Understanding Plant Nutrition Shopping for fertilizers in Salt Lake City isn’t always easy. Gardeners understand that fertilizers — and healthy soil in general — are essential for plant growth. But how do you decide which ones your plants need the most? Allow us to guide you in this process.

Plants need 19 elements to achieve optimal growth. These include oxygen, carbon and hydrogen, which are primarily supplied by air and water. The remaining 16 elements are absorbed by plants from the surrounding soil and divided into three groups in order of their relative abundance in plants:

  • Primary/Major Nutrients — Great quantities are essential for plant growth; a deficiency stunts growth.
  • Secondary/Minor Nutrients — These are essential for healthy plant growth.
  • Trace Nutrients/Micronutrients — These increase chances of healthy plant growth.

Some soils already have these nutrients, but they may not be in the form plant growth requires. To make sure your garden soil has all these elements before planting, you must regularly apply the required amount of plant food.

Plant Nutrition

The table below provides more information on each nutrient, its deficiency symptoms, and possible plant foods to cure the deficiency.

Primary NutrientsFunctionDeficiency Symptoms*Solutions
NitrogenVigorous growth & dark green colorLight green leaves; stunted growthDried Blood, Garden
Manure, Cottonseed Meal, Urea
PhosporusRoot development & floweringSmaller yields of seeds &
fruit; purplish leaves, stems & branches;
Rock Phosphate, Bone
Meal, Single Super
Phosphate, Triple Super
PotassiumOverall hardiness & disease resistanceReduced yields; Spotted or curled leaves; Weak root systemMuriate of Potash, Greensand
Secondary NutrientsFunctionDeficiency Symptoms*Solutions
CalciumPlant vigor; Aids in uptake of nutrientsDeformed terminal leaves; Poor root growthGarden Lime, Garden Gypsum
MagnesiumEssential part of chlorophyllYellowing of older leavesGarden Lime
SulfurDark green color; Seed productionYellow leaves; Stunted, spindly plantsGarden Sulfur, Gypsum
Trace NutrientsFunctionDeficiency Symptoms
BoronIncreases flowering & fruit developmentTerminal buds die; Less flowers & fruit developGarden Manure, Bone Meal
ChlorineHelps control water loss & moisture stressPlants wilt; yellow leavesGarden Manure, Greensand
CobaltImproves growth & transpirationReduced growth and
yellowing of foliage
Greensand, Kelp, Cottonseed Meal
CopperHelps produce chlorophyllYellow, wilted leaves; Lack of floweringGarden Manure, Greensand
IronPromotes dark green leavesYellow leavesGreensand, Garden Manure, Cottonseed Meal
ManganeseHelps produce chlorophyllIntravenous chlorosis in younger leavesGarden Manure, Greensand
MolybdenumEssential in some enzyme systemsPale green, rolled or cupped leavesGreensand, Lime (makes it more available)
NickelEnzyme ProductionYellow LeavesGreensand
SodiumAids water regulation & photosynthesisPlants wiltKelp, Garden Manure, Bone Meal, Greensand
ZincEnzyme & growth hormone productionYellow leaves, Rosetted (clustered) leavesGarden Manure, Greensand, Cottonseed Meal

Comparing Labels

Not all commercial plant food items are created equally. Learn to read plant food labels — this can help you distinguish among seemingly similar products.

1.Guaranteed Analysis — This represents the percentage of nutrients by weight the seller claims. If the manufacturer claims a given nutrient, it must be guaranteed in this section.

2.Grade – This is a shorthand representation of the minimum percentages guaranteed (by weight) for total nitrogen, available phosphate and soluble potash, with each guarantee separated by a hyphen. In Figure 2, the grade for Plant-tone is 5-3-3, which means that it is guaranteed to contain 5% nitrogen, 3% phosphate and 3% potash. So in a 40 lb. bag of Plant-tone, there would be 2 pounds of nitrogen, 1.2 pounds of available phosphate, and 1.2 pounds of soluble potash.

3.Net Weight — Most plant food items are sold by net weight rather than volume. But when comparing fertilizer costs, it’s better to look at the price per pound, as net weights often vary.

4.Derivation Statement — This enumerates the sources of nutrients guaranteed by the manufacturer. Keep in mind that the more nutrients each package contains and the more rates of release, the better the feed. When it comes to fertilizers, it’s better to opt for slow-release varieties.

Tips for Comparing Grades

Keep in mind that plants can’t use nutrients immediately. Excess plant food leaches away from the soil. This is why slow-release varieties (natural, organic or controlled) are better because they slowly feed the plant as it grows.

Some labels represent the percentage by weight of a given nutrient, but others don’t.

In the comparison table below, you can see that Espoma Organic provides more nitrogen per 1,000 square feet than two competitor products; one with a higher nitrogen analysis and another with a lower nitrogen analysis. This is an example of how bigger doesn’t always mean better when you take weight and rate into consideration.

BrandAnalysisApplication Rate
per 1,000 sq. ft.
Nitrogen per
1,000 sq. ft.
Espoma Organic7-2-212 lbs.0.84 lbs.
Espoma Lawn Food18-0-34 lbs.0.72 lbs.
Brand X (Natural)3-1-510 lbs.0.3 lbs.
Brand Z (Synthetic)16-4-84 lbs.0.64 lbs.

You’re probably wondering, is there any slow-release nitrogen?

Yes. To identify how much nitrogen is slow release, add the percentage of “water insoluble” nitrogen to any other “slowly available” nitrogen in the guaranteed analysis. In the Plant-tone label above, 3% nitrogen (approximately 60% of the nitrogen guaranteed) is slow release. In the X and Z brand labels, there is no water insoluble guarantee or any other slow-release claim. So this is a water-soluble product that will not last long in the soil.


Choosing the Right Fertilizers

Fertilizers generally fall into two categories, namely synthetic and natural organic plant food, each with its own merits and drawbacks.

Synthetic Plant Food

The obvious disadvantage of this type of plant food is that it contains ingredients manufactured chemically, but it can help solve some problems in the garden. There are two types of synthetic fertilizers:

  • Water Soluble — This type of fertilizer dissolves in water and releases nutrients instantly. It’s ideal in nurseries with drip irrigation. Since feeding can be rapid and short-lived, this would require frequent applications and a good plant food-to-water ratio. Leaching can be a problem in sandy soils or high-moisture conditions. And due to the high solubility and salt index, burn or dehydration potential is also higher, so take extra measures when using this product in nurseries or greenhouses. Some water-soluble plant food items include ammonium sulfate, ammonium phosphate and urea.
  • Controlled Release — This type of plant food releases nutrients much more slowly than water-soluble varieties. Two mechanisms delay plant uptake. One, water-soluble plant food, like urea, is coated with wax, plastic or molten sulfur. The thicker the layer, the slower the feeding. Two, materials are combined to form insoluble polymers to deliver long-lasting feeding. While both forms provide nutrients to the soil, neither contains all the advantages of natural organics.

Natural Organic Plant Food

These are nontoxic fertilizers made from natural sources such as plant, animal and mineral products that contain one or more essential nutrients for good garden soil. Some examples include cottonseed meal, bone or blood meal, kelp meal, manure, greensand and fish emulsion. While all fertilizers feed nutrients to plants in a chemical form, organic derivatives release nutrients more slowly without aiding mechanisms, making them the superior choice.

Healthy Soil Makes Healthy Plants

The key to a lush and prolific garden is great soil. As the saying goes, “feed the soil that feeds the plants.” The main reason natural organic plant food items are better is the process by which they deliver their nutrients. They are as good as slow-release fertilizers can get, as they are digested by soil microorganisms, which then release the nutrients in a form available to plants.

This natural process not only encourages strong root growth, it also produces humus, a spongy material that enhances the structure and fertility of the soil. This natural process is a longer-lasting solution compared to the rapid response inorganic fertilizers deliver.

With natural organics, the soil is better able to hold a proper balance of water, air and nutrients until the plants need them to grow. Plants respond to this slow feeding mechanism by developing larger root systems. In turn, the top growth is more vigorous and resilient to drought, pests and diseases.

Natural Organic Plant Food Delivers Slow & Steady Feeding

With natural organics, the plant uptake of the nutrients they need is slow and steady. These essential nutrients, which release immediately in water-soluble synthetic plant food, are not in a readily available form. Plants can only use them when they are digested by beneficial soil microorganisms.

But this process requires the right conditions to take effect.

The key ingredients required for the digestion process are moisture, soil temperature and a healthy population of microbes in the soil. Moisture is necessary to sustain microbial life and keep nutrients flowing into the root zone of plants, while soil temperature is critical because as it rises, plants require nutrients more rapidly. Fortunately, microbial activity mimics these requirements and increases as soil temperature rises, so that plants can get the nutrients they need as plants require them.

Natural Organics are Safer and Eco-Friendlier

Naturally derived plant food items not only ensure the vitality of plants and facilitate organic soil processes, they also reduce rates of leaching, which is good for your garden and the environment. But more importantly, the nutrients essential for plant growth remain in the root zone until the plants need them.

On top of that, these plant food products have a significantly lower salt index compared to synthetic varieties. This means there is little to no risk of dehydrating (burning) plants when over-applying or during periods of extreme drought. Ingredients for these plant food items are byproducts from meat-processing and commercial farms, so much like composting, you’re also recycling to feed plants.

Natural Organics Have More than Primary Nutrients

By enriching your soil with natural organic fertilizers, you’re also feeding your plants organic matter from millions of beneficial microbes, such as fungi, bacteria and protozoa.

These microbes improve soil structure for better drainage, aeration, and moisture and nutrient retention. Not only that, your plants also receive secondary and trace nutrients, as well as minerals, growth hormones and vitamins that promote optimal plant growth and resistance from climate extremes, diseases and harmful insects. Organic farms swear by these products or methods of enriching the soil due to these benefits, but also because they are inexpensive and result in higher, bigger and tastier yields.

It is for these reasons that we always use natural organics as the primary source of nutrition in our Tone line of products. For years, we’ve proven that Espoma Tones are the finest, safest and most reliable plant food products available.