A. Overview of Organic Fertilizer
Organic fertilizer is a carbon-containing material whose primary function is to provide plant nutrition. It is primarily derived from plants and/or animals, processed from biomass, animal and plant waste, and plant residues, and is rich in beneficial substances.
Organic fertilizer plays a vital role in agricultural production. First, it enhances soil fertility. Bio-organic fertilizer contains a large number of beneficial microorganisms that decompose organic matter in the soil, increase soil aggregate structure, and improve soil composition. The microscopic channels left behind by the dying microorganisms in the soil increase soil aeration and water and fertilizer storage capacity, preventing and eliminating soil compaction. Furthermore, the beneficial microorganisms in organic fertilizer can inhibit the growth of harmful pathogens, reduce pesticide use, save labor and money, and be pollution-free. Furthermore, while most trace elements in the soil exist in an insoluble form, the organic acids produced by microbial metabolites can dissolve these trace elements, converting them into nutrients that plants can directly absorb and utilize, significantly increasing the soil’s fertility capacity.
Organic fertilizers also have a long-lasting effect. The microorganisms within them survive in the soil for extended periods. Nitrogen-fixing, phosphate-solubilizing, and potassium-solubilizing bacteria utilize nitrogen from the air and release potassium and phosphorus in the soil that are difficult for crops to absorb, continuously supplying nutrients to crops. Data confirms that the utilization rate of chemical fertilizers is only 30% to 45%. However, when applied, the beneficial biological activity of organic fertilizers improves soil structure, reduces nutrient loss, and increases the effective utilization rate of chemical fertilizers to over 50%. Furthermore, organic fertilizers can increase crop yields and improve the quality of agricultural products. When used as base fertilizer or topdressing, they often outperform chemical fertilizers, especially in improving the quality of agricultural products.
In short, organic fertilizers play a vital role in enhancing soil fertility and increasing production and income.
B. Precautions for Use
a. Nutrients Are Not a Panacea
Although organic fertilizers contain a variety of nutrients, the content and ratio of these nutrients may not necessarily fully meet the requirements for high yield and quality. Different crops have different nutrient requirements at different growth stages, and organic fertilizers contain a wide variety of nutrients, but they are often unbalanced. For example, some crops may require large amounts of nitrogen in their early stages to promote stem and leaf growth, but organic fertilizers may contain relatively low nitrogen content and release it slowly. Furthermore, some crops with high requirements for specific trace elements may not be able to obtain sufficient amounts of these elements from organic fertilizers. Therefore, when using organic fertilizers, you cannot rely solely on them to provide all nutrients. You need to appropriately combine them with other fertilizers, such as chemical fertilizers, based on the crop’s needs to ensure a comprehensive and balanced nutritional profile.
b. Requires Fermentation
Raw manure should not be applied directly to the field for the following reasons. First, many organic fertilizers, especially unprocessed raw manure, contain pathogens, insect eggs, and weed seeds. If applied directly to the field, these pathogens may cause crop diseases, impacting growth and yield. For example, pathogens and pests such as E. coli and nematodes in raw manure can directly spread pests and diseases, causing crop disease and impacting the health of people who consume the agricultural products. Second, raw manure contains insect eggs, especially chicken manure, which is particularly prone to harboring root-knot nematodes. Research has shown that nematode eggs in raw chicken manure hatch easily, multiplying to tens of thousands overnight. Soil nematode incidence is highest in plots containing chicken manure. Furthermore, applying raw manure directly to the soil can easily burn seedlings and roots. This is because once the manure reaches a certain temperature, it undergoes secondary fermentation. If you insert your hand into the soil during this period, the soil will feel warmer. Fermented chicken manure releases a significant amount of heat, which can lead to root and seedling burns.
c. Slow Decomposition and Delayed Fertilizer Effect
Organic fertilizers decompose slowly and take effect slowly, a key characteristic of organic fertilizers. When used in small quantities, they can hardly meet the nutritional needs of crops. This is because the nutrients in unfermented manure are mostly in an organic or slow-release form, which cannot be directly absorbed and utilized by crops. They must decompose and convert to a fast-release form before they can be absorbed and utilized by crops. For example, for crops with short growth cycles, relying solely on organic fertilizers can lead to nutrient deficiencies during critical growth stages due to their slow release of nutrients, impacting growth and yield. Therefore, when using organic fertilizers, it’s important to consider their fertilizer release characteristics and, based on the crop’s growth needs, rationally arrange fertilization timing and methods. If necessary, combine with fast-acting fertilizers to meet the nutrient needs of crops at different growth stages.
d. Contraindications
Mature organic fertilizers should not be mixed with alkaline fertilizers or nitrate nitrogen fertilizers. Firstly, alkaline fertilizers should not be mixed with well-decomposed organic fertilizers. Highly mature organic fertilizers contain more fast-acting nutrients, most of which are in the form of ammonium nitrogen. Mixing them with alkaline fertilizers will cause ammonia volatilization, reducing the nutrient content of the organic fertilizer. Commonly used alkaline fertilizers include lime nitrogen and wood ash. Secondly, nitrate nitrogen fertilizers should not be mixed with organic fertilizers. Organic fertilizers contain a large amount of organic matter, which, when combined with nitrate nitrogen fertilizers, will undergo nitrification under the action of denitrifying bacteria, resulting in nitrogen loss. Commonly used nitrate nitrogen fertilizers include ammonium nitrate and calcium ammonium nitrate. Furthermore, nitrate nitrogen fertilizer should not be used in paddy fields or in rainy southern regions. It should also not be applied before or after heavy rain in dry areas, or after heavy watering to prevent nitrogen loss and reduced fertilizer efficiency.
C. Correct Usage
a. Proper Combination
Applying organic fertilizers in combination with chemical fertilizers can complement each other and improve fertilizer efficiency. Chemical fertilizers are high in nutrients and have a rapid effect, but their effects are short-lived; organic fertilizers provide comprehensive nutrients and a long-lasting effect, improving soil quality. Combining the two can prevent competition between microorganisms and crops for nitrogen. For example, the application of organic fertilizers improves soil structure and increases soil water and fertilizer retention capacity due to beneficial biological activity, thereby reducing nutrient loss and increasing the effective utilization rate of chemical fertilizers to over 50%. This also reduces chemical fertilizer usage and reduces fertilization costs.
b. Avoiding Concentrated Large-Scale Applications
Concentrated large-scale application of organic fertilizers may cause some harmful effects. On the one hand, low fertilizer utilization rates mean that applying large amounts of fertilizer can easily lead to a concentration of phosphorus and potassium, resulting in soil nutrient imbalance. On the other hand, in greenhouses where fertilizer mobility is limited, applying large amounts of fertilizer can also increase soil salt concentrations. The correct application method involves applying high-nutrient commercial organic fertilizers, in addition to large amounts of coarse organic fertilizers, within the planting hole or through trenching. This concentrates the fertilizer application on the root zone to maximize its effectiveness. Furthermore, depending on the quality of the organic fertilizer and the growth of the crop’s root system, fertilizer should be applied at a distance from the planting hole, allowing it to take effect as the crop’s roots grow.
c. Apply after it is fully decomposed
Undecomposed organic fertilizers can pose many risks. For example, it can easily cause root and seedling burn. When fermentation conditions are met, the heat generated by raw manure fermentation can affect crop growth, causing root and seedling burn, and in severe cases, plant death. Manure can also pose a threat to pests and diseases. Manure contains pathogens and pests such as E. coli and nematodes. Direct use can spread pests and diseases and cause crop disease. It also produces harmful gases. During decomposition, methane and ammonia are produced, which acidify the soil and damage the roots of fruit trees. The correct fermentation method involves collecting fresh livestock and poultry manure, controlling the moisture content to around 60%, and piling it together. It can also be mixed with crushed crop straw. Superphosphate should be added to each cubic meter of organic fertilizer, and the mixture should be evenly mixed. The mixture should then be piled together and covered with colorless, transparent plastic film. Allow the compost to ferment naturally until mature. After two weeks, turn the pile over and cover again to heat it up. When the manure begins to grow white hairs, it’s fermented and can be used directly in the field or sun-dried and stored.
d. Five Key Points for Scientific Application
For crop fertilization, human and livestock manure can be applied to most crops, but leafy vegetables, cereals, and fiber crops are most suitable. Manure contains high levels of chlorine, so it should not be applied to chlorine-sensitive crops such as sweet potatoes, tobacco, and potatoes.
Apply after composting. Most organic fertilizers often contain pathogens, insect eggs, and weed seeds. Uncomposted, they are detrimental to crop growth. Therefore, they should be composted and fermented before application. (Insecticides and fungicides such as phoxim can be added to organic fertilizers.)
Base application and deep application are essential. Organic fertilizers have a long-lasting effect and slowly release nutrients, so they should generally be applied as base fertilizer. Applying organic fertilizer during deep tillage promotes soil-fertilizer integration, promotes the formation of soil aggregates, and effectively improves soil properties.
Fertilizer dosage should be limited. Organic fertilizers are bulky and low in nutrients, requiring large amounts to meet crop growth needs. However, more is not always better. For example, when growing Chinese cabbage, 4,000 to 6,000 kg of well-rotted organic fertilizer per mu (approximately 1.5 to 2.5 acres) is sufficient.
Apply fertilizers appropriately. Sheep manure has the highest nutrient content among livestock manures, decomposes quickly, and produces a stronger fertilizer. To achieve a more balanced fertilizer, add pig or cow manure to the mix. Human manure is a fast-acting organic fertilizer and should be applied in combination with soil-based fertilizers and phosphorus and potassium fertilizers.
e. As a basal fertilizer, topdressing, seedling fertilizer, and nutrient soil application
Base fertilizer application can be done through-the-soil or in-the-soil applications, each with its own advantages and disadvantages. For full-thickness application, spread the organic fertilizer onto the surface during tillage, then work it into the soil as you till the soil, then incorporate it into the soil. This method of fertilization is simple, labor-saving, and provides even fertilizer application. However, it has a low fertilizer utilization rate and can easily create soil barriers. In greenhouses, where fertilizer mobility is limited, it can also increase soil salt concentrations. Focused application involves applying high-nutrient commercial organic fertilizers within the planting hole or through trenches, concentrating them on the root zone to maximize their effectiveness. However, the placement of fertilizers should be adjusted based on the quality of the organic fertilizer and the growth of the crop’s root system.
Topdressing with organic fertilizers should be done early. Organic fertilizers contain fast-acting nutrients, but their quantity is limited, and the release of large amounts of slow-release nutrients takes time. Therefore, topdressing with organic fertilizers should be applied several days earlier than with chemical fertilizers. Later topdressing should be supplemented with nutrients based on crop growth. If certain components are lacking in the organic fertilizer, an appropriate single chemical fertilizer can be applied to supplement them. A reasonable ratio of basal fertilizer to topdressing should also be established. When ground temperature is low, microbial activity is low, and nutrient release from organic fertilizers is slow. Therefore, the majority of the applied amount can be applied as basal fertilizer. When ground temperature is high, the amount of basal fertilizer applied should be reduced, and the amount of topdressing applied should be increased.
For seedling fertilizer, fully decomposed organic fertilizer releases nutrients evenly and comprehensively, making it an ideal fertilizer for seedling cultivation. Generally, 10% fully fermented organic fertilizer is added to a certain amount of peat, vermiculite, or perlite, and mixed evenly with soil to create a seedling medium.
Using this as nutrient soil reduces costs and provides a continuous nutrient supply. Organic fertilizer is added to the medium as a nutrient source for crop growth. Adding solid fertilizer to the medium at regular intervals throughout the crop’s growth period ensures a continuous nutrient supply. Using organic fertilizer instead of regular nutrient solution irrigation reduces the frequency of nutrient solution irrigation during cultivation, reducing production costs.
D. Methods for Improving Effectiveness
“Raw manure” is used after it has been fully composted to kill pathogens, insect eggs, and inactivate heavy metals. Fresh livestock and poultry manure is piled up and fermented. The high temperature of fermentation kills nematodes, pathogens, and insect eggs contained in the manure, and inactivates heavy metals, preventing soil damage.
As a base fertilizer, in combination with chemical fertilizers, bagged bio-organic fertilizers or returning straw to the field can be used. Organic fertilizer boasts a comprehensive nutrient profile, long-lasting effects, and slow nutrient release. It’s better used as a base fertilizer than a topdressing. Before planting crops, spread the organic fertilizer evenly on the surface, plow the soil, and then plant the crops. It can be applied in combination with chemical fertilizers. If livestock manure isn’t readily available as organic fertilizer, bagged bio-organic fertilizers can be used, though this is more expensive. Crop straw can be crushed and then mixed with an appropriate amount of urea to promote decomposition, thereby increasing its effectiveness.
Furrow application and broadcast application are available. Fertilize fruit trees through trenches, and spread fertilizer around the roots of overwintering crops to improve their cold resistance. For fruit trees, create radial fertilizer trenches around the base of the trees in late autumn each year. These trenches are generally about 40 cm deep and 30 cm wide. Fill the trenches with organic fertilizer, cover with soil, and water gently to keep the soil moist for optimal nutrient utilization. For overwintering crops, spreading organic fertilizer around the root base can improve their cold resistance. Furthermore, with the added benefit of rain and snow in winter and spring, the organic fertilizer will be even more effectively utilized.
As an important fertilizer resource, organic fertilizer plays an irreplaceable role in agricultural production. Proper use of organic fertilizer not only improves soil fertility, improves soil structure, and promotes crop growth, but also reduces the use of chemical fertilizers, lowers agricultural production costs, and protects the ecological environment.
When using organic fertilizer, we must pay attention to the following points: First, we must recognize that organic fertilizer’s nutrients are not a panacea and must be appropriately combined with other fertilizers, such as chemical fertilizers, based on crop needs. Second, raw manure should not be applied directly to the field; it must be fermented to kill pathogens, insect eggs, and weed seeds to avoid seedling burn. Third, we must understand the slow decomposition and delayed effectiveness of organic fertilizers and plan the application time and method appropriately. Fourth, we must observe the contraindications for using organic fertilizers and avoid mixing them with alkaline fertilizers and nitrate nitrogen fertilizers.
Also, we must master the correct use of organic fertilizers. Properly combine organic and chemical fertilizers to leverage their strengths and offset their weaknesses, improving fertilizer efficiency. Avoid concentrating large amounts of organic fertilizer; select appropriate locations for application based on the root growth of crops. Apply organic fertilizer after it is fully decomposed to reduce the occurrence of pests and diseases and their harm to crops. Apply organic fertilizer scientifically, applying it according to the crop, applying it after it is fully decomposed, prioritizing basal application and deep application, controlling the amount of fertilizer applied, and mixing it rationally. Use organic fertilizer as basal fertilizer, topdressing, seedling fertilizer, and nutrient soil to maximize its diverse benefits. Improve the effectiveness of organic fertilizer by using “raw manure” after it is fully decomposed, applying it as a base fertilizer, applying it through trenches, and broadcasting it.
In short, only by correctly understanding and mastering the application methods and precautions of organic fertilizer can we better maximize its benefits and contribute to agricultural harvests and ecological environmental protection. Let us actively promote the proper use of organic fertilizer and promote sustainable agricultural development.
