Feeding your lawn or garden is an important part of growing a vibrant yard. And a balanced 10-10-10 fertilizer seems like the best, low-hassle option. Or is it?
The specific ingredients that contribute to NPK differ from brand to brand, and can include ammonium hydroxide, urea, ammonium nitrate, phosphoric acid, and potassium hydroxide.
Many of these are actually salt, though, which can lead to salt-buildup in the soil.
- 10-10-10 fertilizer is a general purpose fertilizer that is less likely to burn plants and lawn than fertilizers with higher percentages of nitrogen. You still need to be careful how much you apply.
- Certain houseplants require regular feeding with a balanced 10-10-10 fertilizer. Since most houseplants have little microbiology to break down organic fertilizers and their runoff is less likely to end up in untreated groundwater, this synthetic fertilizer may be your best choice.
- 10-10-10 fertilizer can feed your plants too much nitrogen, phosphorus, and potassium.
Plants need different ratios of NPK based on what is already available in the soil and on their growing cycle, with more nitrogen when growing green vegetation and more phosphorus and potassium when flowering and fruiting.
Too much of one nutrient can cause nutrient deficiency, as the plant can’t absorb enough other nutrients.
- Sometimes 10-10-10 fertilizer includes iron or calcium, but mostly, it doesn’t include other micronutrients that plants need to grow and thrive.
If growing herbs and vegetables, this means that they’re less nutritious. Plants can’t contain nutrients like iron or calcium if they don’t have access to them.
- Even slow-release synthetic fertilizers quickly leach away, meaning that you have to continue to apply fertilizer more often than compost. The chemicals may then contaminate wildlife spaces and groundwater, killing fish or fouling drinking water.
- Synthetic nitrogen destroys the beneficial microbiology living in the soil. For lawns, this means thatch builds up quicker since there’s nothing to decompose it before the thatch swallows up your grass.
For gardens, plants are more likely to get infected by disease or attacked by pests, and become reliant on more fertilizers to grow as they can’t rely on nutrients from decomposing organic matter.
Without organic matter, the soil becomes prone to erosion and compaction.
- Synthetic fertilizers are made from caustic chemicals. You should wear protective clothing when handling and not allow it to touch your skin.
Never apply it when children, pregnant women, or pets are around. They can also cause a lot of different fatal illnesses, from cancer, to immune system problems, to Blue Baby syndrome.
- The ingredients commonly found in synthetic fertilizers like ammonium nitrate, calcium chloride, and potassium sulfate, are actually salts. A bit of salt is fine as rain will carry them away before they cause problems.
But when you apply fertilizer in dry weather or you apply a lot, like with 10-10-10 fertilizer, then salt levels build up in the soil, burning roots and killing plants.
Organic fertilizers have lower percentages of NPK, and if you’re using your own compost, the ratios will vary based on what goes into it.
But you don’t actually need a perfect 10-10-10 fertilizer ratio to grow crops.
Most organic fertilizers like compost will already contain enough NPK and micronutrients to grow your crops. And adding specific organic components can raise nitrogen, phosphorus, and potassium as needed.
Most organic fertilizers are better for your health and the environment than synthetic sources, although you need to wear a mask when handling any fine powders, especially blood and bone meal.
They feed the beneficial microbiology in the soil, which then feed and protect your plants. By adding organic matter to your soil, you’ll also aerate the soil and prevent erosion.
Using a soil test to determine the amount of nutrients already in your soil, you can mix and match organic sources to find the right ratios for your garden.
If the appeal of 10-10-10 fertilizer is that you can just pick it up and apply, then go for a layer of green manure compost – 1/2-inch for lawns and between 1 to 2-inches for gardens.
The Oregon State University Extension Service lists the following NPK values for organic materials, although they may vary from source to source.
1.5 – 3.5%
0.5 – 1%
1 – 2%
Ratios depend on compost batch
Vermicompost / Worm castings
0.5 – 4%
0.2% – 1.4%
0.5% – 2%
NPK differs based on source & animal. Cow and horse manure must be aged first.
Wear a mask when handling dry blood meal; use blood meal from quality sources only
A great vegetarian alternative to blood meal.
Cottonseed meal (dry)
4 – 6%
2.5 – 3%
Acidic. A great vegetarian alternative to blood meal.
Ground up; wear mask when handling.
Expensive per quantity
Fish meal (dry)
Nitrogen & Phosphorus
4 – 6%
2 – 6%
15 – 27%
Phosphorus & Nitrogen
4 – 13%
3 – 7%
Want to learn more about naturally adding nitrogen to your soil? We have a guide for that!
If you can apply organic fertilizers instead, go for it. They’ll include other micronutrients, and your garden and lawn will be happier for it in the end.
The one time I’d say that a synthetic fertilizer may be better than organic is when applying to houseplants.
Since houseplants grow in small pots without a lot of microbiology action happening, most organic fertilizer simply won’t break down. However, I’ve heard good things about using fish emulsion and liquid kelp.
According to Summer Rayne Oakes of Homestead Brooklyn, houseplants that require a 10-10-10 fertilizer include:
- Anthurium sp.
- Spathiphyllum sp.
- Zamioculcas sp.
- Pachira sp.
- Oxalis sp.
- Peperomia sp.
- Ficus sp.
- Cissus sp.
- Strelitzia sp.
If you decide to use synthetic fertilizers on your lawn or garden, here are some handy tips:
Why spend the time and money fertilizing when you don’t need to? Find out what nutrients your lawn or garden is actually missing.
You’ll avoid nitrogen burn and other problems, and you may find one of the above organic amendments will do a lot more for your garden than a general fertilizer like 10-10-10.
Measure with a tape measure how big the area you want to apply fertilizer to is, so you can figure out how much synthetic fertilizer you should actually add.
When in doubt, always use caution and apply less. It’s much easier to help a land with slight nutrient deficiencies than it is to treat nitrogen burn and dying plants.
Quick-release fertilizers are more likely to burn your plants as, like the name says, it releases its nitrates faster.
Slow-release fertilizers will keep releasing smaller amounts of fertilizer over a longer period, reducing the risk of nitrogen burn.
For cool-season grasses, that’s in the spring and fall. For warm-season grasses, that’s in the summer. Not sure which your grass is?
Cool-season grasses turn brown in the summer heat, while warm-season grasses flourish.
When you apply fertilizer to your lawn outside of its vigorous growing season, then you’ll end up killing your lawn as it struggles to deal with the stress of heat or cold along with a big dose of NPK.
It takes longer, but you’ll get a more even coverage, which means you won’t have stripes or nitrogen burn patches.
Before you use any synthetic fertilizer, get a soil test done. A soil test will tell you how many nutrients you already have in your soil.
That way, you don’t build up excessive levels of any nutrient, especially NPK. And why put your health, your family’s health, and the environment at risk when you don’t have to?
Safety tips include:
- Wear a mask, protective gloves, and a mask when handling 10-10-10 fertilizer.
- Don’t apply around kids, pregnant women, or pets.
- Don’t apply on windy days.
- Choose granules over liquid. Remember, these are caustic chemicals you’re spraying into the air and wherever the breeze takes it. Granules will remain where you apply them on the ground.
Before you apply any fertilizer at all, know why you’re doing it and what your options are. You may find the 10-10-10 to be your best option, or you may find that an organic compost or amendment will give you much better results with less hassle and less harm to your health and the environment.