Most fertilizer packages have instructions that give the amount and frequency of application. You can either follow those directions or feed half as much as directed but twice as often.
Dry chemical fertilizers are usually the most economical buy. Slow-release forms save the most time. Foliar feeding gives the quickest response and ensures that all the nutrients are absorbed. Liquids or soluble powders can be added to the irrigation water. Organic fertilizers add organic matter as well as nutrients. After adding any fertilizer to the soil, be sure to water thoroughly to dissolve and dilute it to keep salts in the fertilizer from harming your plants.
There are several effective ways to apply fertilizers.
This method is best for spreading large amounts of fertilizer over a large area. Lawns, trees, vegetable gardens, and flower beds can be fertilized this way. Both granular fertilizers and bulk organic materials can be spread by hand or with a spreader device, such as a lawn spreader or crank-type hand-held spreader.
To see some fertililizers suitable for broadcasting, go to Lawn Fertilizers.
Banding is often used for rows of vegetables or flowers, especially to get plants started. Place the fertilizer in a furrow 2 inches to the side of, and 2 inches deeper than, the seed furrow. Placement of the band of fertilizer must be coordinated with the watering plan. For furrow irrigation, place the band in a furrow between the seed furrow and the irrigation furrow. With overhead sprinkling, place bands on both sides of the seed furrow. With drip systems, place the fertilizer under the emitter.
Side dressing is the placement of fertilizer alongside a plant or row of plants, usually midway through the growing period. It is often used to supplement the fertilizer applied at the time of planting.
To see some fertilizers suitable for banding or side dressing, go to Plant Foods.
Watering with Fertilizer Solution
Some fertilizers, clearly marked on the package as completely water soluble, are ideal for applying as part of the watering process. You can use this method with drip irrigation and sprinkler systems and for houseplant watering.
Dissolve a small sample of the fertilizer to see if it leaves any residue that could plug up your system. If it does, you will have to strain the liquid or pour the dissolved portion into another container, leaving the residue behind.
For liquid fertilizers that do not dissolve cleanly, such as fish emulsion, apply the fertilizer with a watering can or injection device in a hose to avoid plugging up filtered systems.
Soil injection is a specialized method of applying fertilizer solution that is sometimes used with trees. A root irrigator is inserted into the root ball, and water pressure forces the fertilizer into the root area.
Spraying plants with water containing fertilizer is known as foliar feeding. Fertilizer applied in this way is readily absorbed by the leaves and can cause a rapid change in the plant’s condition. This method is often used to overcome deficiencies of micronutrients or to provide nutrients that would be unavailable to the plant through the soil, such as iron and zinc.
Using slow-release fertilizers
Slow-release fertilizers last for several months to a couple of years in the soil. They are more expensive than soluble types but are valuable where low maintenance is a goal. Select one that matches the crop you are growing. For example, select a pelleted type that lasts for 4 months to mix into an annual flower bed when you’re planting. All slow-release fertilizers depend on dampness to release their nutrients; bury them in the soil or dig them into the surface. Don’t leave them laying on the surface, or they will be less effective. When used with drip irrigation, place the fertilizer within the “onion” of damp soil.