Fertilize Your Organic Vegetable Garden

Old fashioned crop duster.
Old fashioned crop duster.

The mantra of the organic gardener is "feed the soil, not the plant". If you ensure a nutrient-rich growing medium, teeming with microbiotic life, then your plants will generally feed themselves. Feeding the soil is far more practical then trying to cater to the food preferences of a dozen or more fussy crop varieties, and really saves a lot of time. This is, however, not always practical and sometimes it is appropriate, and necessary, to feed your plants by adding fertilizers.

Fertilizers are not the same as soil amendments, which add organic matter to the soil. Fertilizers may add some organic matter, but their primary purpose is to provide nutrients. And unlike compost and organic matter which "feed the soil" by feeding the micro-organisms, the nutrients from fertilizers typically go direct to the plant. So before you fertilize first determine why you need to and then decide what type of fertilizer is required and how you will apply it.

These are six common reasons gardeners fertilize:

This soil can use some improvement.
This soil can use some improvement.

You Soil Isn't Very Fertile Yet

While you are still “growing” your soil in a new garden you will need to rely on fertilizer to ensure crops have all the nutrients they need. These types of fertilizers intended to act slowly over an extended period of time and are incorporated into the soil. You’ll want to plan a 2 to 5-year soil improvement program incorporating nitrogen, phosphorus, and potassium sources, plus important trace elements such as calcium, molybdenum, and iron. Once you develop a reliable and varied source of compost you should be able to reduce the amount of fertilizer amendments and use mainly compost to feed your garden. Check out the soil improvement plan in the link to the right.

Baby lettuce tastes best when grown fast!
Baby lettuce tastes best when grown fast!

Fast Growing Crops Benefit

Fast growing crops, like lettuce and spinach, taste best when they reach maturity quickly without interruptions in the growth cycle. These speed burners of the garden need a good dose of nutrients to get them off to a healthy start. Since they are in the garden for a short period, you don’t have time to correct nutrition problems, so make sure they get what they need up front. The necessary nutrients can be added to the soil, but an additional foliar feed for the plant will ensure success.

If you live in colder climes and have a short growing window, you may also want to fertilize to ensure crops reach maturity before the first frosts of Autumn.

The first crops of Spring.
The first crops of Spring.

Help Over-wintered Crops off to a Fast Start

Many organic gardeners will plant hardy, slow-growing crops in late fall and have them over-winter under insulating layers of mulch or in cold frames. When the first warm, sunny days of early spring approach they are rewarded with an early crop that is already sprouted and ready to grow! Unfortunately, the lower soil temperatures of spring affect nutrient availability because the soil micro organisms are not very active when the ground is cool. Consequently, they are not doing their job of breaking down organic matter and making it available to plants. Feeding the plants directly will get them started; once the soil warms the microherd will get busy and start feeding them for you.

This snail-chewed pepper plant can use a fertilizer lift!
This snail-chewed pepper plant can use a fertilizer lift!

Boost Stressed Plants

Yes, even plants feel stressed sometimes. Transplanting, inclement weather, too much or too little water, and insect pests can all stress crops to the point that their immunity and resilience are weakened. If this occurs the plants are far more susceptible to disease, poor growth, and low yields. Weakened plants, like lame caribou, become favored targets for predators, which only adds to their woes. Happily, fertilizers can give stressed plants a life saving "pick me up". I always recommend gardeners give crops a half-strength dose of liquid fish emulsion or similar nutrient feed immediately after transplanting and then a full-strength dose every few weeks if less than favorable growing conditions are present or anticipated. This frequently gives the crops the extra lift they need to beat back their troubles and reward you with a bountiful harvest.

Happy heads of cabbage.
Happy heads of cabbage.

Help Maximize Yields

Okay, so organically grown crops will rarely match the size and beauty of commercially grown and fertilized veggies. That doesn't mean you have to accept scrawny plants and measly yields. A few well-timed doses of a nutritionally balanced organic fertilizer will do wonders for your garden's output. It's not cheating if the fertilizer is certified organic! Your mature crops need their biggest boost of nutrients at flowering and fruiting. A good foliar feed at these crucial times will ensure they develop their best potential harvests.

Production like this requires nutrient support.
Production like this requires nutrient support.

Feed Long Season Crops

Long season crops like tomatoes, eggplants, peppers, and squash will produce beautiful veggies for you all season until felled by frost. Such heavy duty production, however, comes at a cost because long season crops are also your garden chow hounds. They will use up soil nutrients and go begging long before they season is over, and their yields will suffer if their food source is not replenished. Consequently, these crops need a mid-season boost to get them through to summer’s end. This can be a foliar feed or soil “side dressing”, but plan on a scheduled fertilizer regime that feeds them every 7 to 10 days depending on the crop, your soil's fertility, and the growing conditions.

Reading Fertilizer Labels

Even though you are doing a beautiful job supplying your garden beds with plenty of nutritious compost, if you are still building up the soil of a newly dug bed or planting heavy feeding veggies like tomatoes and squash you will need to supplement the soil with fertilizer. The following information will help you analyze a fertilizer label and decide what is best for your garden’s needs.

Is it organic? Some fertilizer labels may say the product is “organic” even though it contains synthetic compounds. One way to ensure you are getting an all-organic fertilizer is to look for the three-leaf logo of the National Organic Program (NOP), which is overseen by the U.S. Department of Agriculture. Manufacturer’s that include the logo on their labels must conform to USDA standards that prohibit use of synthetic substances.

Another logo to look for is OMRI™ Listed. OMRI is an acronym for Organic Materials Review Institute, which reviews products to determine whether they meet the NOP standards. If you don’t see one of these logos, read the ingredient list and don’t purchase the product if you see substances like ammonium, nitrate, urea, or superphosphate.

Read the Box!

This is a compound fertilizer with a 5-10-10 NPK ratio.  It says "with natural ingredients", but that does not mean it is certified organic.
This is a compound fertilizer with a 5-10-10 NPK ratio. It says "with natural ingredients", but that does not mean it is certified organic.

Straight or compound. Some products contain a single plant nutrient. These are call “straight” fertilizers. Examples are ammonium sulfate (a synthetic product commonly used on lawns) and feather meal (an organic product). Products that contain more than one nutrient are called compound fertilizers. Typically they contain nitrogen, phosphorus, and potassium and other trace elements such as boron, calcium, molybdenum, and magnesium. Be careful when selecting a straight fertilizer because they tend to be “hotter” than compound fertilizers and may burn plants.

NPK ratio. This will say something like 10-10-10, 1-1-20, 0-6-0 or numerous other combinations. The first number measures the proportion of nitrogen in the product; the second number measures phosphorus; and the third number measures potassium. These are the three major nutrients required by plants. So a NPK ratio of 10-5-2 indicates the fertilizer has a greater proportion of nitrogen then phosphorus or potassium. A product where all three numbers are the same or close, such as 5-5-5, is called a “balanced” fertilizer. In other words, if you use this product your plants will receive an equal amount of nitrogen, phosphorus, and potassium. Knowing the NPK ratio is important if you are using fertilizers to treat a nutrient deficiency in a certain crop. (Follow the link to " Vegetable Plant Nutrient Deficiencies" for more on this). For example, if your tomatoes need a fast nitrogen boost, you may want to select bloodmeal with an NPK ratio of 11-1-0. If your green beans need more potassium, you might select greensand with an NPK ratio of 0-0-7.

Foliar feeding: like an IV for your plants!
Foliar feeding: like an IV for your plants!
Sweet peas in spring.
Sweet peas in spring.

Liquid or Solid Fertilizer?

Liquid and solid fertilizers serve different purposes so know what you want to achieve before your select your fertilizer.

The purpose of LIQUID FERTILIZERS is to provide direct nourishment for your plants, not the soil micro organisms. Types of potent liquid fertilizers include fish, kelp, or seaweed emulsion; compost or manure “tea”; or the commercial brands such as Miracle Grow (although as an organic gardener I don’t use synthetic fertilizers.) Liquid fertilizers provide a quick nutrient boost and stimulate fast plant growth, but they are a temporary measure. Do not use liquid fertilizers as a replacement for a good soil amendment program.

You can apply liquid fertilizers as a foliar feed or as a soil drench. Foliar feeds are sprayed over the plant’s leaves; soil drenches are poured over the soil around the plant to be absorbed by its roots.

Think of a foliar feed as an IV for plants. Since plants can absorb nutrients through their leaves 8 times as effectively as through their roots, foliar feeding is the quickest way to get fertilizer into their systems. They are quite useful for seedlings (which need a good deal of nutrients to grow properly), new transplants (to help them overcome transplant shock), and stressed plants (to make them strong). It is also good for leaf crops because extra nitrogen encourages leaf growth over fruit growth.

A soil drench takes nutrients to the plant’s roots, so it take longer to have the desired effect but provides more lasting help.

Tips for Use:

  • Liquid fertilizers are best applied at plant flowering, fruit set, and fruit ripening time when the plants need an extra power boost. If you are applying liquid feeds because you have noticed signs of nutrient deficiency in your plants, then use every ten days until the symptoms start to disappear.
  • Always mix foliar feeds according to directions and use them at half strength on seedlings and transplants.
  • Apply with a spray mister or fine nozzle on your hose and spray until the moisture runs off the leaves.
  • The best time to foliar feed is early evening when your plant’s stomata are open and better able to absorb the nutrients. Otherwise feed on an overcast day or in early morning so the liquid dries before the sun can damage the wet leaves. Don't foliar feed on hot days when plants close their stomata to conserve moisture.
  • Plants with waxy leaves, like cabbage, don’t respond as well to foliar feeds!

Tomatoes are heavy feeders and require a "side dressing" feed of fertilizer to produce well.
Tomatoes are heavy feeders and require a "side dressing" feed of fertilizer to produce well.
Squash and beans make good companions.
Squash and beans make good companions.

The purpose of SOLID FERTILIZERS is to provide nourishment for the microherd, the soil organisms that drive your soil’s life processes, not the plants. Consequently, solid organic fertilizers are called “slow release” because it is the action of the microherd that breaks them down and releases the nutrients in a form the plants can use. Solid fertilizers provide slow, steady growth; which is the best kind for sturdy, healthy plants.

Generally, if your soil is in decent shape you only need to add solid fertilizers once in mid-season. If you are still building your soil, fall and spring applications will be beneficial. Applications times vary with the amount of time it takes the fertilizer to break down. Phosphates are notoriously slow to break down, so don’t do much good until 3 to 6 months after you have applied them. Plan ahead for spring and add phosphates to your garden in the fall. It’s also smart to add it to your compost pile; it will be ready when the compost is and will make those compost worms very happy!

Manures, which are rich in nitrogen, are best applied in the spring because winter rains will quickly leach the nitrogen out of it. Same with the other nitrogen-rich fertilizers such as alfalfa meal or cotton-seed meal.

Tips for Use:

  • Solid fertilizers applied as general amendments in the fall to prepare for spring can be evenly sprinkled over the bed and left. The earthworms and microherd will incorporate it into the soil for you. In the spring it should be forked into the top few inches of soil.
  • Solid fertilizers applied for specific purposes, such as a boost to long season crops, should either be added to the planting hole or as a “side “dressing”. To side dress you simply sprinkle the fertilizer on the soil surface just outside the plants root line and gently work it into the top two inches or cover with mulch. Don’t allow solid fertilizers to touch plant stems as it can burn!
  • Apply solid fertilizers to moist soil. This is when microherd activity is highest and gets them to work faster!

Don't be afraid to use fertilizers in your garden. Just make sure they are organic and selected to achieve the desired effect. Then spread it around!

See you in the garden!

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Comments 4 comments

Kay Creates profile image

Kay Creates 6 years ago from Ohio

Very informative.

Teddletonmr profile image

Teddletonmr 5 years ago from Midwest USA

Fertilize Your Organic Vegetable Garden is full of useful information on organic fertilizer, vote up and useful.

Thanks Mike

ShootersCenter profile image

ShootersCenter 4 years ago from Florida

Very good article, well thought out and full of useful info.

Melis Ann profile image

Melis Ann 4 years ago from Mom On A Health Hunt

This is a very well written summary of organic fertilizer options for the garden. I'm glad to see you point out warnings and watch-outs for determining if the fertilizer is actually organic. SHARED.

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