Plant Nutrition

Plant nutrition involves 13 essential minerals: three macronutrients, three secondary nutrients, and seven micronutrients (formerly known as “trace elements”). While needed in smaller quantities, the micronutrients are still essential to plant life.

The Thirteen Essential Plant Nutrients

Macronutrients

  • Nitrogen (N)
    Needed for chlorophyll and protein production, and used in general plant growth
  • Phosphorus (P)
    Needed for photosynthesis (specifically, converting light energy into chemical energy), strong stems, making blooms and root growth
  • Potassium (K)
    Needed for photosynthesis, production of proteins, starches and sugars, fruit production, and disease resistance

Secondary Nutrients

  • Calcium (Ca)
    Component of cell walls, needed for uptake and utilization of other minerals
  • Magnesium (Mg)
    The central atom of a chlorophyll molecule, needed for enzyme activity 
  • Sulfur (S) 
    Needed for protein, enzymes, chlorophyll, vitamins, roots and seeds, and more!

Micronutrients

  • Boron (B)
    Kind of a “Master Nutrient” that helps all the other nutrients be utilized, needed for stalk strength, seed and fruit development, carbohydrate formation
  • Chloride (Cl)
    Needed for metabolism
  • Copper (Cu)
    Needed for root growth and protein metabolism, seed production
  • Iron (Fe)
    Necessary for the production of chlorophyll
  • Manganese (Mn)
    Needed by enzymes for metabolism
  • Molybdenum (Mo)
    Needed for nitrogen metabolism
  • Zinc (Zn)
    Needed for plant growth

Organic Fertilizers

There are a number of organic fertilizers that can be used to supply these nutrients in an organic vegetable garden. The table below lists only the "N-P-K" values. To supply virtually all the micronutrients, use kelp meal. 

For instructions on how to calculate how much of which organic fertilizer may be needed in your garden, see the soil sample and organic fertilizer articles.

Organic Fertilizer Chart

Fertilizer About
Nitrogen
Phosphorus
Potassium
Alfalfa meal alfalfa is a high-nitrogen plant
2
1
2
Bat guano bat poop mined from the floor of caves
4
5
2
Bone meal (raw) from animal bones
4
12
0
Bone meal (steamed) from animal bones
1
13
0
Blood meal dried blood from slaughterhouses
13
0
0
Cottonseed meal*** from cotton seeds
5
2
1
Feather meal from chicken slaughterhouses
12
0
0
Fish meal from fish canneries
10
6
2
Greensand mined from the ocean floor
0
0
3
Kelp meal dried seaweed
1
0
1
Phosphate rock mined sedimentary rock
0
5
0
Soy meal ground soybeans
7
2
1
*** Cotton is not a food crop and so usually contains nasty pesticide residues. Use only organically-grown cottonseed meal.

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