Sustainable fertilization has become one of the fundamental pillars for those seeking to maintain the health of their crops, gardens, and orchards. Organic fertilizers Fertilizers have taken center stage due to growing environmental concerns and the search for natural alternatives that restore and maintain soil fertility while ensuring healthy, high-quality production. In this comprehensive guide, we'll explore what they are, how they're classified, their main benefits compared to chemical fertilizers, and how to choose the most appropriate option based on the needs of each soil or crop.
What are organic fertilizers and why are they important?
The Organic fertilizers They are substances of natural origin, obtained from the decomposition of plant or animal waste or natural processes, whose main function is improve the chemical, physical and biological properties of the soilUnlike synthetic fertilizers, they are completely free of artificial chemicals and integrate perfectly into nature's cycle.
Among its main features are:
- they have animal, vegetable or mineral origin.
- They provide essential macronutrients such as nitrogen, phosphorus and potassium, as well as micronutrients and organic matter.
- They are products that require biological decomposition processes to make their nutrients available to plants.
- environmentally friendly and contribute to the conservation of soil biodiversity.
La importance of organic fertilizers This is because they facilitate nutrient recycling, promote microbial life, improve soil structure and water retention capacity, and allow for more balanced and sustainable crop development. Furthermore, their use reduces dependence on synthetic fertilizers, whose long-term effects can be detrimental to soil quality and surrounding ecosystems.
Key benefits of organic fertilizers versus chemical fertilizers
- Natural waste recycling: Organic fertilizers transform crop residues, animal excrement, and other byproducts into valuable fertilizer, promoting the circular economy and reducing waste.
- Activation of soil life: They promote the proliferation of essential microorganisms, bacteria and fungi that decompose organic matter and facilitate the progressive release of nutrients.
- Improving the physical structure of the soil: They increase porosity, sponginess and water retention capacity, facilitating aeration and water infiltration.
- Gradual nutrient supply: Slow release prevents fertilization peaks and minimizes risks of leaching or salt buildup.
- Less environmental impact: Since they do not contain synthetic chemicals, they do not generate contamination from leachates or toxic waste.
- Support for agricultural sustainability: They maintain and restore natural soil fertility, promote ecosystem resilience, and help mitigate erosion and land degradation.
- Long-term cost reduction: Self-generation of homemade fertilizers reduces dependence on external inputs and fosters farmer autonomy.
- Improving the quality and taste of products: Organically fertilized crops tend to have better flavor, higher nutritional content, and greater resistance to pests and diseases.
- Carbon sequestration and climate conservation: By increasing the organic matter content, soils have a greater capacity to capture and retain atmospheric carbon, contributing to the fight against climate change.
Classification of organic fertilizers according to their origin
The diversity of organic fertilizers can be grouped mainly into three large categories depending on the nature of their components: fertilizers of animal, vegetable and mineral originEach group offers specific characteristics and benefits, so it's important to understand them in detail to select the most appropriate one for your soil and crop type.
Animal-based fertilizers
These fertilizers are derived from animal waste and livestock or fishery byproducts. The best-known include:
- Cattle manure: It can come from cow, horse, sheep, goat, pig, or poultry (chicken manure). Its composition varies depending on the species, diet, management, and maturation. It is notable for its contribution of nitrogen, phosphorus, potassium, calcium, and organic matter. It is essential to compost manure before applying it to avoid phytotoxicity or pathogen problems.
- Bat guano: Considered a highly concentrated fertilizer, very rich in nitrogen, phosphorus, and micronutrients. Ideal for flowering plants and demanding crops.
- Dried blood and bone meal: Slaughterhouse by-products with a high nitrogen content (dried blood) and phosphorus/calcium content (bones), respectively. Dried blood is used especially for green leafy crops, and bone meal is used to stimulate root development and flowering.
- Feather meal and other by-products: Feather meal is a source of slow-release nitrogen. There are also liquid fertilizers derived from fish emulsions or fish hydrolysates, which provide rapidly assimilated macronutrients and trace elements.
- Animal urine: Although less used, it contains nitrogen, phosphorus and potassium in concentrations that can be used with proper management.
Proper handling and composting are crucial to avoid health risks and ensure the complete decomposition of organic matter before incorporating it into the soil.
Fertilizers of plant origin
Plant fertilizers are obtained from crop residues, leaves, branches, flowers, seeds, and agricultural byproducts. They are notable for being quick to decompose, promoting soil structure, and providing a considerable amount of nutrients, especially potassium and organic matter.
- Compost: Composting is a product of the fermentation and aerobic decomposition of organic plant (and sometimes animal) remains. Composting produces a fertilizer rich in nutrients, microorganisms, and humus, essential for soil fertility and health.
- Worm humus (vermicompost): It is produced by the digestive activity of earthworms on organic matter. It offers a very balanced nutritional profile and numerous beneficial microorganisms. It provides nitrogen, phosphorus, potassium, and compounds that stimulate the natural resistance of plants.
- Green manures: It involves planting certain plant species (legumes, grasses, or cruciferous vegetables) and then harvesting and incorporating them into the soil. They improve texture, fix atmospheric nitrogen, prevent erosion, and provide rapidly biodegradable organic matter.
- Seed flour, gluten and agricultural by-products: Alfalfa, soybean, cottonseed, and corn gluten meal are rich in nitrogen and potassium. Alfalfa meal also contains natural phytohormones that stimulate plant growth.
- Plant extracts and macerates: Seaweed, nettle, and comfrey stand out for their contribution of trace elements, phytohormones, and stimulating or biostimulant properties.
- Vegetable ashes: Rich in potassium and micronutrients, recommended for correcting acidic soils and providing minerals.
- Peat: A slow-decomposing plant product that improves soil structure and water retention, although its use must be sustainable to avoid damaging peatland ecosystems.
Mineral fertilizers
Although traditionally organic is considered to be that which comes from living beings, in the field of organic agriculture some natural minerals They are also accepted as organic fertilizers, as they have not been subjected to industrial chemical processes. Highlights include:
- Rock phosphate: Natural and economical source of slow-release phosphorus.
- Langbeinita: Provides potassium, magnesium and sulfur with high solubility for plants.
- Sand/greensandstone: Excellent amendment for soils with poor mineral reserves, especially potassium.
- Ground limestone: Used to correct soil pH and provide calcium in a sustainable way.
- Rock dust: It allows to replenish a wide range of micronutrients and trace elements.
These natural mineral fertilizers are especially recommended for depleted soils or to balance nutrition in demanding crops.
Organic fertilizers according to the format and application method
In addition to their origin, organic fertilizers are classified according to their Physical format and application mode:
Solid organic fertilizers
They represent the most common and traditional form of fertilizer. They can be applied directly to the soil or incorporated during tilling. Their main forms are:
- Ground or powdered: It easily integrates with the soil or can be mixed with irrigation water for localized applications.
- Granulated: Medium-sized particles, especially useful for slow-release contributions in long-cycle crops.
- Pellet: Compressed fertilizer in small cylinders or granules, ideal for convenient, clean, and long-lasting application.
- Organic amendments: Compost, worm castings, bokashi, and other stabilized products can be spread, mixed, or buried as needed.
Liquid organic fertilizers
Its use has spread thanks to its ease of application and rapid absorption:
- Liquid concentrates: They need to be diluted beforehand and allow dosages adjusted to the needs of the crop.
- Ready to use: Low concentration solutions for direct applications, especially in pots or young plants.
- Fertigation: Application together with irrigation water, achieving uniform and continuous distribution.
- Foliar: Products specially developed to be absorbed by the leaves, providing immediate action for specific deficiencies.
- Compost tea and worm tea: Liquid infusions resulting from the maceration of compost or worm castings, rich in microorganisms and bioavailable nutrients. Ideal for strengthening plants and restoring microbial life in the soil.
Fertilizers according to the rate of nutrient release
The choice of fertilizer also depends on the rate or speed of nutrient availability:
- Slow release: Large solids and residues that are difficult to degrade. They provide nutrients continuously over a long period, promoting the restoration of depleted or infertile soils.
- Fast acting: Liquid fertilizers, soluble powders, and concentrates that correct deficiencies almost immediately. They are ideal for nutritional emergencies or to reinforce critical growth stages (germination, flowering, fruiting, etc.).
Comparative table of nutrients in different organic fertilizers
| Fertilizer type | Nitrogen (kg/t) | Phosphorus (kg/t) | Potassium (kg/t) | Calcium (kg/t) | Organic Matter (kg/t) |
|---|---|---|---|---|---|
| Bovine manure | 14,2 | 14,6 | 34,1 | 36,8 | 510 |
| Chicken manure | 34,7 | 30,8 | 20,9 | 61,2 | 700 |
| Compost | 0,9 | 0,7 | 1,0 | 2,7 | 6.540 |
This table demonstrates the differences in fertilizer composition and the need to adjust the amounts according to crop type, soil, and fertilization objective. To expand your knowledge about types of nitrogen-rich fertilizers.
Potential disadvantages and usage considerations
Despite their countless advantages, it is important to consider some limitations of organic fertilizers:
- Variability in nutrient content: Values ​​may fluctuate depending on the origin, handling and composition of the waste.
- Slow and unpredictable release in soils with little microbial life: In degraded soils, it is recommended to inoculate microorganisms or use compost teas. You can find more information at all about fertilizers.
- Health risk: Improper use of fresh manure can transmit diseases. Waste should always be composted and aged before application.
- Low concentration compared to chemical fertilizers: To achieve the same amount of nutrients, larger volumes of fertilizer may be required.
How to make homemade organic fertilizer: steps and recommendations
Making homemade compost is a simple and sustainable practice that allows you to use kitchen, garden, and pruning waste. The basic steps for making compost are:
- Gather the right materials: Use plant waste such as fruit and vegetable peels, dried leaves, grass, cardboard, and, to a lesser extent, animal waste (avoid meat, fish, and dairy products due to odor and health risks). To learn more, visit list of organic fertilizers.
- Select the location: A dedicated composter, a soil pile, or a flowerbed composter are all valid options, provided they provide adequate ventilation to prevent anaerobiosis.
- Toggle layers: Place layers of dry matter (cardboard, dry branches) and moist layers (fresh remains), covering with soil between each addition.
- Aerate regularly: Turn the pile with a rake or similar once a week to promote oxygenation and prevent unpleasant odors or compaction.
- Control humidity: The mixture should maintain a moisture level similar to that of a wrung-out sponge. If it's too dry, add water. If it's too wet, add more dry matter.
- Maturation: After 3 to 6 months, the compost will be ready when it acquires a dark color, earthy texture, and a pleasant smell of fertile soil.
The making of earthworm humus requires incorporating Californian red worms into the compost bed to speed up the process and further enrich the final product. You can find out more at rowan.
They can also be prepared slurry and fermented extracts (for example, nettle or comfrey) by maceration and anaerobic fermentation, which once filtered are useful as foliar fertilizers or for fertigation.
Practical application and recommendations according to crop type
Selecting the most suitable organic fertilizer depends on the needs of the crop, the characteristics of the soil and the time of year:
- For very poor soils, apply mature compost or well-rotted manure at high doses, preferably before sowing or planting.
- For demanding crops (vegetables, fruit trees, high-demand ornamentals), combine solid base fertilizers with foliar or liquid fertilizers at key times.
- In gardens and lawns, apply surface applications of compost or worm castings to improve structure and stimulate microbial life.
- For pots and indoor plants, use ready-to-use liquid fertilizers or diluted compost teas every 2-4 weeks.
- For crop rotations or agroecological systems, use green manure and the addition of crop residues to maintain the organic matter cycle.
Frequently asked questions about organic fertilizers
- Can I mix different organic fertilizers? Yes, as long as they are well-ripened and suited to the crop's needs. Mixing can improve the diversity of nutrients and microorganisms.
- How much organic fertilizer should I apply? It varies depending on the type of fertilizer, crop, and soil. As a general guideline, we recommend between 1 and 5 kg/m² of compost or mature manure, adjusting according to soil analysis.
- Does organic fertilizer completely replace chemical fertilizer? It is possible, especially in organic systems, although in very poor soils they can be used in combination during the transition period.
- Do they have an expiration date? Properly stored compost and humus maintain their properties for months, although they are best applied during the active growing season.
Organic fertilizers are indispensable allies for farmers, gardeners, and anyone seeking an ecological and effective alternative to synthetic fertilizers. Their responsible and appropriate use helps maintain soil health, produce healthier and more sustainable crops, and actively contribute to environmental restoration and the climate resilience of our productive environments.
