Best Organic Nutrients for Soil: 10 Castings, Composts and Organic Fertilizers Compared

Healthy, productive gardens begin with soil that provides the right balance of nutrients, organic matter, and beneficial microorganisms. Over time, growing plants can use up essential nutrients, leaving garden beds less productive if the soil isn’t replenished. Organic fertilizers and soil amendments offer a way to support plant growth while improving soil structure and long-term fertility.

For gardeners looking for a gentle nutrient source, Wiggle Worm Castings 15 lb provides worm castings containing nutrients and beneficial microbes. The Jobe’s Organics 4-4-4 offers a balanced granular fertilizer with equal proportions of nitrogen, phosphorus, and potassium. Meanwhile, Andersons HumiChar 12 lb focuses on adding carbon-based amendments to support long-term soil improvement.

In this guide, we examine 10 organic soil nutrients and amendments, comparing their formulations, NPK ratios, package sizes, and OMRI listing status using available product specifications. Whether you’re preparing vegetable beds, maintaining flower gardens, or improving tired soil, understanding these differences can help you select the right product. For the best results, consider testing your soil before adding nutrients so you can address actual deficiencies rather than applying fertilizers your garden may not need.

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On this page

1. Compare Organic Soil Nutrients by Type, NPK, Size and OMRI Listing
2. Detailed Reviews: Best Organic Nutrients for Soil
3. Feed the Soil and the Plant, Not Just One
4. Follow the Rate on the Label
5. How to Choose Organic Nutrients for Soil
6. Which Organic Soil Nutrient Should You Choose?
7. Frequently Asked Questions
8. Final Verdict

Compare Organic Soil Nutrients by Type, NPK, Size and OMRI Listing

Detailed Reviews: Best Organic Nutrients for Soil

1. Wiggle Worm 100% Pure Organic Worm Casting Fertilizer, 15 lb (Best overall soil booster)

• 15 lbBag
• OMRIListed
• Half cupPer plant
• 3 timesPer year

Best for: vegetable beds, houseplants and transplants that need gentle feeding with no risk of burn

Why it ranks #1: It improves both nutrients and soil structure with a tiny dose, which edges out the stronger but narrower Jobe’s Organics 4-4-4.

Wiggle Worm sells 100% pure worm castings, not vermicompost or leftover worm bedding. The castings are OMRI listed and mineral dense. Wiggle Worm says it is one of the few castings products recognized as a fertilizer.

The castings are tiny, football-shaped particles that loosen dense soil and help loose soil hold water. Wiggle Worm suggests a handful or half a cup per plant, worked in above the root zone three times a year or added to the planting hole. It is odorless, so it also works indoors.

Skip it if you need a measured NPK for heavy feeders; the Jobe’s Organics 4-4-4 lists 4-4-4.

2. Jobe’s Organics Granular All Purpose Fertilizer 4-4-4, 16 lb Bag (Best all purpose organic fertilizer)

• 4-4-4NPK
• 16 lbBag
• OMRIListed
• 2 to 3 weeksReapply

Best for: gardeners feeding a mixed yard of vegetables, flowers and shrubs from one bag

Why it ranks #2: It gives the clearest NPK and the biggest bag, but it feeds plants more than it builds soil, unlike the Wiggle Worm Castings 15 lb.

Jobe’s Organics all purpose fertilizer comes in a 16 lb bag of granules with a balanced 4-4-4 NPK. It contains no synthetic chemicals and is OMRI listed for organic gardening. Jobe’s says the granules are made to cut down on runoff, mess and smell.

You can use it on vegetables, flowers, shrubs and trees. The listing says to apply every 2 to 3 weeks or as needed during the growing season, and that the granules are easy to measure so you do not overfeed. Follow the bag label for rates.

Skip it if you want to feed less often; the Miracle-Gro Organic 3 lb feeds up to 3 months.

3. Dr. Earth Organic 5 Tomato, Vegetable and Herb Fertilizer (Best for tomatoes and vegetables)

• 7Microbe strains
• Ecto and endoMycorrhizae
• Several monthsFeeding
• No GMOsIngredients

Best for: tomato, pepper and herb growers who want food and soil microbes in one product

Why it ranks #3: It adds more soil life than the Jobe’s Organics 4-4-4, but the listing gives no NPK or bag size.

Dr. Earth Organic 5 is made for tomatoes, vegetables and herbs from 100% organic and natural ingredients. Dr. Earth says it carries the main plant nutrients at the right levels for food crops and feeds for several months.

Each bag includes seven strains of beneficial soil microbes plus ecto and endo mycorrhizae, which help roots take up water and nutrients. Dr. Earth says it contains no GMOs, chicken manure or sewage sludge. The listing does not state the NPK or the bag size, so check the label.

Skip it if you want a stated NPK; the Down to Earth Veg 4-4-4 lists 4-4-4 for vegetables.

4. The Andersons HumiChar Organic Soil Amendment with Humic Acid and Biochar, 12 lb (Best long-term soil builder)

• 12,000 sq ftCoverage
• 30%Humic acid
• 43%Biochar
• OMRIListed

Best for: large lawns and garden beds with tired soil where you want lasting carbon

Why it ranks #4: It covers the most area and builds soil for years, but it is an amendment, not a fertilizer like the Jobe’s Organics 4-4-4.

HumiChar from The Andersons is an organic, carbon-based soil amendment with 30% humic acid and 43% granulated biochar. The humic acid acts quickly, while the biochar builds soil structure that The Andersons says lasts for decades. One 12 lb bag covers 12,000 sq ft.

The spherical, low-dust granules use The Andersons’ dispersible granule technology to break down fast. You can spread it alone or blend it with your fertilizer. It is OMRI listed. The listing notes it is not for sale in California or Oregon.

Skip it if you need plant food now; the Jobe’s Organics 4-4-4 supplies 4-4-4.

5. Brut Cow Compost, Composted Cow Manure Organic Soil Amendment, 10 Quart (Best pure compost)

• 10 qtBag
• OMRIListed
• N, calcium, ironNutrients
• Finely siftedTexture

Best for: top dressing pots, seedlings and delicate flowers that need gentle organic matter

Why it ranks #5: It is pure, sifted and OMRI listed, but the 10 qt bag covers less ground than the R&M Organics Compost 10 lb.

Brut Cow Compost is made only from thoroughly composted cow manure, aerated and screened for safety. Brut says it carries nitrogen, calcium and iron and boosts microbial life. The finely sifted texture blends easily into pots and beds.

Brut says it is odor-free and gentle enough that it will not burn roots, even on seedlings and houseplants. Use it as a top dressing, mix it into potting soil or work it into garden beds. It is OMRI listed and comes in a 10 qt bag.

Skip it if you are amending large beds; the R&M Organics Compost 10 lb comes in a 10 lb bag of dairy compost.

6. Down to Earth Organic Vegetable Garden Fertilizer 4-4-4, 5 lb (Best slow release vegetable food)

• 4-4-4NPK
• 5 lbBox
• Slow releaseFormula
• Raised bedsUse

Best for: raised bed vegetable gardens where you want steady feeding without leaching

Why it ranks #6: It matches the Jobe’s Organics 4-4-4 on NPK with a slow release, but in a smaller 5 lb box.

Down to Earth makes this vegetable garden fertilizer with a balanced 4-4-4 NPK for roots, leaves and fruit. It comes in a 5 lb box that you sprinkle on the soil or mix into beds before planting.

The slow release formula feeds plants gradually and reduces leaching. Down to Earth says it is made from organic materials and is non-toxic to beneficial insects, pollinators and pets when used as directed. It suits vegetables, herbs and greens in raised beds.

Skip it if you feed a large yard; the Jobe’s Organics 4-4-4 comes in a 16 lb bag.

7. Essential Soils OG Organic Super Soil Concentrate, Living Soil, 5 lb (Most ingredients)

• 16Ingredients
• 5 lbBag
• MycorrhizaeAdded
• CaliforniaMade in

Best for: container and raised bed growers who mix their own living soil

Why it ranks #7: It has the widest ingredient list here, but no NPK or rates, which keeps it behind the Down to Earth Veg 4-4-4.

Essential Soils OG Organic is a living super soil concentrate built from 16 organic ingredients, including worm castings, bat guano and kelp meal. It is inoculated with mycorrhizal fungi and beneficial bacteria that work with your soil’s own biology.

Use it for direct potting, top dressing, amending soil mixes, raised beds or containers. A small California company makes it. The listing gives no NPK or mixing rate. Wear a dust mask when you mix it, since guano and dry blends can be dusty.

Skip it if you want simple rates; the Miracle-Gro Organic 3 lb lists cups per square foot.

8. Miracle-Gro Organic All Purpose Plant Food, 3 lb, OMRI Listed (Clearest application rates)

• Up to 3 monthsFeeding
• 3/4 to 1 cupPer 20 sq ft
• 1 tbspPer 6 in pot
• 3 lbBag

Best for: beginners who want simple measurements for containers and small beds

Why it ranks #8: It has the clearest rates and longest feed time, but its 3 lb bag is the smallest fertilizer here.

Miracle-Gro Organic All Purpose Plant Food is an OMRI listed granular fertilizer that feeds for up to 3 months. It works on vegetables, flowers, annuals and perennials in the ground or in containers.

The rates are simple. About 3/4 to 1 cup covers 20 sq ft of bed, and 1 tablespoon feeds one 6 in pot. Shake the granules on the soil, mix them into the top 1 to 3 in, then water. The listing does not state the NPK.

Skip it if you have a big garden; the Jobe’s Organics 4-4-4 comes in 16 lb.

9. Farmer’s Secret Soil Revitalizer, Organic Liquid Humic Soil Amendment, 32 oz (Best liquid soil booster)

• 32 ozBottle
• 1 oz per galDilution
• MonthlyApplication
• KentuckyMade in

Best for: gardeners who want to wake up soil life in spring and fall with a watering can

Why it ranks #9: It is the only liquid here and easy to apply, but it feeds soil microbes rather than plants, unlike the Miracle-Gro Organic 3 lb.

Farmer’s Secret Soil Revitalizer is a liquid soil amendment whose main ingredient is activated humics from organic sources. It is OMRI certified. The idea is to feed the soil, not the plant, and stimulate microbes much like compost but faster.

Dilute 1 oz per gallon of water, then spray or pour it on the soil. Farmer’s Secret suggests monthly use through the growing season, especially in spring and fall. The 32 oz bottle makes up to 32 gallons. It is made in Kentucky.

Skip it if you want a one-time spread; the Andersons HumiChar 12 lb builds soil for years.

10. R&M Organics Compost Soil Amendment, Dairy Cow Manure Base, 10 lb (Best moisture-holding compost)

• 10 lbBag
• Dairy manureBase
• 1/4 inTop layer
• Low odorScent

Best for: sandy beds and pots that dry out fast and need organic matter

Why it ranks #10: It helps soil hold water, but the listing gives no organic certification, so it ranks below the OMRI listed Brut Cow Compost 10 Qt.

R&M Organics makes this compost from dairy cow manure. It is fully composted with constant aeration, which the listing says leaves a clean, earthy smell. It replaces nutrients that crops use up and improves soil texture.

The listing says it helps soil retain moisture longer, which can cut down on watering. Spread a layer about 1/4 in thick around plants or mix it into new beds and pots. The 10 lb bag suits small to medium projects. Wash vegetables well before eating, as with any manure product.

Skip it if you want a certified organic compost; the Brut Cow Compost 10 Qt is OMRI listed.

Feed the Soil and the Plant, Not Just One

The most common mistake is treating fertilizer and soil amendments as the same thing. A fertilizer like the Jobe’s Organics 4-4-4 feeds this season’s plants. An amendment like the Andersons HumiChar 12 lb or compost like the Brut Cow Compost 10 Qt builds the soil those plants grow in.

Gardens do best with both. Castings like the Wiggle Worm Castings 15 lb sit in the middle, adding mild nutrients and improving structure at the same time.

Rule of thumb: once a year, work 1 to 2 in of compost or a few cups of castings into beds. Then use a measured fertilizer during the season as plants need it. Poor, sandy soil benefits most, and so do tough plants like these drought tolerant perennials for poor soil when you plant them.

Follow the Rate on the Label

Organic does not mean you cannot overdo it. Too much nitrogen gives you leafy plants with few fruits, and extra nutrients can wash into streams.

Use the numbers on the bag. Miracle-Gro says about 3/4 to 1 cup of the Miracle-Gro Organic 3 lb covers 20 sq ft. Farmer’s Secret dilutes the Farmer’s Secret Soil Revitalizer at 1 oz per gallon. Wiggle Worm suggests about half a cup of the Wiggle Worm Castings 15 lb per plant.

Wear gloves when you handle fertilizers and manure, and wash your hands afterward. Store bags closed and away from pets, since some dogs like the smell of meal-based feeds. Rinse vegetables before eating if you used manure compost.

How to Choose Organic Nutrients for Soil

Fertilizer or amendment

Pick a fertilizer with a listed NPK, like the Jobe’s Organics 4-4-4 or Down to Earth Veg 4-4-4, to feed plants. Pick an amendment like the Andersons HumiChar 12 lb or R&M Organics Compost 10 lb to improve soil texture and carbon.

NPK

A balanced 4-4-4 suits most vegetable beds. Only the Jobe’s Organics 4-4-4 and Down to Earth Veg 4-4-4 list NPK in their features, so read the bag on the others.

Soil life

Microbes and mycorrhizae help roots take up nutrients. The Dr. Earth Organic 5 Veg Food adds 7 microbe strains, and the Essential Soils Super Soil adds mycorrhizal fungi and bacteria.

Format

Granules last longest. Liquids like the Farmer’s Secret Soil Revitalizer act fast and apply with a watering can. Compost like the Brut Cow Compost 10 Qt works as a top dressing.

Coverage

The Andersons HumiChar 12 lb covers 12,000 sq ft per bag, while the Miracle-Gro Organic 3 lb covers about 20 sq ft per cup. Measure your beds before you buy.

Which Organic Soil Nutrient Should You Choose?

• If you want one product that feeds and builds soil, choose the Wiggle Worm Castings 15 lb, because pure castings do both gently.
• If you want a balanced all purpose feed, choose the Jobe’s Organics 4-4-4, because it is 4-4-4 in a 16 lb bag.
• If you grow tomatoes and herbs, choose the Dr. Earth Organic 5 Veg Food, because it adds 7 microbe strains and mycorrhizae.
• If your soil is tired and compacted, choose the Andersons HumiChar 12 lb, because it adds humic acid and long-lasting biochar.
• If you need a gentle top dressing, choose the Brut Cow Compost 10 Qt, because it is sifted, OMRI listed cow compost.
• If you garden in raised beds, choose the Down to Earth Veg 4-4-4, because its slow release 4-4-4 is made for vegetables.
• If you mix your own living soil, choose the Essential Soils Super Soil, because it has 16 organic ingredients.
• If you want simple measurements, choose the Miracle-Gro Organic 3 lb, because it lists cups per bed and spoons per pot.
• If you prefer liquids, choose the Farmer’s Secret Soil Revitalizer, because you dilute 1 oz per gallon.
• If your soil dries fast, choose the R&M Organics Compost 10 lb, because it helps soil hold moisture.

Frequently Asked Questions

What are the best organic nutrients for soil?

Worm castings are the best all-round choice for most gardens, and the Wiggle Worm Castings 15 lb is pure, OMRI listed castings. For measured plant food, the Jobe’s Organics 4-4-4 gives a balanced 4-4-4. Many gardeners use both: castings to build soil and a fertilizer during the growing season.

Worm castings vs compost: which is better?

Both add organic matter. Castings like the Wiggle Worm Castings 15 lb are finer and richer in microbes, so you need less. Compost like the Brut Cow Compost 10 Qt or R&M Organics Compost 10 lb adds more bulk, which helps sandy or clay soil hold water and drain. Use compost to build volume and castings as a boost.

What does NPK 4-4-4 mean?

It means 4% nitrogen, 4% phosphate and 4% potash by weight. Nitrogen drives leaves, phosphorus helps roots and flowers, and potassium supports overall health. The Jobe’s Organics 4-4-4 and Down to Earth Veg 4-4-4 both list a 4-4-4 ratio, which suits most mixed vegetable beds.

How often should I add organic nutrients to soil?

Add compost or castings once or twice a year, often in spring and fall. Feed with fertilizer as the label says. Wiggle Worm suggests its Wiggle Worm Castings 15 lb three times a year, Jobe’s lists every 2 to 3 weeks for the Jobe’s Organics 4-4-4, and Miracle-Gro says the Miracle-Gro Organic 3 lb feeds up to 3 months.

Are organic fertilizers safe for pets and kids?

Many are lower risk than synthetic feeds, but read every label. Down to Earth says the Down to Earth Veg 4-4-4 is safe for pets and pollinators when used as directed. Keep bags sealed, water granules into the soil after spreading, and keep pets off treated beds until the surface dries.

What is humic acid and biochar for?

Humic acid helps soil hold nutrients and water, and biochar is a stable carbon that gives microbes a home for years. The Andersons HumiChar 12 lb combines 30% humic acid with 43% biochar, and the liquid Farmer’s Secret Soil Revitalizer supplies activated humics you water in.

Final Verdict

The Wiggle Worm Castings 15 lb is the best of the organic nutrients for soil in most gardens. These OMRI listed pure castings improve structure, add microbes and feed plants gently, and half a cup per plant goes a long way. If you want a measured fertilizer, the Jobe’s Organics 4-4-4 is the better pick with its 4-4-4 NPK. Before you buy, test your soil so you know what it lacks.

See the Wiggle Worm Castings 15 lb on Amazon