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Past Articles Library | Best Garden Fertilizers

The Best Garden Fertilizers
Including Best Liquid Fertilizers and Low Nitrogen Fertilizers

Including plant, liquid, organic, and lawn fertilizer

One of the most confusing things about fertilizer is that there are so many formulations to choose from.

There are soluble, granular, slow release, organic, inorganic, specialty, foliar and more. And while that's all very interesting, the bottom line is this - all we really need or want to know is which fertilizer should be used for what plant and for what situation - right?

Well that's exactly what we did for you this month. We took several popular fertilizers and put them all together into an easy-to-use chart so you can, at a glance, see which fertilizer is going to be the best choice for your particular situation.

But before we begin, let's - for fun - test your current knowledge of fertilizers.

Quiz - How Well Do You Know Your Fertilizers?
Answers are at the end of this article

1. Your lawn is healthy, but looking yellow. Which formulation would be the best?

A. 28-3-4
B. 16-16-16
C. Compost

2. Your lawn is patchy and growth is spindly and weak looking. Which formulation would be the best?

A. Compost
B. 16-16-16
C. 15-30-15

3. Your tomato plants are growing well, and about to set fruit. Now they need to be side-dressed. Which formulation would be the best?

A. 5-10-10
B. 20-20-20
C. 10-60-10

4. When planting onions and potatoes give them some extra fertilizer. Which formulation would be the best?

A. 10-10-10
B. 5-5-5
C. 0-20-0

5. You're planting some new shrubs and trees and want to get them off to a good start. Which formulation would be the best?

A. Soluble
B. Slow release
C. Soluble and slow release

6. Many of your fruit trees are putting on good growth, but not setting fruit. Which formulation would be the best?

A. 5-5-5
B. 5-10-10
C. 10-60-10

7. The weather has been cold and your soil is slightly alkaline making some of your plants turn yellow. Which formulation would be the best?

A. Liquid Iron: 15-4-6
B. Fish Emulsion: 5-2-2
C. General Purpose: 20-20-20

8. The garden show you enter your flowers in every year is only six weeks away, but your prized dahlias are not flowering very well! Which formulation would be the best to get them flowering in time?

A. 10-60-10
B. 20-20-20
C. 32-2-3

9. A fertilizer that dissolves in water is called:

A. Foliar
B. Insoluble
C. Soluble

10. If you just don't know what to use - which formulation is always the best choice?

A. 10-10-10
B. 5-5-5
C. 5-10-10
D. Compost

The Best Garden Fertilizers Chart

Well, we hope you did great on our quiz and if you didn't, no matter, because this next chart is going to give you all you need to know about when and where to apply the most-used fertilizers.

Keep in mind however that the basics of N-P-K are still the three most important numbers on any fertilizer bag. Micronutrients also play a very important role, but if you choose the right fertilizer for the job, most likely they contain the proper micronutrients as well.

N = Nitrogen: Encourages plants to produce dark green leaves. This is the chief staple in the diet of most plants. Yellowing leaves means the plant isn't getting enough nitrogen from sources in the soil. But it only takes a little nitrogen to do the job, and if your goal is to set fruit or vegetables, you don't want to use excesses of nitrogen because you will only get overgrown plants and little to no fruit.

Nitrogen can leach quickly from the soil requiring frequent reapplication. Nitrogen applied in the nitrate form is usually inorganic, fast acting, but can leach quickly into surface and ground water. Nitrogen applied as ammonium is from organic sources (blood meal) and IBDU (isobutylidene diurea - a synthetic organic fertilizer) and is released more slowly and lasts longer in the soil.

P = Phosphorous: Stimulates root growth. All plants need it to get their root foundation off to a healthy and vigorous start so they can support all the growth on top, but root crops and bulbs especially need phosphorous to do well. Phosphorous and potassium don't move readily through the soil and should be applied near plant roots to do the most good.

K = Potassium: Is critical to the continuing health of all plants, especially during the second half of the life cycle in fruit and vegetables when the plants are setting flowers and bearing fruit. Potassium is often expressed as potash or water soluble potash. Potassium and phosphorous don't move readily through the soil and should be applied near plant roots to do the most good.

Don't Worry About The Form

Now with the following fertilizers, keep in mind many of them will come in many different forms. It really doesn't matter if they are slow release, foliar, soluble, or granular because that really just dictates how you will apply them.

Organic fertilizers work just as well, and many times better, than inorganic fertilizers so look for organic first when you can. Their N-P-K ratios may be lower, like a 5-5-5 instead of a 10-10-10, but they often have more micronutrients and will both fertilize and condition the soil. They also don't add as many salts and chemicals to your soil, and they won't leach into the surface and ground water as many chemical based fertilizers do.

Pay Attention To The Ratio

What matters more than anything is that the ratio of nutrients (N-P-K) is suited to the plant's needs at the time of application.

Last Thing To Keep In Mind

All nutrient ratios (N-P-K) mentioned in this article and chart are guidelines. There are so many different fertilizers with different ratios that you may find fertilizers that are close to what is mentioned here but not exact - that's OK. Don't sweat it. The nutrient numbers don't always have to exactly match what we have, just as long as they are close - that's good enough.

Type N-P-K Ratio Uses / Plants
Alfalfa Meal 2.7 - .5 - 2.8 Well balanced, rapidly available. A quick-acting source of nitrogen and some potash. Contains growth stimulants and invigorates the biological activity in the soil. Good for lawns, roses, and a general purpose organic fertilizer
Animal Manure (cow, dry) 2 - 1 - 2.4 Slow release. Best when composted. Its slow release makes it most valuable as a soil conditioner, and good for all-purpose garden uses.
Animal Manure (horse) 2 - 1 - 2.5 Slow release when dry, rapid release when fresh. Should be composted first, fresh can burn plants if applied too generously. Good for all-purpose garden uses and as a soil conditioner.
Animal Manure (poultry, dry) 4 - 3 - 1 Very rapidly available nitrogen and phosphorous. Should be composted first, fresh manure will burn plants. Good for bulbs, root crops, flowering and fruiting plants and trees.
Balanced Fertilizers Available in various proportions such as a 10-10-10, or
Well balanced fertilizer giving plants all nutrients in equal proportions. Good for all-purpose garden uses on trees, shrubs, flower beds, fruit trees, lawns, perennials, container plants, etc.
Blood Meal 13 - 2 - 1 Rapidly available nitrogen. Stimulates microbes in the soil. Blood meal is completely soluble and can be mixed with water and used as a liquid fertilizer. Also works best when scattered on top of the soil and watered in. Good for compost piles to speed decomposition, repels deer and rabbits, and used for yellowing plants in need of nitrogen.
Bone Meal 3 - 12 - 2 Rapidly available phosphorous. Mildly increases soil pH. Best for fruit trees, bulbs, and flower beds.
Compost (dry, commercial) 1 - .8 - 1 Balanced, slow release. Great to use for a lawn fertilizer (Read How To Compost Your Lawn). Good used in vegetable gardens as long as at least several large handfuls are used per plant and worked into the soil to make sure enough nutrients get to the plant. Good choice for the busy gardener.
Compost (homemade) 1 -.5 - 1
up to
2 - 1 - 2
Balanced, slow release. Great to use for a lawn fertilizer (Read How To Compost Your Lawn). Good used in vegetable gardens as long as at least several large handfuls are used per plant and worked into the soil to make sure enough nutrients get to the plant. Good choice for the busy gardener.
Cottonseed Meal 6 - 2 - 2 Rapidly available nitrogen that is broken down slowly and is available to the plant over a period of time. Will acidify the soil so best used for crops that prefer low pH such as azaleas, blueberries, citrus, dogwoods, hollies, and strawberries. May contain pesticide residues.
Fish Emulsion 4 - 4 - 1 Rapidly available nitrogen. Apply as a foliar spray in early morning. When used as a liquid drench, results are quicker than with other organics. It is a low-nitrogen concentrated liquid food containing a wide range of trace elements that will green foliage, grow vigorous roots and big flowers while also enriching the soil. Good all purpose fertilizer. Fish emulsion however is heat processed meaning that a lot of the nutrients and amino acids are totally destroyed during processing. The odor dissipates rapidly after application. If there is a choice, use hydrolized fish fertilizer instead of emulsified.
Fish - Hydrolized 2 - 4 - 2 Much better than fish emulsion because it is cold processed instead of heat processed and has no odor. Hyrdrolized, or cold processed fish, keeps all of its nutrients and proteins and allows them to be readily available to the plant. It also makes those nutrients water soluble, so you can use them for foliar spraying or drip irrigation, with no worries of clogging the drip line. Good all purpose fertilizer especially good for flowers, vegetables, and herbs. (Read Hydrolized Fish Fertilizer).
Fish - Meal 10 - 4 - 4 Rapidly available nitrogen. Good to be used in early spring at transplanting and any time plants need a boost. Don't scatter fish meal, because of its strong odor; plant it in a series of holes about ten inches (25 cm) deep that can then be covered with about four inches (10 cm) of soil. Good for yellowing, nitrogen deficient plants that need a quick boost.
Greensand 0 - 0 - 7 Very slowly available potassium. Can last up to 10 years. Loosens clay soils. Apply in the fall for benefits next season. Mostly used as a soil conditioner when amending.
Liquid Seaweed 4 - 2 - 3 Slow release of potassium and good source of micronutrients. Contains plant growth hormones that stimulate plant and root growth. Gives a quick boost for greening foliage, and when mixed with fish emulsion or hydrolized fish, it can't be beat because the two benefit one another in so many ways. Its growth promoting substances enhance plant development, color and vigor. Seaweed has also been found to increase plant hardiness and resistance to adverse environmental conditions, such as early frost, extreme heat. and lack of moisture. (Read Kelp Can Save Your Fruit). Used as a seed inoculant, seaweed fertilizer increases and accelerates germination, and enhances the rapid development of a healthy root system. Good for all plants as a general energizer.
Wood Ash 0 - 1 - 7 This is not a recommended fertilizer to use. It was only included here since many have questions about it. Nutrient amounts are highly variable. Good source of potassium and calcium, however it will rapidly increase soil pH. Can injure soil microorganisms. Never use without doing a soil test first to check your soil pH. Use sparingly in the spring and dig under. Don't use near young stems or roots. (Read Wood Ash As A Fertilizer).
Worm Castings .5 - .5 - .3 Well balanced fertilizer used mostly to improve soil structure. The castings slowly release nutrients needed for healthy plant growth and increased production rates for fruits and vegetables. Good for herbs, fruits, or vegetables.

Acidifying Soluble 30 - 10 - 10 Good source of nitrogen for plants that prefer acid soil conditions such as azaleas, blueberries, camellia, citrus, crape myrtle, ferns, holly, magnolia, rhododendrons.
Ammonium Nitrate 35 - 0 - 0
28 - 3 - 4
Rapidly available nitrogen. Used most often on lawns for fast greening and rapid growth. Good for yellowing, nitrogen deficient plants that need a quick boost. Leaches quickly from the soil.
Balanced Fertilizers Available in various proportions such as a 10-10-10, or
Well balanced fertilizer giving plants all nutrients in equal proportions. Good for all-purpose garden uses on trees, shrubs, flower beds, fruit trees, lawns, perennials, container plants, etc.
Liquid or Chelated Iron 15 - 4 - 6 Good for plants that are yellowing and iron deficient due to compacted or poorly drained soil. Cold weather, and alkaline soil also can make iron less soluble. Good for gardenias, boxwood, camellias, pin oak.
Superphosphate 0 - 20 - 0
10 - 50 - 10
Rapidly available phosphorous. Used to promote flowering and fruiting. Good for container grown plants, flowers, perennials, and root and bulb crops such as onions, tulips, and potatoes.


Ok, now you really have all you will ever need to know about fertilizers and when and where they are best used.

But don't forget what we learned from the quiz, the four best formulations for all around good use will always be a 10-10-10,  5-5-5,  5-10-10, or good compost.

And from the chart above, one the best organic combinations you can ever use is hydrolized fish mixed with liquid seaweed. Plants just thrive when using these two fertilizers together.

All the fertilizers talked about above are widely available in several different forms from organic, inorganic, soluble, foliar, slow-release, and granular.

Organic fertilizers are always your best first choice because of their micronutrient content and their ability to be both fertilizer and soil conditioner.

It doesn't always matter how you apply fertilizer as long as you do apply it in the correct nutrient ratio (N-P-K) for the plant's needs.

Now go feed your plants - they're probably hungry!

Fertilizer Quiz Answers

1. A. 28-3-4 and C. Compost - Either one would do a good job. A lawn that is overall very healthy, but yellowing just needs a boost of nitrogen. 28-3-4 is almost all nitrogen and compost, while maybe taking a week or two to start to work, gives good balanced nutrition with several micronutrients. (Read How To Compost Your Lawn)

2. A. Compost and B. 16-16-16 - Either one would do a good job. A lawn that is doing poorly overall needs to be given a balanced and complete food to help the entire plant system, both of these materials do that. (Read How To Compost Your Lawn)

3. A. 5-10-10 - When side-dressing you don't want to supply too much nitrogen because you will get all foliage and no fruit. Use a food that is higher in phosphorous and potassium and lower in nitrogen.

4. C. 0-20-0 - All root crops need a high phosphate or superphosphate fertilizer to help with good root production.

5. C. Soluble and slow release - Because the soluble will give the trees and shrubs an instant boost and when that starts to wear off, the slow release will be kicking in with a continual food supply for the next several months.

6 B. 5-10-10 - Whenever your goal is more fruit, a fertilizer higher in phosphorous and potassium is always the best choice.

7. A. Liquid Iron: 15-4-6 - Cold weather and alkaline soils can tie up iron, which is needed to make chlorophyll. Liquid iron can give you a quick fix until you can either adjust your soil or until the weather warms up.

8. A. 10-60-10 - Superphosphate helps with fruit and flower production.

9. A. Foliar and C. Soluble - Both terms are used interchangeably for a fertilizer that can be dissolved in water.

10. A.10-10-10, B. 5-5-5, C. 5-10-10, D. Compost - All are good choices. They are stable, well-balanced fertilizers and will give your plants most of what they need.

The writer is a member of the National Garden Writers Association, a nationally published writer, and a certified organic grower. She regularly speaks and writes about all gardening related topics, with an emphasis on making gardening a successful and enjoyable process for anyone who wants to learn. Weekend Gardener Monthly Web Magazine concentrates of giving detailed gardening tips and gardening advice to all levels of gardeners.

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