The Smart Gardener’s Guide: 4 Low-Cost Organic Fertilizers

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Regardless of what you’re growing, your plants need nutrients. Without fertilizer, your plants will fail to thrive and grow big and strong. In the case of edibles, a lack of nutrients can limit your crop and lead to poor production. Unfortunately, many fertilizers on the market are expensive. Thankfully, there are cheap organic fertilizers you can use to boost your garden’s productivity.

A Word of Caution

Before I jump into a list of cost-effective organic fertilizer suggestions, I want to talk a bit about fertilizing in general. Piling on fertilizer will NOT automatically make your garden more lush and productive. Fertilizing without testing your soil first can lead to a host of problems down the road. With fertilizer, more is not always better.

Always test your soil first to find out whether your garden is lacking nutrients. Read up about plant nutrient needs to ensure you’re applying the right fertilizer.

While organic fertilizer is a lot less harmful to the environment than synthetic fertilizer, too much of it can still pose problems, so be cautious! If you think your plants are hungry for nutrients, double-check first. They may be stressed or ailing for a different reason.

Organic fertilizers are an excellent alternative to synthetic ones because they help build soil quality over time and improve the soil’s ability to retain nutrients and water. They’re a lot less concentrated, which helps prevent overfertilization—though it’s still possible with certain commercial options.

Cheap Organic Fertilizers

Fertilizers can be expensive. Organic options are even more so! So what are the options available for a frugal gardener? Here are a few cost-effective organic fertilizers to choose from:

1. Worm Castings 

Set up a worm farm or attract worms using a bucket system and enjoy the fruits of their labor. Castings is a nice way of saying poop, but this excrement is mighty powerful! Worm poop is high in nitrogen and full of beneficial microbes and bacteria.

DIY Recipe:

• Start a worm bin using a plastic tote or wooden box.
• Add bedding (shredded newspaper, cardboard, or coco coir).
• Feed worms with kitchen scraps like fruit peels, coffee grounds, and vegetable trimmings.
• Harvest castings every 2–3 months by separating worms from the compost.

Yield Information:

• 1 pound of worms can produce about 1 pound of castings per month.
• Castings improve soil structure, boost microbial activity, and increase nitrogen availability.

2. Coco Coir

Coconut husks are an inexpensive, earth-friendly alternative to peat moss. While coir doesn’t contain nutrients, it helps condition the soil and improves water and nutrient retention.  It’s also a great mulch option.

DIY Recipe:

• Purchase compressed coco coir bricks (widely available and inexpensive).
• Soak the brick in a bucket of water until it expands.
• Mix into soil at a ratio of 1 part coir to 2 parts soil for improved aeration and water retention.

Yield Information:

• Coco coir doesn’t add nutrients but can increase water retention by up to 60%, reducing the need for frequent watering.
• Helps stabilize yields in drought-prone areas.

3. Homemade Compost 

It’s easy to make your own compost at home! You’ll need a balanced mix of kitchen scraps and other materials like dead leaves and grass clippings to get some rotting action going. Over time, the materials break down into a powerhouse of nutrients for your garden.  Be careful, though – sometimes the compost can attract squirrels, or other vermin that live in the rotting vegetable matter, such as flies.   If you live in an urban area, get a covered compost bin to avoid problems.

DIY Recipe:

• Combine “greens” (fruit/vegetable scraps, coffee grounds, grass clippings, egg shells) with “browns” (leaves, shredded paper, cardboard).
• Aim for a 2:1 ratio of browns to greens.
• Keep the pile moist and turn it weekly to aerate.
• Compost is ready in 2–6 months when it’s dark, crumbly, and earthy-smelling.

Yield Information:

• A well-managed compost bin can produce 20–40 pounds of compost per cubic yard every season.
• Compost enriches soil with nitrogen, phosphorus, potassium, and micronutrients, boosting crop yields by up to 30% compared to unfertilized soil.

4. Seaweed 

Sea kelp fertilizer is pricey, but if you live near a shoreline, you can collect your own smelly seaweed, let it rot for a bit, and make a seaweed fertilizer tea. It’s not ideal for people who are sensitive to pungent smells, but it’s a great, totally free source of nutrients!

DIY Recipe:

• Collect fresh seaweed (avoid polluted areas).
• Rinse thoroughly to remove excess salt.
• Chop and soak in a bucket of water for 2–3 weeks, stirring occasionally.
• Strain and use the liquid as a foliar spray or soil drench.

Yield Information:

• Seaweed tea provides potassium, magnesium, and trace minerals.
• Studies show seaweed fertilizer can increase vegetable yields by 15–20% and improve plant resilience against pests.

For those of you who learn better with video, here is a great one on how to make seaweed fertilizer.

5. Enviro Ice (Bonus Tip)

If you are getting packages coming to your house, they might have Enviro Ice in them. You can use Enviro Ice as a fertilizer – you just need to dilute it a bit. We’ve covered how to use it here on the blog.

DIY Recipe:

• If you receive packages with Enviro Ice packs, cut them open.
• Dilute the contents with water at a 1:4 ratio.
• Apply directly to the soil as a nitrogen-rich fertilizer.

Yield Information:

• Provides a quick nitrogen boost, encouraging leafy growth in vegetables like lettuce, spinach, and kale.
• Can increase early-season yields by 10–15% when used sparingly.

Growing More With Less

Organic fertilizers don’t have to drain your wallet. With a little creativity, you can turn everyday waste—worms, kitchen scraps, seaweed, even shipping ice packs—into powerful soil amendments. These DIY recipes not only save money but also improve soil health, water retention, and long-term productivity. By testing your soil first and applying the right fertilizer, you’ll maximize yields while keeping your garden eco-friendly and sustainable.

What to Read Next

• Should I Use Enviro Ice On My Plants?
• 5 Gardening Practices That Are Harming the Environment
• Top 13 Benefits of Using Rice Hulls in Gardening
• Don’t Do That! 9 Pieces of Bad Gardening Advice to Ignore

Steph Coelho

Steph Coelho is a freelance writer gardening in zone 5b. She is a certified Square Foot Gardener and has taught various garden-related workshops. When she’s not digging in the dirt or writing, she’s cooking up fresh produce, running, or listening to her favorite podcasts.