements. They need to quickly supplement nitrogen, phosphorus, and potassium to promote leaf growth or the development of taproots and tubers. For example, leafy vegetables such as Chinese cabbage and cabbage have a high demand for nitrogen, but also require an appropriate amount of phosphorus and potassium to enhance disease resistance. Root vegetables such as radish and carrot need sufficient potassium to promote taproot expansion.​

For leafy vegetables, it is recommended to choose compound fertilizer with a nitrogen-phosphorus-potassium content ratio of 18-10-12 or 20-8-10. The base fertilizer application rate is 30-40 kg per mu. During the growth period, nitrogen fertilizer can be top-dressed 1-2 times to promote leaf growth. For root vegetables, it is recommended to choose compound fertilizer with a nitrogen-phosphorus-potassium content ratio of 15-10-18 or 16-8-20. The base fertilizer application rate is 35-45 kg per mu. During the taproot expansion stage, high-potassium fertilizer can be top-dressed to improve yield and quality.​

Pay Attention to Compound Fertilizer Quality and Application Details to Improve Fertilizer Efficiency​

In addition to selecting compound fertilizer with the appropriate nitrogen-phosphorus-potassium content according to crop type, attention should also be paid to the quality of compound fertilizer and application details to give full play to the role of fertilizers, avoid resource waste and environmental pollution.​

(1) Identify the Quality of Compound Fertilizer​

High-quality compound fertilizer has uniform particles, consistent color, no obvious caking, and is not easy to break when rubbed by hand. At the same time, attention should be paid to checking the nutrient content label of the fertilizer to ensure that the nitrogen, phosphorus, and potassium contents meet the label, avoiding the purchase of "substandard" fertilizers with lower actual nutrient contents than labeled.​

(2) Scientific Application of Compound Fertilizer​

Control the Dosage: Determine the dosage of compound fertilizer according to soil fertility and crop nutrient requirements. Avoid excessive application, which may lead to soil salinization, crop root burn, and other problems. For example, in plots with high soil fertility, the dosage of compound fertilizer can be appropriately reduced; for fertilizer-loving crops, the dosage can be appropriately increased, but the principle of "small amount and multiple times" should be followed.​

Reasonable Fertilization Methods: Compound fertilizer can be applied as base fertilizer or top-dressing. Base fertilizer is recommended to be applied to the deep soil in combination with deep ploughing, which is conducive to root absorption. Top-dressing can be carried out by hole application, strip application, or fertigation. For hole application and strip application, attention should be paid to keeping a certain distance (usually 10-15 cm) from the crop roots to avoid root burn. For fertigation, compound fertilizer should be fully dissolved to avoid nozzle blockage by particles.​

Combine with Other Fertilizers: Although compound fertilizer has comprehensive nutrients, it still needs to be used in combination with other fertilizers according to crop requirements. For example, when planting leguminous crops, rhizobium fertilizer can be used together to improve nitrogen fixation capacity; when planting leafy vegetables, foliar fertilizers (such as potassium dihydrogen phosphate solution) can be used together to promote leaf growth; when the soil is deficient in trace elements, trace element fertilizers (such as zinc fertilizer and iron fertilizer) should be supplemented in a timely manner.​