Modern agriculture relies heavily on synthetic fertilizers to maintain high yields, but this comes at a cost. Unfortunately, a good chunk of the applied fertilizer isn’t even absorbed by crops. Instead, it leaches into the environment causing pollution.
Thankfully, nature offers a variety of materials that we can use to strengthen plants and soil, minus the harmful chemicals with artificial ingredients.
Keep reading to learn more about the best organic fertilizers and find out which one is the perfect match for your garden.
What are Organic Fertilizers?
Organic fertilizers are carbon-based natural substances that have been used by people for centuries. Most are sourced from animals, rock minerals, or plants. And while your crops can’t tell the difference between natural or synthetic fertilizers, there are plenty of reasons to go organic:
- Just like chemical products, organic fertilizers contain nitrogen (N), phosphorus (P), and potassium (K), along with other beneficial trace elements.
- They don’t contain any unhealthy artificial ingredients, making them a safer, sustainable product to use in your garden.
- You don’t have to worry about over-fertilization because most organic fertilizers have a slow-release mechanism.
- The gradual breakdown of organic matter nurtures the soil and improves its structure and microbial activity.
The best part is that there’s a wide variety of organic products to choose from. But, does it matter which one you pick and is there really any difference? Let’s take a closer look.
Compost: The King of Organic Fertilizers
- Organic compost is an all-purpose fertilizer suitable for most plants, especially vegetables and flowers.
- Best for general use in gardens and farms with all kinds of soil types.
- Ideal for mild to moderate climates.
- Apple right before planting and during the growing season.
Throughout history, composting has been integral to agriculture. A global practice known to farmers all the way from Stone Age Scotland to ancient China. And despite the many innovations that have made large-scale farming possible, compost remains a staple for growers across the world.
Compost is a recycled product, a mix of “greens” rich in nitrogen and “browns” rich in carbon. Leaves, food scraps, wood chips, and paper can all be composted and decompose into humus. The resulting mixture is packed with nutrients that are extremely beneficial to plants and the environment.
When applied it acts as a soil conditioner that introduces helpful microbes that reduce soil-bone diseases and suppress pathogens. It also increases the humus content of the soil for a long-lasting positive effect on the local ecosystem.
Humic Acids Fertilizer: Enhance Soil Properties
- Best for improving the structure and chemical properties of soils.
- Helpful for boosting the stress resilience of most plants.
- Particularly beneficial in sandy or clay soils.
- Effective in all climates, especially during drought or extreme weather conditions.
- Can be used at any time during the growing period, ideally mixed into the soil or as a top dressing.
Humic acids develop when organic matter decomposes through a process known as “humification.” This breakdown results in humus, consisting of humin, humic acids, and fulvic acids. Most frequently, they are found in sedimentation layers of soft brown coal, particularly leonardite.
As for the role of humic matter in agriculture, it acts as a biocatalyst to optimize nutrient absorption by plants. Their high cation-exchange capacity and exceptional moisture retention qualities actively prevent erosion and water runoff.
The unfortunate reality is that modern agriculture has disrupted the formation of humic matter in many farmlands. Typically, humus constitutes about 2% of healthy soil composition and is continually replenished in nature as part of the natural cycle. That is why you can find humic acid fertilizers on the market in many forms, most commonly granules, powder, and liquid.
Manure Fertilizers: A Time-Honored Tradition
- Best for supplying soil with organic matter and nutrients.
- An all-purpose option suitable for general gardening.
- Most efficient for well-draining acidic soils.
- Use in temperate climates with moderate rainfall.
- Always compost manure before using it to eliminate any present weed seeds and pathogens.
Some archaeological insights suggest manure’s fertilizing potential has been known to man for over 8000 years. Today, farmers continue using this tried-and-true organic matter to supplement their crops. And there’s plenty of reason for it.
Manure is made from decomposed animal waste, most frequently cow, horse, or poultry droppings. Similarly to compost, manure fertilizer is known for its nutrient-rich composition and balanced NPK ratio. In addition to that, it often contains a variety of microelements, such as iron, carbon, calcium, magnesium, and sulfur.
What makes manure particularly useful is its availability: animal factory farming produces it pretty much for free. The waste is then transformed into fertilizer that can be used to sustain fields and crops for cattle to eat, essentially closing the cycle.
If you happen to live in a rural area, you might be able to find locally-sourced manure. Just a word of caution though: certain types, such as chicken droppings have a high nitrogen content which can damage your plants if you’re not careful.
Seaweed Extract: A Versatile Organic Solution
- Seaweed serves as a natural bio-fertilizer, rich in micro and macronutrients, humic acids, and phytohormones.
- It’s a powerful supplement that works for all plant and soil types, no matter the pH levels.
- Seaweed extract fertilizers make your plants more resilient to extreme weather conditions, such as drought, heat, heavy rainfall, and even hailstorms.
- Apply as a seed soak, foliar spray, or a direct soil drench.
Algae has been used to feed livestock and wrap plant roots since ancient times. The earliest recorded agricultural use of seaweed dates back to the 2nd century in ancient Greece and Rome. Today, it is one of the best organic fertilizers that growers swear by.
Marine plants are a potent source of several vitamins and fatty acids that are commonly used for boosting seed germination. In fact, seaweed fertilizers are known to contain more trace minerals compared to those made from animal byproducts. The extract is obtained from various algae species through fermentation or industrial techniques using heat, pressure, or enzymes.
Bone Meal: A Phosphorus-Rich Powerhouse
- Best for providing nutrient-deficient plants with phosphorus.
- Most commonly used for flowering plants, alliums, and root crops.
- Should be applied in acidic soils with a pH below seven.
- Apply at planting time or during flowering.
Don’t be put off by the unappealing name—bone meal fertilizer is jam-packed with phosphorus, calcium, and nitrogen that your plants will love.
As you can probably guess, the product is made from finely ground animal bones. It can be mixed with water and applied directly to containers or garden beds through irrigation systems or as a slurry.
Because of its high phosphorus content, bone meal is most beneficial to edible and ornamental plants that need a boost during the flowering stage. But stay cautious—it’s best to apply this organic fertilizer in moderation, otherwise it might cause root damage.
Rock Phosphate: A Slow-Release Fertilizer
- A high-quality source of slow-release phosphorus.
- Suitable for all types of flowering plants, bulbs, shrubs, trees, and vegetables.
- Performs best in neutral to alkaline soils.
- Most efficient in regions with consistent moisture to properly break down and release phosphorus.
- Best applied mixed with soil before planting.
Organic rock phosphate fertilizer is a favorite of growers primarily because of its slow-release qualities. As the name suggests, it is extracted from rock and clay deposits rich in phosphorus.
Once applied to the soil, it steadily releases nutrients at an even rate throughout the growing season. The high phosphorus content supports essential metabolic functions in plants, most importantly the process of photosynthesis.
But here’s the uncomfortable truth: Phosphate rock is a finite resource and we are quickly depleting it. Nowadays, it’s better to switch to a more sustainable phosphorus source such as greensand fertilizer, which has a more diverse nutrient profile.
How to Choose the Best Organic Fertilizer for Your Needs?
As you can see there are plenty of natural products you can use to nurture your plants. But which one is right for you? Here are our tips for selecting the best organic fertilizer for your crops:
- Your choice of fertilizer depends on your soil’s pH, nutrient levels, and the specific NPK requirements of your plants. Just be cautious of fertilizers with high salt levels because they might cause plant burns.
- Take the local climate and your growing conditions into consideration. Slow-release products are more effective in wetter climates, while liquid fertilizers perform best in dry conditions.
- Keep in mind that organic fertilizers are typically applied at higher rates because they are less concentrated than inorganic types.
- The growth stage of plants matters too. Seedlings may require more phosphorus for root development, while mature plants need more potassium for fruit and flower production.
- Watch out for contaminants—some store-bought products marketed as “organic” may contain heavy metals, pesticides, or pathogens. Look for products that are Organic Materials Review Institute (OMRI) registered or otherwise certified by a reputable organization.
When considering the best organic fertilizer for your needs, it’s essential to evaluate options that not only nourish the soil but also integrate natural pest control methods, such as companion planting or beneficial nematodes, to ensure a sustainable and thriving ecosystem for your crops.
Conclusion
Achieving the right soil balance to grow a healthy, thriving garden can be quite a challenge. But correcting nutrient deficiencies in plants doesn’t have to come at the expense of our ecosystems. Hopefully, this overview of the best organic fertilizers gave you some ideas on how you can nurture your plants in an eco-friendly way. So, the next time you’re tending to your crops, consider going organic. You’ll be grateful when your garden rewards you with delicious and nutritious produce for years to come.
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