The Best Liquid Fertilizer For Vegetables

Liquid fertilizer being poured from a bucket onto seedlings
(Image credit: N-sky)

Even when your soil is fertile, there may be times during the growing period when your crops need a little boost with the addition of a water soluble fertilizer for vegetables. There are many options of liquid fertilizer, even organic and DIY liquid fertilizer for vegetables.

Below we'll teach you the pros and cons of liquid vegetable fertilizer, how to tell if you need it, how you apply it, and how to make your own at home.

Pros and Cons of Liquid Fertilizer

Both liquid and granular fertilizers have similar nutrient amounts, but there are differences between the two.

Nutrient Concentration

Nutrients, especially phosphorus, are more mobile in a water solution and can get to plant roots more easily. Granular fertilizer can be too strong or “hot,” containing heavier bands of nitrogen or potassium which can damage plants.

Granular fertilizer has differing amounts of nutrients in each grain, whereas liquid fertilizer contains an identical amount in each drop. Using a liquid fertilizer ensures that each plant is getting fed the same amount of nutrients at each application.


Granular fertilizers are often less expensive when bought in bulk and easier to store than liquid. However the uniformity of application with a liquid food is a plus. Liquid fertilizers are also the recommended food for tender starter plants, again owing to their consistent even coverage.


Liquid fertilizers do not store as well as granular. They tend to settle or “salt out” in cold weather. Granular foods are also available in slow-release forms which may be more suitable for some plants.

Do I Need to Apply Liquid Fertilizer?

Whether or not to fertilize depends on a number of factors. If the plant is in an active growing or production phase, if it is naturally a heavy feeder, and if the soil is nutrient-deficient are all considerations when deciding if you should use a supplemental fertilizer. Foliage color and plant vigor are two visual cues that can help determine if your plant needs fertilizer.

A soil test can help to determine if there are elements lacking or low in your soil, and can tell you how you can amend accordingly.

There are 16 elements involved in plant growth. Air and/or water provide carbon, hydrogen and oxygen. Calcium, magnesium and sulfur are secondary macronutrients that are usually present in sufficient quantities, while the remaining 7 nutrients (micronutrients) are also usually available in soil in the nominal amounts a plant needs.

Larger quantities of nitrogen, phosphorus and potassium, however, are often needed in larger quantities that can only be provided by supplemental fertilizer.

How to Use Liquid Fertilizer for Vegetable Gardens

Feeding your vegetables is quite different than feeding your lawn. Look for a well-balanced food, 5-5-5, that contains 5% each of nitrogen, potassium and phosphorus. Do not use a high nitrogen food during mid-season at the peak of growth, as this will encourage foliage rather than veggie production.

When possible opt for an organic liquid fertilizer, such as a fish emulsion. Apply liquid fertilizer as often as once a week either at the root system or leaves. Foliar applications allow the plant to uptake the nutrients more rapidly than ground application. It is short acting, however, so it’s really best to correct mid-season deficiencies or to supplement soil applied liquid nutrients.

DIY Liquid Fertilizer

A DIY liquid fertilizer costs less and allows the maker to know exactly what is in the fertilizer. A DIY fertilizer is simple to make. The only real mistake you can make is to allow it to ferment too long, which can concentrate the salts that can damage or kill your plants. Also, be sure to only apply around the base of the plant, always taking care not to splash on the foliage.

Make a small rather than large batch of DIY fertilizer. The mix is highly biologically active and can easily tip over into overload if kept for too long. The mixture smells unpleasant, but when it has over-fermented it smells horrible. Discard any DIY fertilizer after about four days.

One way to make a quart of DIY liquid fertilizer, place 4 tablespoons (57 g) of processed poultry manure or blended dry organic fertilizer into a quart (946 ml) jar and fill with lukewarm water. Stir and cover. Allow to sit at room temp for a couple of days. Then dilute the mixture prior to use. For seedlings, use one part DIY fertilizer to four parts water.

Amy Grant

Amy Grant has been gardening for 30 years and writing for 15. A professional chef and caterer, Amy's area of expertise is culinary gardening.