Choosing the right fertilizer for crop cultivation is crucial. Improper fertilizer selection can cause fertilizer damage to crops. With so many types of fertilizers available on the market, including organic, inorganic, and microbial fertilizers, which one should we choose?
Organic fertilizer refers to farmyard manure, which includes various plant and animal residues or metabolites, such as human excrement and straw, as well as cake fertilizer. These fertilizers undergo a series of processing steps to eliminate harmful substances and reach harmless standards. They effectively improve the physical and chemical properties of the soil.
Classification of Organic Fertilizers
Organic fertilizers can be categorized as agricultural waste, livestock manure, industrial waste, domestic waste, municipal sludge, and modern fertilizers.
Functions of Organic Fertilizers
First, organic fertilizers improve soil fertility, creating favorable soil conditions for plant growth.
Second, organic fertilizers can increase crop yields and enhance the quality of agricultural products.
Third, organic fertilizers can increase fertilizer utilization.
Precautions for Using Organic Fertilizer
First, bio-organic fertilizer should not be applied too deeply into the soil, as this will affect its activity.
Second, bio-organic fertilizer is best applied alone.
Third, applying bio-organic fertilizer in holes allows seedlings to absorb nutrients faster, invigorates the soil, and promotes rapid root growth and development.
Organic fertilizer is primarily derived from animal and plant waste, produced through biological fermentation, eliminating toxic and harmful substances. The Ministry of Agriculture standard is NY525-2012. Organic matter should be ≥45%, and nitrogen, phosphorus, and potassium should be no less than 5%. These are the key indicators!
The main functions of organic fertilizer are to improve soil fertility, increase yields, enhance product quality, improve fertilizer utilization, and promote the efficient absorption of chemical fertilizers.
- Inorganic Fertilizer
Inorganic fertilizer is a mineral fertilizer, also known as chemical fertilizer. It is characterized by simple ingredients, high levels of active ingredients, easy solubility in water, rapid decomposition, and easy root absorption, hence the name “fast-acting fertilizer.” Common chemical fertilizers are “inorganic fertilizers”. Inorganic fertilizers refer to fertilizers produced by chemical synthesis methods, including nitrogen, phosphorus, potassium, and compound fertilizers.
Classification of inorganic fertilizers
(1) Ammonium bicarbonate: also known as ammonium bicarbonate, contains about 17% nitrogen. Under high temperature or humid conditions, it is very easy to decompose and produce ammonia volatilization. It has a weak acid reaction and is a fast-acting fertilizer.
(2) Urea: Contains 46% nitrogen and is the type of solid nitrogen fertilizer with the highest nitrogen content. The fertilizer effect is slower than ammonium sulfate, but the fertilizer effect is longer. Urea has a neutral reaction and is suitable for various soils. Generally, when used as foliar topdressing, its concentration is preferably 0.1%~0.3%.
(3) Ammonium sulfate: Contains 20%~21% nitrogen. The fertilizer effect of each kilogram of ammonium sulfate is equivalent to 60~100kg of human feces and urine. It is easily soluble in water, has a fast fertilizer effect, and a short effective period of generally 10~20 days. It has a weak acid reaction and is often used as topdressing.
(4) Calcium magnesium phosphate fertilizer: contains 14% to 18% phosphorus, is slightly alkaline, has a slow fertilizer effect, and a long after-effect. If composted with crop straw, garbage, manure, etc., it can produce organic acids during the fermentation process to increase fertilizer efficiency, and is suitable for use as a base fertilizer. It is suitable for acidic or slightly acidic soils and can supplement the lack of calcium and magnesium trace elements in the soil.
(5) Potassium sulfate: contains 48% to 52% potassium. It is mainly used as a base fertilizer, and can also be used as a topdressing fertilizer. It is suitable to dig a trench and apply it deep, close to the root layer for faster results. When used as a foliar topdressing fertilizer, the concentration should not exceed 0.1%. It has a neutral reaction, is not easy to absorb moisture and clump, and can be applied to general soil. Grapes are fruit trees that like potassium fertilizers, and the application of potassium sulfate is very effective.
(6) Wood ash: It is the residue left after the burning of plant bodies. Wood ash contains about 5% to 10% potassium, 1% to 4% phosphorus, 0.14% nitrogen, and about 30% calcium. Most of the potassium in wood ash is water-soluble and is a quick-acting fertilizer. It can be used as a topdressing fertilizer or a base fertilizer. Wood ash should not be mixed with ammonium sulfate, human feces, etc. to avoid nitrogen loss. It should be kept away from moisture during storage to prevent nutrient loss.
(7) Lime: It is alkaline and is a commonly used fertilizer in acidic soils in southern my country. After application, it not only increases the calcium content in the soil and improves the soil structure, but also neutralizes the acidity of the soil. When composting, mixing a small amount of lime can accelerate the decomposition.
- Biofertilizer/Microbial Fertilizer
As the name suggests, biofertilizer is a combination of bacteria and fertilizer. Bacteria refer to various beneficial microorganisms, and fertilizer can be organic fertilizer or inorganic fertilizers such as nitrogen, phosphorus, potassium, and trace elements. The main advantage of biofertilizer lies in its functional beneficial bacteria!
Soil Improvement
The beneficial microorganisms in microbial fertilizers produce carbohydrates, which account for 0.1% of soil organic matter. Combined with plant mucilage, mineral embryos, and organic colloids, they improve soil aggregate structure, enhance soil physical properties, and reduce soil particle loss. Under certain conditions, they can also participate in humus formation. Therefore, applying microbial fertilizers can improve soil physical properties and contribute to soil fertility.
Six Major Benefits of Microbial Fertilizers
a. Improving Soil Fertility
This is one of the main benefits of microbial fertilizers. For example, various autotrophic, associative, or symbiotic nitrogen-fixing microbial fertilizers can increase nitrogen content in the soil. The application of various phosphate- and potassium-dissolving microorganisms, such as Bacillus and Pseudomonas, can decompose insoluble phosphorus and potassium in the soil into phosphorus and potassium compounds that can be absorbed and utilized by crops, thereby increasing the supply of nutrients in the crop growth environment. The application of some microbial fertilizers increases soil organic matter and improves soil fertility.
b. Improving Soil Structure
Microorganisms can also secrete and produce large quantities of extracellular polysaccharides, such as capsular polysaccharides and peptidoglycans. Research shows that the sugars produced by these beneficial microorganisms account for 0.1% of soil organic matter. These sugars interact with plant root secretions and soil colloids to form soil aggregates. Furthermore, they participate in the formation of humus, improving soil physical and chemical properties.
c. Stimulating Crop Growth and Development
The microorganisms in some microbial fertilizers can also secrete plant hormones and vitamins to stimulate and regulate crop growth and development. For example, nitrogen-fixing bacteria can produce a variety of active substances (auxins, cyclohexanehexol, pantothenic acid, pyridoxine, thiamine, etc.). Indole-3-acetic acid can be detected in nitrogen-fixing bacteria cultures. All strains of Pseudomonas fluorescens can produce gibberellins and gibberellin-like substances, some strains also produce indoleacetic acid, and a few strains can synthesize biotin and pantothenic acid. Arbuscular mycorrhizal fungi can induce forage plants to produce cytokinins (CTKs), altering the ratio of abscisic acid (ABA) to gibberellins.
d. Improving Crop Quality
Many microbial fertilizers can improve crop quality. Nitrogen fixed by rhizobia can be transported to grains, increasing the protein content of legumes. Furthermore, application of certain microbial fertilizers can increase the vitamin content of some vegetables, reduce nitrate levels in leafy vegetables, and increase sugar content in fruiting vegetables.
e. Enhancing Plant Disease (Pest) and Stress Resistance
The microorganisms in some microbial fertilizers can produce antibiotics, which can have a direct antagonistic effect on pathogens. Inhibit their growth and reproduction. Actinomycetes slender can secrete the antibiotic “5406,” which has a certain preventive effect on cotton diseases such as Verticillium wilt and Fusarium wilt. Furthermore, after beneficial microorganisms colonize crop roots, they grow and reproduce in large numbers, forming a dominant bacterial community in the crop rhizosphere. By occupying nutrient resources and living space, they gain a competitive advantage over pathogenic microorganisms, thereby inhibiting their growth and reproduction, and indirectly enhancing the plant’s disease resistance.
f. Reduce Fertilizer Use and Improve Fertilizer Utilization Efficiency
The use of microbial fertilizers can reduce the amount of chemical fertilizers used. Because microbial fertilizers increase soil nutrient content, they can reduce the amount of chemical fertilizers used on soils of the same soil quality while achieving equivalent yield increases. Microbial fertilizers play a significant role in improving fertilizer utilization efficiency. The appropriate combination of microbial fertilizers with chemical fertilizers, tailored to crop type, soil type, and climatic conditions, can increase crop yields while improving fertilizer utilization efficiency. This is not only economically beneficial, but also ecologically and environmentally.
In addition to the aforementioned benefits, microbial fertilizers also have the following advantages:
Application does not cause the accumulation of harmful substances in crops; they have no adverse effects on the agricultural ecological environment. Some microbial fertilizers also function as soil purifiers, reducing the accumulation of excessive organic matter in the soil. For example, microbial fertilizers that decompose cellulose and lignin can rapidly ferment municipal solid waste and agricultural and animal husbandry organic waste.
The basis for the effectiveness of microbial fertilizers is living microorganisms that perform specific functions. These microorganisms, through their growth, reproduction, and physiological activities, directly or indirectly influence plant physiological metabolism or soil environmental conditions. To fully maximize their effectiveness, microbial fertilizers must possess the following five key characteristics.
a. High Efficiency of the Bacterial Strains
High Efficiency of the Bacterial Strains: Microorganisms are the core of microbial fertilizers. These strains are selected and modified through artificial screening or bioengineering techniques for different crops and soil types, and then subjected to extensive scientific testing to obtain superior strains. Due to differences in the physiological and biochemical functions of the core strains or strains, the efficacy of different microbial fertilizers varies. For example, the nitrogen fixation capacity of rhizobia varies greatly, with some strains even lacking nitrogen fixation.
b. Abundant Active Microbial Quantity
The number of active microorganisms is the foundation for the full effectiveness of fertilizers. Any microbial fertilizer must contain a sufficient number of active, specific microorganisms. The quantity and purity of these specific microorganisms directly impact the effectiveness of microbial fertilizers and are important indicators of their quality. When the quantity of specific microorganisms in a microbial fertilizer drops below a certain level or the purity does not meet the required level, the fertilizer’s effectiveness will be reduced or even ineffective. Because the microorganisms have a limited lifespan, the shelf life of a microbial fertilizer is also a crucial factor in evaluating its quality.
c. Clear Type and Clear Function
The microorganisms that contribute to microbial fertilizers must be rigorously identified, have a clear taxonomic status, and be harmless to humans, animals, and plants, and will not disrupt the soil microecological environment. For example, while some Pseudomonas bacteria produce substances that promote plant growth during their growth and metabolism, they also produce certain harmful substances, some of which are even pathogens to humans, animals, or plants. Therefore, these microorganisms cannot be used as microbial fertilizers. Historically, there have been lessons learned from the use of unidentified microorganisms that have caused harm. “Effectiveness and harmlessness” are the principles for the production and application of microbial fertilizers, and many countries have clear legislation on this principle.
d. Highly targeted and suitable for a wide range of applications
Different microbial fertilizers are suitable for specific crops and soil conditions. In practice, many users fail to pay sufficient attention to this, leading to cases in my country where soybean rhizobium agents were mistakenly applied to wheat and corn.
e. Strict storage and application techniques
Environmental factors such as temperature, light, pH, and osmotic pressure can affect microbial survival. Microbial fertilizers should be stored in a dark, low-temperature environment. When applying microbial fertilizers, avoid prolonged exposure to sunlight to prevent ultraviolet rays from killing the microorganisms in the fertilizer. Microbial fertilizers should not be mixed directly with chemical fertilizers to prevent changes in osmotic pressure from inhibiting or killing the active bacteria.
So what are the advantages and disadvantages of these three types of fertilizers?
Inorganic fertilizers
Advantages: Inorganic fertilizers are mineral fertilizers, also known as chemical fertilizers. They are characterized by simple ingredients, high levels of active ingredients, easy solubility in water, rapid decomposition, and easy absorption by roots, hence the name “fast-acting fertilizer.”
Disadvantages: Inorganic fertilizers are chemical fertilizers, consisting of high-purity inorganic salts buried in the soil. These salts dissolve into the soil and are absorbed by plants. Due to the high concentration of inorganic salts, they can easily disrupt the soil’s acid-base balance, potentially harming the environment.
Advantages: The vitamins, humic acid, fulvic acid, palmitic acid, and low-molecular-weight organic acids, such as butyric acid, in organic fertilizers not only directly affect plant nutrition but also have physiologically active and stimulating effects, enhancing respiration and promoting root growth, directly impacting the soil’s environmental conditions.
Disadvantages: Organic fertilizers can also have low nutrient content and are difficult to decompose, making them inefficient for meeting crop yield requirements. Traditional organic fertilizers are also inconvenient to prepare and use. Organic waste, such as human and livestock manure and garbage, is dirty, rotten, and smelly, containing many pathogens or toxicants, making it a significant source of pollution.
Biological Fertilizers/Microbial Fertilizers
Advantages: They activate nutrients locked in the soil, stimulate root growth and absorption, and reduce the amount of fertilizer needed for these nutrients. Increasing beneficial bacteria in the soil can eliminate harmful bacteria, thereby reducing crop diseases!
Disadvantages: It contains little or no nitrogen, phosphorus, and potassium, and cannot provide long-term nutrition to crops. Because bacterial fertilizers are composed of living bacteria, they are generally protected from direct sunlight and cannot be mixed with pesticides. They also have strict requirements for environmental conditions such as soil temperature, humidity, pH, and organic matter content.
