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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.

MACRONUTRIENTS – PRIMARY

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.

MACRONUTRIENTS – SECONDARY

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.

MICRONUTRIENTS

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.

Teaching children patience with gardening

It shouldn’t be a surprise that kids these days are not as patient as previous generations.  Personally I feel this is less on a change of parenting but a result of children’s expectations created because of the advance of technology.  For example, When my daughter asks to watch a particular show “On Demand” and then 5 minutes later asks me to “pause it” so she can go potty.  This makes me think back to the days of having a single TV station we could pick up with our antenna, which seemed to play reruns of MASH 24/7.

The great thing about gardening is with the exception of seed hybridization, synthetic fertilizers, and maybe techniques like hydroponics the hobby hasn’t changed too much in the past few hundred years.  It still takes 1-3 weeks for seeds to germinate not matter what technology you throw at them.  This is why I feel gardening is a great activity to share with the young ones in your life to help offset the instant gratification they see on a daily basis.

Here are a couple of ideas how to do this any time of year:

Cup of Dirt: Give your young one a cup of dirt and some seeds.  To keep them interested give them a spray bottle to water everyday to keep them coming back every day to check how their plant is doing.  The spray bottle will provide just enough water on the surface to allow the seeds to germinate and what kid doesn’t like to play with a spray bottle.

Sprouting in a Jar: I have a complete post on this topic, but the process is pretty simple.  Get a mason jar and add some seeds.  Rinse, drain and repeat.  In just a few weeks you will have tasty and healthy sprouts you can add to your salads, sandwiches, stir-frys, etc.

Growing plants in water:  Now this can be as complicated as setting up a hydroponic environment or as simple as taking a spider plant start and placing it in some water and letting your young one watch as the roots develop and transplant and care for it as a new plant.

My Lettuce seeds have sprouted


My lettuce seeds sprouted faster than usual this year, I expected to have some problems since I have saved the seeds for 3 years now. I don’t have a heating pad (yeah I’m cheap) so just put them on top of the refrigerator in a makeshift greenhouse out of an old strawberry container. They would have still germinated in my mid-60 degree house, but the extra heat gained from being on top of the refrigerator will allow my cucumbers to sprout about 10 days sooner.

I will have to give coconut coir my two green thumbs up, my only complaint is that it retains water a little too well. I would recommend 1 part perlite to 2 parts coconut coir to let the roots dry out a little more. For now I am just watering from the bottom so guess I am doing some cheap hydroponics. I have also added them to my PC case grow box.

Science Fair: Why don’t strawberries grow during the wintertime?


My 6 year old daughter was the inspiration for the PC grow box for her science fair project to figure out why strawberries don’t grow during the wintertime. She started by picking a strawberry plant from our garden (snow still on the ground) and we potted it in a terra cotta pot which she carefully painted ahead of time. We put it in the grow box in our garage with the lights on for 14 hours a day. As she saw significant changes in her strawberry plant we took pictures. After about a month of growing we went through the pictures and she wrote her report explaining the changes.

She definitely had a good time standing by her display proudly telling people about her project and answering any questions that the various visitors had. She did take a break to take a look at some of the other kids displays which I took note of the gardening related ones which would be great for a science projects for any of your budding scientists:

– Seed germination (soil or paper towel)
– How plants grow with different color of lights (colored transparent plastic)
– How plants grow when given different liquids (water, soda, milk, vinager, diet soda)
– Effects of being mean or nice to plants
– Effects of music on plant growth
– Hydroponics
– Effects of temperature on plant growth

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