Soil Amendment

Soil amendment for the health of your garden using these three nutrients

soil amendment

If you want to ensure the longevity of your garden beds, soil amendment is crucial. Ideally, if you’re keeping up with cover cropping and crop rotation you won’t need to do soil amendment too often. However, it is inevitable! Some common reasons to amend your soil are:

  • You’ve tested your soil pH and it’s come back extremely acidic or basic (recommended pH 6.5-7.3),
  • You’re experiencing vegetable diseases and/or lack of fruiting,
  • You’re looking for materials that will enhance aeration,  structure, & moisture retention, or
  • You desire a healthier environment for beneficial insects to thrive.

When do I amend my soil?

Regardless of whether you’re amending existing or new beds, a general rule of thumb is to add ⅓ material to your existing ⅔ topsoil. The best times for soil amendment are a week prior to seeding, ie: before your spring planting (January/February) and before your autumn planting (August/September).

How much amendment do I add?

Please keep in mind that adding MORE amendment than necessary does NOT mean your soil will be better off. Adding the recommended doses of soil amendment is crucial to a balanced soil ecosystem.

Top three nutrients to amend your soil

The top three nutrients to amend your soil are Nitrogen (N), Phosphorus (P), and Potassium (K). These minerals are the most heavily used by plants and thus, will most commonly be depleted from your soil.

Soil Amendment

#1- Nitrogen (N):

Nitrogen is a nutrient that promotes strong stem and leaf growth, as well as the production of amino acids and proteins. Some examples of soil amendments that are high in Nitrogen include:

  • Fish emulsion
  • Mulch & aged bark
  • Cottonseed
  • Seabird guano
  • Feather meal
  • Blood meal
  • Alfalfa meal
  • Cover crops such as rye grass, oats, and beans

*Note: It’s recommended to not over fertilize with Nitrogen soil amendments going into the winter as low light and cool soil temperatures decrease Nitrogen uptake.

Soil Amendment


#2- Phosphorus (P):

Phosphorus is a nutrient that promotes flower, fruit, & root growth. It is also beneficial to help with disease resistance. Some examples of amendments that are high in Phosphorus include:

  • Ground rock phosphate
  • Fish emulsion
  • Kelp
  • Happy Frog
  • Bat guano
  • Bone meal

#3- Potassium (K):

Soil Amendment

Potassium is a nutrient that promotes the overall health of a plant. It also helps regulate water retention and aeration within the soil ecosystem. Some examples of amendments that are high in Potassium include:

  • Kelp
  • Seaweed
  • Fermented banana peel and water spray
  • Wood ashes
  • Coffee grounds
  • Bat guano

Soil amendments for air and moisture balance:

  • Vermicompost (provides moisture retention and has a complete nutrition composition)
  • Organic Cotton Burr or Cotton Boll (is a soil conditioner and provides aeration & disease prevention)
  • Perlite (provides moisture retention and proper drainage)
  • Compost (provides moisture retention and has a complete nutrition composition)
  • Coconut coir (helps with moisture retention)

Soil amendments for pH balance:

  • Raise pH: oyster shells, lime, diatomite rock
  • Lower pH: sulfur

Soil amendments for an overall nutrient boost:

  • Biochar (is also high in carbon)
  • Egg shells
  • Azomite
  • Alfalfa meal (is also a compost catalyst)


Desiree RoseDesiree Rose is a gardener, content developer, artist, and embodiment coach. With a degree in Resiliency Leadership and Environmental Education, she’s had the opportunity to study intensively under many thought-leaders in the fields of Environmental Agroforestry, Women’s Embodiment, Ayurveda, Astrology, Life-Coaching, Curriculum Design, and Biodynamic Beekeeping. When she’s not tending the gardens at Growing Spaces, she can be found rock climbing, highlining, and soaking in the hot springs in southwest Colorado.

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