Plant Nutrients

Plants need more than just soil, moisture, and sunlight to thrive. They also need nutrients, especially if they're planted in a pot or bed, since the nutrients can leach out the bottom over time. It's always wise to start your plants off right by adding compost, aged manure, or leaf mold to the soil before planting. These materials will slowly feed your plants over the growing season, while also increasing the beneficial organism population and build soil structure, allowing for better moisture retention, drainage, and airflow. Compost is great, but oftentimes, your plants need more nutrients at a given time. This is where fertilizers come in handy.

Organic fertilizers are always a great option, as it is a natural way to feed your plants without risk of burning them or creating nutrient run-off. Organic fertilizers slowly feed your plants over time and improve soil structure and drainage. Fertilizers may contain macronutrients and micronutrients, depending on the type of fertilizer used.

Macronutrients are the essential nutrients needed in fairly large quantities. These macronutrients are essential for plants to perform a multitude of functions, however some main functions each of the three macronutrients provide for plants are listed below.

Macronutrients' Main Functions:

• Nitrogen (N) - Chlorophyll synthesis or leafy growth (too much late in the season can cause leaf bloom, but no fruit), increases protein content
• Phosphorus (P) - Root growth and fruiting, as well as cell development and early seedling growth
• Potassium (K) - Supports disease resistance and hardiness, as well as water transport and crop yield, reduces water loss

You will often find the macronutrients listed as the N-P-K ratio on fertilizers in the garden center, so you can know how much of each macronutrient you're adding to your soil.

Organic fertilizers (with typical NPK ratios*) include: 
❀ Nitrogen (N):
        ▻ Blood meal (12-0-0)
        ▻ Feather meal (12-0-0)
        ▻ Manure
               ▹ cow (3-2-1)
               ▹ horse (0.5-0.2-0.6)
               ▹ goat (ranges: 0.7-0.3-0.5 to 1.1-0.5-0.8)
               ▹sheep (ranges: 0.7-0.3-0.5 to 1.2-0.5-0.9)
               ▹rabbit (2.4-1.4-0.6)
        ▻ Aged chicken manure (ranges: 3-2.5-1.5 to 6-4-3)
        ▻ Fish meal (10-5-0)
❀ Phosphorus (P):
        ▻ Bone meal (3-15-0) plus calcium
❀ Potassium (K):
        ▻ Alfalfa meal (2.5-0-2.5)
        ▻ Wood Ash (ranges: 0-1-3 to 0-1-2) (alkaline, so used to treat acidic soil)
        ▻ Kelp meal (1-0-2)

Compost options (with variable NPK ratios) include:
 ▻ Compost (ranges: 0.5-0.5-0.5 to 1-1-1)
 ▻ Vermicompost (ranges: 1-0-0 to 5-5-3)
 ▻ Worm tea (varies 1-1-1)
 ▻ Leaf mold (ranges: 0.5-0.5-0.5 to 1-1-1)
 ▻ Mushroom compost (varies 1-1-1)

*The NPK ratios listed here are typical for these products, but may differ from actual products available

Micronutrients are also required, but in smaller quantities than macronutrients. Sometimes, these micronutrients are already readily available in the soil and you don't have to add extra.

Micronutrients' Main Functions:

• Boron (B) - Cell wall formation & stability, membrane structure & function, transport of sugar, and pollination & seed set
• Second most commonly deficient micronutrient
• Calcium (Ca) - Balance organic acids within the plant, cell wall formation, leaf and root growth, increasing microbial activity, and nutrient uptake
• Chlorine (Cl) - Stomatal regulation and osmotic adjustments (minimizing water loss during hot, dry periods), nutrient transport
• Taken in as Chloride (Cl-)
• Copper (Cu) - Activates enzymes and catalyzes reactions, helps with chlorophyll and seed production, and aides in Vitamin A production
• Iron (Fe) - Energy transfer, nitrogen reduction & fixation, and lignin (plant cell wall) formation, carries oxygen to the roots
• Magnesium (Mg) - Respiration, photosynthesis, and carries phosphate (helping with root formation and increasing nutrient & water uptake)
• Source: Dolomitic limestone (provides Ca and Mg and neutralizes soil acidity)
• Manganese (Mn) - Accelerates germination and growth, builds chlorophyll, increases availability of P and Ca 
• Sulfur (S) - Synthesizes certain amino acids (cysteine and methionine) as well as proteins, formation of chlorophyll, photosynthesis and winter hardiness, seed production, and nitrogen fixation in legumes
• Zinc (Zn) - Increases yield, protein synthesis, growth regulation
• First most commonly deficient micronutrient

Rarely Deficient Micronutrients:

• Molybdenum (Mo) - Nitrogen metabolism and symbiotic N fixation of Rizobium in legumes
• Rarely deficient; toxic in excess (especially to grazing animals)
• Nickel (Ni) - helps urease catalyze urea (H2NCONH2) to ammonium ion (NH4+) which plants use as a source of nitrogen

Non-Fertilizer Nutrients:

• Hydrogen (H) - Plant respiration and photosynthesis, building energy, structure
• Carbon (C) - Used as energy to build carbohydrates, cellulose, lignin, protein, and starches
• Adding dead plant matter and animal waste† to your compost heap provide carbon to your compost, balancing out your compost pile
• Oxygen (O) - Cellular respiration, photosynthesis, and energy
• Only a small amount of oxygen is stored and used by plants, the rest is released as a byproduct (and then animals breathe it in :)

†Be cautious of the animal waste you choose to add to your compost pile, as some animal waste has more pathogens than others (good options include herbivorous animal waste)

Source: https://www.cropnutrition.com/crop-nutrition/key-nutrients/

How to know if your plant is deficient?

You can always test your soil to find out a lot of information about the makeup of your soil. It's wise to do this at the start of every season, just so you know what your soil lacks and what your soil already has plenty of. If you choose not to test your soil, you can give your plants a well-balanced organic fertilizer for the specific needs of your plant, as well as providing plenty of compost. Watch your plants for signs of distress. They may not be able to speak, but they do show signs when they're unhappy. Unfortunately, plants can show similar symptoms for a wide range of issues, so you need to use some investigative skills to figure out how to help your plant.

Montana State University has a great flow chart to help figure out what nutrients your plant is lacking.

Source: https://landresources.montana.edu/soilfertility/nutrientdeficiency.html

Mobile vs Immobile Nutrients:

Mobile nutrients freely move throughout the plant and go to the newer, younger leaves. If your plant is deficient in mobile nutrients, the younger leaves will appear healthy and the older leaves will appear discolored, curled, unhealthy, or fall off.
    Mobile Nutrients: Cl, K, Mg, Mo, N, P

Immobile nutrients remain where they are and cannot move to the newer growth. If your plant is deficient in immobile nutrients, the older leaves will appear healthy and the newer leaves will appear discolored, curled, unhealthy, or fall off.
    Immobile Nutrients: B, Ca, Cu, Fe, Mn, S, Zn

Updates on how to apply micronutrients coming soon.

Dirt vs Soil

Let's talk dirt!

Dirt is dead - it's not at all what you want to grow your plants in. Don't misunderstand, I'm not promoting commercial potting mixes or bagged soil you purchase in garden centers. You can certainly use natural "dirt" from the ground or what you have on hand (even old, dry, used potting mix left and forgotten from previous seasons). However, the difference between dirt and soil: life. 

Dirt is dead, devoid of all beneficial organisms (both macro and micro). There is no life in dirt, rendering it useless as a growing medium for your plants. Soil, on the other hand, is filled with beneficial organisms. This may include worms, earwigs, rolly polies, centipedes, fungus, springtails, and many more macroorganisms, or this may include microorganisms such as mycorrhizal fungi and nitrogen-fixing bacteria. 

How can I tell if I have dirt or soil in my garden/planter?
If you look closely at your medium and dig a little bit, you may find some beetles, earwigs, or other soil creatures if you're working with soil. If you notice your medium is dry, hard, caked, or otherwise devoid of moisture, it's likely dirt at this point and cannot support life - including your beloved plant. 

How can I use dirt if it's useless to support life?
    If what you're working with is dirt (dry, devoid of life), there's still hope! You don't have to toss it and purchase new soil from a garden center (though, you can certainly purchase more soil and/or compost if you don't have enough already). 
    You can bring life back in to the old dirt you have on hand, starting with rehydrating the medium. Oftentimes, it's difficult to rehydrate old potting mix, since it's often made with peat (learn why conscientious gardeners are avoiding peat products, coming soon), which is great at holding on to moisture when it remains damp, but when it dries out, it's very difficult to rehydrate without a good, thorough mixing and soaking. 
    Once you've rehydrated your dirt, you can start adding amendments to it, such as compost, vermicompost (worm castings), manure, leaf mold, bio-char, coconut coir, gypsum, vermiculite, perlite, lime, sulfur, or potash, among others. (We'll go into more detail about all these soil amendments in another article.) Depending on your plant's needs will determine which amendments you want to mix in, however for all plants, compost and vermicompost are always good options. Depending on if your plant needs a lot of nutrients or prefers a more nutrient-deprived medium will determine how much compost and other nutrient-rich components you want to add. 
    Using compost or vermicompost are great options to inoculate your dirt with beneficial microorganisms (and possibly macroorganisms) as well. By transferring and mixing in healthy compost, you're introducing all the organisms that have been breaking down the organic matter into your newly-revitalized medium and creating a living environment in which your plants can thrive. The compost also does a great job of slowly releasing nutrients to your plants over time. You may want to add some organic fertilizers, such as blood meal, bone meal, or kelp meal, to your medium as well (more about these and other organic fertilizers) to encourage healthy plant growth.

And voila! You just recycled/repurposed/revitalized (whatever term you want to throw in there) your dead dirt into living, life-giving soil, saving you money and waste, and allowing you to grow new plants in your newly-restored soil medium.

If you don't want to revitalize your old potting mix, don't throw it in the trash (unless you had pests or diseases infiltrate it). If it was just used and dry with no concerns about harmful organisms, go ahead and compost it - it'll get processed by the organisms in your compost heap and be ready to feed your plants next season.