In short, organic fertilizer refers to organic materials such as animal and plant residues, excrement, or biowaste, produced through microbial action or natural fermentation. It contains a high amount of organic matter and provides comprehensive plant nutrition.
A. Definition and Classification of Organic Fertilizers
Unlike chemically synthesized inorganic fertilizers, organic fertilizers focus more on restoring and maintaining the soil’s ecological balance, promoting soil microbial activity, and improving the soil’s ability to retain water and fertilizer. Based on the source of the raw materials, organic fertilizers can be divided into the following categories:
Animal-derived organic fertilizers: These primarily include livestock and poultry manure (such as cow dung, pig manure, and chicken manure), fish meal, and bone meal. These fertilizers are rich in macronutrients such as nitrogen, phosphorus, and potassium, as well as various trace elements and growth hormones, and are extremely beneficial to crop growth.
Plant-derived organic fertilizers: These include crop straw, green manure, fallen leaves, and sawdust. These materials, through composting, can be converted into humus-rich organic fertilizers, increasing soil organic matter content and improving soil structure.
Microbial fertilizers, including bacterial fertilizers and bio-organic fertilizers, use specific microorganisms to convert organic matter into a form that crops can directly absorb and utilize, while also enhancing crop resistance and quality.
Mixed organic fertilizers: These fertilizers are made by mixing several of the aforementioned raw materials in a specific ratio. They aim to combine the advantages of each fertilizer type to provide a more comprehensive nutritional support.
B. Choosing the Right Organic Fertilizer
There are many types of organic fertilizers, including animal manure (such as cow and sheep manure), plant residues (such as straw and green manure), compost, and cake fertilizer. Different types of organic fertilizers vary in their nutrient content, release rate, and suitable crops.
Choosing the right organic fertilizer requires a comprehensive consideration of crop needs, soil conditions, and climatic conditions. For example, for acidic soils, an appropriate amount of lime-based organic fertilizer (such as wood ash) can be added to neutralize the acidity. For nitrogen-loving crops such as leafy vegetables, soybean cake fertilizer with a high nitrogen content or thoroughly decomposed animal manure can be used. For orchards or vegetable gardens that need to improve soil structure, compost is an ideal choice, as it increases soil organic matter content and improves soil aggregate structure. Furthermore, ensure that the organic fertilizer comes from a reliable source and avoid using fertilizers containing heavy metals or other harmful substances.
C. Master the Timing of Application
The timing of applying organic fertilizer is crucial. Generally, basal fertilizer should be applied before planting crops or before sowing or transplanting. During this time, soil temperatures are lower, allowing the fertilizer’s organic matter to fully decompose and provide continuous nutritional support for crop growth.
Topdressing should be flexibly scheduled based on the crop’s growth cycle and nutrient needs. For example, topdressing should be applied during peak or critical growth periods to meet the needs of rapid growth. For crops with long growing seasons, such as fruit trees and forest trees, topdressing with organic fertilizer can also be applied at appropriate times during the growing season.
In addition, spring and autumn are excellent times for soil improvement and fertilization. Applying organic fertilizers during this time can effectively improve the soil environment and lay a good foundation for crop growth next year. Applying organic fertilizers in winter can also help raise soil temperatures and protect crop roots from frost damage.
D. Scientific Application Methods
Deep Application and Mulching: For solid organic fertilizers, such as compost and cake fertilizer, deep application and mulching are recommended. This involves applying the fertilizer deep into the soil and then covering the soil to reduce nutrient loss and improve fertilizer utilization.
Mulching: Crop residues such as straw and green manure can be directly turned over and returned to the field, where they are covered directly on the surface. They will then naturally decompose and convert into soil organic matter. This method is both environmentally friendly and economical, but care should be taken to control the thickness of the mulch to avoid affecting crop growth.
Furrow or Hole Application: For high-value crops such as fruit trees and vegetables, deep application methods such as furrow or hole application can be used to apply fertilizer directly into the root zone to promote root absorption.
Tilling after spreading: Before planting, organic fertilizer can be evenly spread on the surface. Tilling is then used to mix the fertilizer into the soil and evenly distribute it throughout the tillage layer, avoiding areas where it is too concentrated or too diluted.
Liquid organic fertilizer: Liquid organic fertilizers, such as biogas slurry and humic acid, can be applied through irrigation systems or foliar sprays to quickly replenish crop nutrients.
Combined irrigation: In arid areas or when soil moisture is insufficient, organic fertilizer can be dissolved in water and applied through drip irrigation or sprinkler irrigation. This not only replenishes soil moisture but also promotes fertilizer dissolution and absorption.
E. Precautions
When applying organic fertilizer, soil conditions, crop needs, and local resource availability should be comprehensively considered. For example, while livestock and poultry manure is rich in nitrogen, phosphorus, potassium, and trace elements, it may contain heavy metals and pathogens, so it must be treated before use. Crop straw and green manure are more suitable for improving soil structure and increasing soil organic matter content. Here are some common precautions:
Avoid overapplication: While organic fertilizers are beneficial to soil and crops, excessive application can lead to nutrient overload, hindering crop growth and even causing environmental pollution. Therefore, the application rate should be appropriately determined based on soil test results and crop needs.
Fully decomposed: Undecomposed organic fertilizers may contain harmful substances such as pathogens and insect eggs, which can harm crop health if applied directly. Therefore, ensure that the fertilizer is fully decomposed before use.
Combined application: Organic fertilizers and chemical fertilizers each have their own advantages and disadvantages. Proper combination can complement each other and improve fertilization effectiveness. For example, organic fertilizers can be added to base fertilizers and topdressed with an appropriate amount of fertilizer based on crop growth.
Combining fertilization with irrigation: Irrigate promptly after fertilization to promote fertilizer dissolution and root absorption. However, avoid heavy flooding to prevent nutrient loss.
F. Effectiveness Evaluation and Adjustment
After applying organic fertilizers, regularly observe crop growth and evaluate the fertilizer’s effectiveness. By observing indicators such as crop leaf color, growth rate, yield, and quality, we can initially assess the effectiveness of fertilizer application. Furthermore, combined with soil testing results, we can analyze soil nutrient changes and provide a basis for the next round of fertilization. If fertilization results are unsatisfactory, we should promptly adjust the fertilization plan, such as increasing the amount of fertilizer applied, changing the fertilization method, or selecting a more suitable fertilizer type.
In short, the effectiveness of organic fertilizers is influenced by many factors, including fertilizer type, application timing, application method, and soil and climatic conditions. The scientific and rational application of organic fertilizers not only increases crop yield and quality, but also improves the soil environment and promotes sustainable agricultural development. Therefore, mastering the techniques for efficient utilization of organic fertilizers is of great significance to modern agricultural production.
