Chemistry of Gardening: What nutrients do plants need?

ChemistryOfGardeningIf I ask my four year old what it takes for a plant to grow she can quickly respond with response, “Sun, water, air, and soil”  This is a great answer for photosynthesis since plants need energy from the sun.  They leverage the carbon dioxide (CO2) from the air and water (H2O) to create starches and sugar.  Now the soil part of this answer is where things get a little more complicated.  Soil gives plants the ability for roots to expand and grow but also provides many nutrients to help them as well.

Similar to humans, plants need various minerals to live healthy lives.  The primary macronutrients Nitrogen (N), Phosphorus (P), Potassium (K) are required to sustain life.  These are the nutrients that plants consume significant amounts which is why these are advertised in big letters on the outside of packages of fertilizer.


Nutrients Benefits Signs of Deficiency Sources (N-P-K)
Nitrogen (N) Provides energy to allow vegetative growth.  Leafy plants can’t get enough, root plants need very little, fruiting plants need plenty in beginning but too much later in growth cycle will result in big/tall fruitless plants. Light green to yellow leaves; growth stunted Bloodmeal (14-0-0)
Alfalfa meal (7-3-4)
Soybean meal (6-1-2)
Cottonseed meal (6-2-2)
Fish emulsion (5-2-2)
Chicken Manure (3-4-3)
Compost (1-1-1)
Cow Manure (.2-.2-.2)
Phosphorus (P) Makes plants more stress resistant, allows for fast growth, encourages bloom and root growth. Red or Purple leaves; cell division slowed Bonemeal (4-12-0)
Chicken Manure (3-4-3)
Alfalfa meal (7-3-4)
Compost (1-1-1)
Potassium (K) Helps with photosynthesis process, immunities to disease, and increased quality of fruit. Vigor reduced; susceptible to disease; thin skin; small fruits Alfalfa meal (7-3-4)
Greensand (0-0-3)
Wood ash (0-1-3)
Chicken Manure (3-4-3)
Compost (1-1-1)

We could live off a simple food like gummy bears for quite a while, but our quality life will decrease once we picked up scurvy and exhibit significant bone and muscle loss.  The same idea goes for plants, they can live simply on the primary macronutrients but they will live poor and possibly fruitless (literally) lives.  This is where the secondary nutrients come in.  With the exception of Calcium, these are not consumed in nearly the volumes as the primary macronutrients though supplementation may be required.


Nutrients Benefits Signs of Deficiency Sources
Calcium (Ca)

Helps with cell wall structure imperative for strength of plants

Growing points of plants damaged Dolomitic limestone, gypsum, egg shells, antacids
Magnesium (Mg) Required as part of the chlorophyll required for photosynthesis Yield down; old leaves white or yellow Epsom salt, Dolomitic limestone, organic material
Sulfur (S) Required for to allow plants to create protein, enzymes, and vitamins.  Helps with seed, root growth, and resistance to cold. Light green to yellow leaves; growth stunted Rainwater, gypsum

Finally are the macronutrients, these are the nutrients that most of the time, as long as you are not growing with hydroponics. should exist in your soil and rarely need to be supplemented due to the small amounts that are consumed by plants, nevertheless are still very important for plant growth.


Nutrients Benefits Signs of Deficiency Sources
Boron (B) Helps in production of sugar and carbohydrate
s.  Essential for seed and fruit development.
Small leaves; heart rot (corkiness); multiple buds Organic Matter and borax
Copper (Cu) Helps in plant reproduction Multiple buds; gum pockets Copper sulfate, neutral copper
Chloride (Cl) Helps with plant metabolism None known Tap water
Iron (Fe) Helps in formation of chlorophyll Yellow leaves; veins remain green Iron sulfate, iron chelate
Manganese (Mn) Helps in breakdown of carbohydrates and nitrogen Leaves mottled with yellow and white; growth stunted Manganese sulfate, compost
Molybdenum (Mo) Helps in breakdown of nitrogen Varied symptoms Sodium molybdate, compost
Zinc (Zn) Regulates growth and consumption of sugars by the plant Small, thin, and yellow leaves, low yield zinc oxide, zinc sulfate, zinc chelate

Nutrient Deficiency Information from “The Vegetable Gardener’s Bible”

Now you are armed with plenty of information, though unfortunately you can not act on any of this without knowing the chemical composition of your soil.  If you simply went by the signs of deficiency (for example yellow leaves) could be caused by one or many nutrient deficiencies.  Fortunately you can get this information to act on by running a soil test on your soil.  There are a couple options for this if you are simply concerned about primary macronutrients there are cheap DIY home tests, electronic testers, or you can send a sample to a soil lab to give primary/secondary macronutrient and micronutrient levels and recommendations to get your soil back on track.  You may also want to check with your local municipal office they may have a cheaper/free option available to you.

Just remember, your perceived lack of a green thumb my have nothing to do with your ability but the chemistry of soil you are working with.

21 Responses to “Chemistry of Gardening: What nutrients do plants need?”

  1. Tatyana Says:

    Very educative post, thanks! And I am impressed by your son’s knowledge in this area!

  2. Mark Says:

    For some insights on photosynthesis, your readers can go to Photosynthesis Process.

  3. Matt Says:

    This is going to help me on my science fair project, thanks!

  4. Matt Says:

    This is going to help me on my science fair project, thanks!

  5. Compostings Says:

    What a great post! Thanks for the detail.

  6. Anonymous Says:

    Now I know why my pumpkins died…

  7. The Cheap Vegetable Gardener Says:

    Tatyana, well technically my daughter’s knowledge, glad you enjoyed it.Mark, thanks for the infoMatt, will be checking your blog for more info on your science fair project, good luck.Compostings, glad you enjoyed it, I learned quite a bit writing it.Anonymous, what were your pumpkins they missing?

  8. Amy Says:

    if you add rice bran to water, and use that to water the plant would it help it grow faster? rice bran is one of the foods highest in phosphorus.

  9. Anonymous Says:

    Wow this will be great for my science project and it is interesting. Maybe this will help my brown thumb

  10. Rex Says:

    The links do not work on my PC – Windows XP

  11. The Cheap Vegetable Gardener Says:

    Links should be fixed now, thanks for the heads up

  12. Magnolia Says:

    This is great information. I am trying to educate myself in this area so I can start up and indoor farming operation. Aeroponics is how I’d like to grow and there are nutrient mixes available, but I’d like to better understand how to determine what my plants are lacking and how to fix it!

  13. Shana Says:

    Hi i was wondering what the numbers mean beside each of the ingridents, i how its the amount for N P and K but is it the percentage? like (3-4-3) does it mean 3 percent nitrogen is provided?

  14. Faran Says:

    this was very helpful

  15. polomint Says:

    brill, thanks for the post that has cleared loads up for me.Again thanks

  16. Joy Says:

    This helps loads for me. I have a question about what is your citation so that I can use it for my science project.

  17. Tom Says:

    Yeah this is really use full for plant related science projects. Thanks alot!

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