THE Official Sow True Seed Soil Amendment Cheat Sheet

Soil amendments fall into three broad categories: fertilizers, soil conditioners, and biostimulants. Fertilizers provide one or more of the major plant nutrients, nitrogen, phosphorus, and potassium. The three numbers on amendments (written 0-0-0) refer to the percentage of Nitrogen, Phosphate, and Soluble Potassium respectively. Soil conditioners improve soil texture or nutrient holding capacity, or change the pH. Biostimulants encourage healthy microbial activity. This list categorizes amendments by their main uses, but many of them actually have multiple effects. You’ll also see that a lot of these amendments are labeled “Slow Release.” This is fairly common for organic fertilizers, though there are organic fast release fertilizers as well. Slow release amendments feed the soil as well as the plants, offering many benefits such as increasing organic matter, aeration improvements, drainage, microbial life, the list could go on. This also means that these amendments can take a while to start offering their benefits (the length of time often depends on the amendment), so consider amending your soil as early as Autumn, though starting 6-8 weeks before planting in Spring is fine as well.  

Fertilizers

Balanced/ All Purpose:

Worm Castings

• Improves soil structure and water retention

• Promotes beneficial microbial activity

• 100% non-toxic, and will never burn your plants unlike other animal manures!

Neversink Blend

• A mixture of feather meal, fish meal, alfalfa meal, kelp meal, and humic to create a balanced plant food.

• Humic has been known to increase germination rates, aid in breaking up clay and compacted soil, support the transfer of nutrients between soil and plant, and improve water retention! 

• Can also be used as a compost activator.

Cottonseed Meal (6-2-2)

• A plant-derived source of organic nitrogen, phosphorus, and potassium.

• Good all purpose fertilizer for acid-loving crops (blueberries, strawberries, rhododendrons, potatoes, roses).

• Slow release. 

• Adds enriched organic content that helps aerate dense soil while feeding your plants! 

Alfalfa Meal (3-2-2)

• Plant-derived all-purpose fertilizer, organic and vegan alternative to blood meal.

• Increases organic matter in the soil. 

• Encourages beneficial microbes and earthworms that break down nutrients and make them available for plants. 

• Flowering plants especially respond well to Alfalfa. 

• Compost pile stimulant: decomposes rapidly and creates heat which helps the rest of your compost to decompose, making more nutrients available to your plants. 

Fish Bone Meal (5-16-10)

• Fish Bone Meal provides 5% nitrogen, 16% phosphorus, and 14% calcium. General purpose fertilizer. Compared to Fish Meal, Fish Bone Meal provides slightly different levels of macro-nutrients.

High Nitrogen:

Nitrogen stimulates green growth for lush and healthy plants. Too much nitrogen can harm plants though, so follow application instructions, and only apply where needed!

Plant-Based Fertilizer Soluble (13-0-0)

• Vegan Fertilizer is a water soluble, organic, plant derived source of nitrogen. 

• Will not burn plants or cause salt to accumulate.  

Feather Meal (13-0-0)

• Made from sterilized poultry feathers that are dried and ground. 

• Slow-release nitrogen source.

• Great for tomatoes, corn, peppers and other heavy-feeding plants. 

Blood Meal (12-0-0)

• Highly concentrated nitrogen amendment. 

• Can also raise the acidity of your soil which is good for acid loving plants! 

• Blood meal is useful for beds that have had repeated plantings where the nitrogen has been drained.

Fish Meal (10-3-2)

• All-purpose organic fertilizer that helps to promote vigorous root development and rapid growth for flowers, veggies, trees, and shrubs. 
• This amendment is high in protein, making it an excellent choice for stimulating microbial life in the soil. 

High Phosphorus:

Phosphorus is one of the primary nutrients responsible for proper root development and the healthy production of flowers and fruits. It is especially helpful for growing root crops as well as fruiting crops. Phosphorus in the soil is also helpful in reducing transplant shock. 

Bone Meal (2-14-0)

• Provides a natural source of phosphorus and calcium for gardens, flowering trees/shrubs, and ornamental plants. 

High Potassium:

• Potassium helps to produce strong, sturdy plants, aids in the movement of sugar from leaves to developing fruits, and helps increase a plant’s resistance to environmental stressors. It also helps to temper acidity similarly to a liming agent, and is highly beneficial to most fruiting and flowering perennials. 

Soluble Seaweed Powder (0-0-17)

• Concentrated organic kelp powder provides over 60 nutrients and growth enhancers. It includes an extra boost of potassium for plant metabolism of sunlight and nutrients. 

• An excellent source of food for beneficial bacteria and fungi. Can be used to promote microbial growth in compost teas.

• Promotes healthy root development, increases disease resistance and accelerates leaf shoot and stem development. Can be used as a fertilizer, be added to soil blends, and/or serve as a food source for microbial growth in compost teas. 

• Soaking seeds or bulbs in seaweed powder solution just prior to planting improves germination rate, health, and vigor in the earliest stages of growth. 

• Strengthens cuttings, transplants, and bare roots when used in the ground before planting.

Langbeinite (0-0-22)

• A naturally occurring source of potassium, magnesium, and sulfur. 

• Water-soluble, meaning plants can take up the nutrients immediately! 

• Will not alter soil pH. 

• Slow-release. 

• Ideal for fruit and vegetable production in magnesium deficient soils. 

Sunflower Hull Ash (0-4-34)

• An organic source of Phosphorus (6%), Potassium (36%), and Calcium (8%), and an array of micro nutrients. 

Soil Conditioners

Amendments that are conditioners improve soil structure by increasing aeration, water holding capacity, and nutrient holding capacity. Some can correct excessively acidic or basic pH. They’re especially helpful in clay soils. 

Greensand (0-0-1.4)

• Contains iron, magnesium, silica, calcium, phosphorus and 30+ trace minerals. 

• Helps to loosen heavy, dense clay soil and can also increase water retention in sandy soil.

• Highly recommended for planting fruiting trees and shrubs.

Kelp Meal (1-0-2)

• A natural growth stimulant that can be safely used around trees, shrubs, on lawns, added into container gardens or vegetable gardens. 
• Broadcast, apply when amending soils or for transplants, or brew into kelp meal tea.
• Boosts germination, root development, and general growth. 

Garden Lime 

• Lime raises (or “sweetens”) the pH of acidic and/or clay soils. (I.e. it makes the soil pH more basic.)
• Slowly releases calcium into the soil. 
• Most effective when applied during the late autumn or early winter as it can take several months to properly correct soil acidity. Can be applied to cold, frozen, or dormant soils. 

Azomite (0-0-0.2)

• Azomite is a naturally occurring mineral product that contains over 70 active minerals and trace elements and is generally recognized as safe. Excellent for coating seeds for maximum germination and initial growth. 

“The Law of the Minimum” states that plant growth is determined by the scarcest limiting nutrient. If one of the many required nutrients is deficient, the plant will not grow and produce at its optimum. Conventional fertilizers focus on macro-nutrients such as nitrogen, Phosphorus, and Potassium. However, if one of the many essential trace elements is deficient, the plant will not produce or perform at its optimum capacity. 

Aragonite (Raw Oyster Shell Flour)

• Aragonite is made of ground oyster shells providing an ocean based source of calcium for your soil.
• Sandy texture makes it an excellent addition to clay soils. 
• Can also be added to potting and planting mixes for drainage and nutrients. 

Gypsum

• Gypsum is a type of limestone that is primarily comprised of calcium (22%) and sulfur (17%). 
• Helps to improve the structure of heavy clay soil and increases the availability of calcium in soils.
• Does not affect pH. 
• Sulfur is especially important in plants in regards to sugar content and flavor. 

Rock Phosphate (0-20-0)

• One of the best natural sources of phosphorus and calcium. 
• Should be plowed under or turned into the soil. 
• Insoluble in water which means it will not leach away and is long-lasting. 
• Can also be used directly under the seed or transplant at planting time. 
• Almost impossible to over-apply. 

Biostimulants

CharGrow Bio-Granules

• A biochar-based inoculant that contains beneficial microorganisms and microbial foods. When added to growing mediums and native soils, it has been shown to enhance biological activity and plant performance. 

Dry Molasses

• Dry Molasses quickly stimulates microbes. These microbes can offer countless benefits to your soil structure such as, but not limited to decomposing organic matter, fixing nitrogen for plant uptake, degrading pesticides, and helping control diseases. 
• May also repel fire ants. 

EndoMycorrhizal Inoculant

• This amendment contains 9 different kinds of endomycorrhizal fungi. This type of fungi not only bonds to the roots of your plants but they grow inside the roots in order to increase nutrient absorption and water efficiency. 
• Coat seeds before planting, use as a root dip when transplanting, or mix into the soil. 
• A general purpose inoculant for all types of plants. 

Fulvic Acid

• Fulvic Acid is a natural biostimulant. Biostimulants cause changes in structural processes of plants and seeds in order to influence plant growth through improving tolerance to stresses. Ultimately they improve seed yield and quality. 

Compost Kicker

• This amendment is formulated to enhance the composting process when composting mostly brown matter like wood chips and dry leaves. It contains a dry blend of nitrogen-rich materials to help boost the productivity and biological activity of compost piles. It also contains nutrients to feed microbial populations and fortify finished compost. Just lightly dust a cup of kicker to each layer of compost you add on your pile! 

	Article Written by: Hannah Gibbons
	About the Author: Hannah Gibbons, an employee at Sow True Seed since 2020, has nearly a decade of experience in the agricultural industry. Their passion for environmental education and regenerative agriculture has been the cornerstone of their work, aimed at making gardening accessible to all.