• Garden Soil Nutrients: Give Your Plants a Well-Balanced Diet

May 09, 2019

My plants don't look healthy. I've given them plenty of fertilizer, but it's not helping! If all you ate was fresh, wild-caught Copper River salmon, how do you think you'd feel after a couple months? Salmon is delicious, and it contains essential nutrients to keep us healthy, but it doesn't fit all our needs. Just as people do, plants need a variety of nutrients for healthy growth and disease resistance.

You don't have to have a degree in earth sciences to find out what minerals and nutrients your soil needs (your friends here at Seed Needs would be screwed if that were the case). All you need is a decent soil testing kit, a nearby garden supplier, and a couple bottles of wine.

Macronutrients: The Triple-Crown of Essential Plant Nutrition

Nitrogen, phosphorus, and potassium are the primary building blocks for plant health, and most plant foods will have some combination of the three. All soil nutrients work best when incorporated into the soil well before planting time, but timely applications balanced for specific growth and production stages can boost plant health.

By the way...Chlorosis is a condition that describes yellow leaves with green veins, sometimes with brown leaf edges (scorch). Chlorosis appears in this post about as many times as "the," but that's better than writing "yellow leaves with green veins, sometimes with brown leaf edges" a gazillion times.

Nitrogen (N)

This is the plant's primary "food" source and the key component for photosynthesis. It's also essential to creating plant proteins. Nitrogen doesn't just directly benefit plants—it also sustains the living ecosystems in soil and compost.

  • Signs of deficiency: Slow or stunted growth, yellow leaves, small leaves.
  • Good sources: Alfalfa pellets, blood meal, composted animal manure, cottonseed meal, feather meal, fish emulsion/meal, garden and household compost, legume cover crops, soybean meal, urea. Also, salmon...though we'd rather you sent your surplus to us. On dry ice, of course.
  • How to apply it: For emergency plant CPR, spray the leaves with a liquid nitrogen-heavy solution.

Phosphorus (P)

Plants need phosphorus to grow healthy root systems, but later on, they need it in greater quantities to produce flowers and set fruit. Phosphorus helps convert other nutrients into usable form, and it's essential for cell division and plant growth.

  • Signs of deficiency: Deformed or dropped leaves, leaf scorching, slow growth, or excessively dark green foliage.
  • Good sources: Bat guano, bone meal, compost, fish bone meal, rock phosphate,
  • How to apply it: Give your plants a phosphorous boost before flowering for best fruit or bloom production. Apply liquid solutions at soil level to avoid burning the leaves, or work bone meal into the soil around the roots prior to watering.

Potassium (K)

Also called "potash". Vibrantly-colored, flavorful fruit and veggies need lots of potassium. It's essential for the plant's ability to regulate and distribute moisture, sugar, starches, and nutrients, and aids in carbon dioxide uptake. Potassium boosts disease-resistance, promotes cell wall growth, and helps plants over winter and withstand drought. It also promotes enzyme production and adenosine triphosphate (ATP), essential to plant growth. Want delicious, gorgeous produce? You need plenty of "Special K."

  • Signs of deficiency: Chlorosis, purple spots, poor root development, stunted growth, early frost kill, desiccation, and heat intolerance: Anemic-Looking, flavorless fruits.
  • Good sources: Crushed granite/granite dust, greensand (glauconite), hardwood ashes, kelp meal, potassium sulfate, potassium chloride. Save and compost your banana peels and coffee grounds!
  • How to apply it: Work potassium-rich materials or granular food into the top eight inches of the soil before planting, or use a diluted liquid fertilizer at soil level.

Micronutrients: It's The Little Things That Count

spraying fertilizer soil nutrients directly on flowers

As they say in Hollywood, there are no small roles. These are the "secondary" soil nutrients that enhance plant growth, health, and production. Some stick around in the soil for a long time, while others might become depleted in a season or two. Either way, your soil only needs micro-nutrients in very small quantities and if you're adjusting their levels with store-bought additives, be sure not to over-do it. We recommend contacting your local agricultural extension office for the most accurate soil profiles and advice if you're troubleshooting nutrient issues at the micro level.

If all you're feeding is NPK-heavy plant food, it could tip the scales against these valuable minerals. Most of the following affect a plant's ability to absorb and "digest" nutrients from the air or soil, largely through enzyme production and cell health. Deficiencies share most of the same symptoms, which is why you'll probably get a different diagnosis for yellowed leaves if you survey different gardening sites...or weekend-warrior gardeners.

Calcium (Ca)

  • Signs of deficiency: Chlorosis, split produce, hollow fruit (typically melons and squash) growth tip and bud necrosis, poor root growth, split stems, poor shelf life, blossom end rot.
  • Good sources: Bone meal, limestone, dolomite, crushed oyster shells; all slowly release nutrients.
  • How to apply it: Work the above into the soil before planting.

Magnesium (Mg)

  • Signs of deficiency: Root shock, flavorless produce, small fruits, chlorosis. Poor nutrient uptake and foliage growth.
  • Good sources: Dolomite, limestone, magnesium sulfate (Epsom salts).
  • How to apply it: Work dolomite and lime into the soil before planting. Dissolve one tablespoon of Epsom salts per gallon of water and apply at soil level twice a month. Also good for lawns.

Sulphur (S)

  • Signs of deficiency: Chlorosis, slow or stunted growth. Depletion may increase soil acidity; sulfur is used to lower pH. Poor flower, blossoms, and fruit production.
  • Good sources: Elemental sulfur, ammonium thiosulfate solution (ATS); you'll find appropriate sulfur-based fertilizers at most garden stores.
  • How to apply it: Application depends on the type of sulfur source. Elemental sulphur needs to oxidize to be effective, and should be applied a few weeks prior to planting. ATS can damage seeds and seedlings, so it too must be applied well in advance of planting. Read packaging instructions carefully.

Boron (B)

  • Signs of deficiency: Deformed, thick, and brittle new growth; poor root growth, chlorosis in uppermost leaves.
  • Good sources: Soluble trace element mix (S.T.E.M.) at < one ounce per 25 gallons, or dissolve 1/2 teaspoon Borax in a gallon of water.
  • How to apply it: Narrow margin of error, so use caution when applying concentrated boron. Purchase an over-the-counter NPK fertilizer that includes boron, and follow the instructions carefully. Too much calcium, as well as high humidity and overwatering, can inhibit boron uptake.

Copper (Cu)

  • Signs of deficiency: Poor plant growth, and low vitamin-A levels in the produce. Bluish-green leaf tips, sterility.
  • Good sources: Copper sulfate, copper oxide, or copper chelate.
  • How to apply it: Copper remains in the soil up to eight years and accumulates. Take plant or soil samples before applying copper, and follow product instructions to the letter. Broadcast or apply to foliage.

Iron (Fe)

  • Signs of deficiency: Chlorosis, primarily on upper leaves; potential leaf whitening or deformation, stunted growth; reduce nitrogen fixation by legumes.
  • Good sources: Chelated iron (powder or granular) or iron sulfate (usually in liquid form).
  • How to apply it: Phosphorus can deplete iron, so if there's a "gap" in your soil profile, choose a phosphorous-free iron additive. Apply to foliage for immediate correction, and work solid iron additives into the soil for long-term stability.

Manganese (Mn)

  • Signs of deficiency: Reduced germination (or no germination at all), slow growth, chlorosis. Low levels inhibit access to calcium and phosphorous, so you'll see similar symptoms.
  • Good sources: Manganese sulfate; dolomite (dolomitic limestone).
  • How to apply it: Both sources are best applied to the soil before planting. Base your application on soil tests or product packaging. Spread on the soil surface, and work it in six to eight inches deep.

Molybdenum (Mo)

  • Signs of deficiency: Chlorosis on upper leaves, poor nitrogen fixation, especially in legume plants. Stunted plant and root nodule growth.
  • Good sources: Compost or liquid NPK solutions with trace amounts. Buy coated, inoculated legume seeds or use Rhizobium additives that contain molybdenum.  
  • How to apply it: As a legume seed coating, or evenly added to beds before cultivating. Foliar spray in emergencies. Rarely a problem due to the extremely low levels required. Difficult to diagnose in typical soil test kits. Potential issue when sulfate levels are high. High-quality compost and, for large legume crops, inoculated seeds should eliminate the risk.

Nickel (Ni)

  • Signs of deficiency: Low germination rates in seeds from deficient plants (DEFINITELY not our seeds!). Reduced microbial life in the soil. Stunted growth. Chlorosis in new leaves. Sudden seedling failure and reduced crop production.
  • Good sources: If your soil test reveals a nickel deficiency, choose a fertilizer that has trace amounts of Ni. Otherwise, count on quality compost to correct the issues.
  • How to apply it: Too much nickel can counteract other essential nutrients. Water with excess metals may be the cause. Never add nickel if the levels are normal or above normal.

Zinc (Zn)

  • Signs of deficiency: Low yields, and—you guessed it—chlorosis, which first appears on a plant's lower leaves where they meet the stem.
  • Good sources: Typically replenished with quality compost, but zinc chelate or kelp will greatly improve the soil.
  • How to apply it: There's a wide margin of error on the "overdose" end of the spectrum. Kelp, either added around the roots or diluted for a foliar spray, will hold over sick plants until the soil amendment kicks in. Zinc can last in the soil for about five years, accumulating in the meantime, so test before re-applying.

Thoughts on Manure and Additives: Know Your Sh*t!

Just because something sounds organic doesn't mean it is. Some livestock hay and concentrated rations—including alfalfa pellets and meal—contain aminopyralid herbicides that pass through the animal's digestive system and into the manure. You can easily find organic alfalfa pellets, but if you're raiding a stable or farm's "free manure" pile, you'll sound like a choosy beggar if you ask, "Hey, do you feed your animals 100% organic fodder?" Most horse, cattle, sheep, rabbits, and goat owners won't even know, because they probably outsource their hay anyplace they can...and due to invasive noxious weeds, the "best" hay comes from routinely-sprayed fields.

Have you ever heard of straw bale gardening? We have a couple of customers whose gardens spectacularly failed because they purchased straw cut from herbicide-laden grain crops. Chicken manure often contains nest and floor litter straw, and horse owners use straw in stall bedding.

Cotton is one of the highest-input crops, and cottonseed meal may have residual pesticides and herbicides. So might soybean meal.

If you can make your own compost and monitor what goes into it, you're far better off. We also suggest you check with your local 4-H clubs or FFA chapters to connect with (and support!) young livestock keepers who use organic feed. They may even talk you into buying some chickens, goats, and bunnies so you can have your own backyard poop factory.

Optimize Your Compost's Nutrients for More Nutritious Food

Just like with soil, compost can suffer from nutrient imbalances—especially if you only use it to dispose of lawn clippings and dead leaves. If you have a composting system at home, feed it with as wide a variety of greens and browns (nitrogen and carbon materials) as possible. If you're going the store-bought or landscape supply route, mix at least two types or brands of compost before digging it into the soil.

Your soil and compost quality affects your garden produce's nutritional value and flavor. That's at least half the battle. When you plant heirloom seeds bred for quality rather than for shippability and shelf life, and grow them in microbe-rich, well-balanced beds, you can count harvesting backyard garden produce with the absolute best taste, texture, vitamins, and minerals.

We'll Supply Your Seed Needs, But Your Dirt's on You

We wish we could ship you bags of fertilizer and soil amendments, but our focus is sourcing and selling open-pollinated seeds from healthy parent stock. We're a small family operation, and hey... Mom wouldn't be too cool with having stacks of steer manure in the living room, and a certain member of the family is on "a list" and can't have access to large quantities of certain bomb-making ingredients. (Kidding! But now we're on a list for writing that!)

Do you have before-and-after garden photos? Want to tell us how you've improvised with your garden nutrients? Contact us! We'd love to hear from you, whether you want to share your successes, ask for help, or offer feedback. You can even give us crap if you have a problem with your order, and we'll work hard to make things right.


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