Selecting and Using Fertilizers

Looking at my lawn and landscape this week, the grass and most shrubs are green and healthy but, I realize that soon, warmer weather will be here bringing with it insect and disease.  Good cultural practices will help minimize damage but when our plants are struggling, often our first thought is to feed it.  It makes sense; when I am feeling ill, brownies always helps me.Turf and landscape, however, typically do not need much fertilizer in the summer.  If you look at natural areas, it is obvious that most plants do well without added fertilizer.  Nevertheless, research has shown that the addition of certain materials to the soil can sometimes cause plants to produce more fruit, grow faster, and reveal more and brighter flowers. So how do you know what your soil needs?  A soil test is the only sure way of determining the amount of nutrients to add to the soil. 

Soil test reports make recommendations for the amount and type of fertilizer to add. This will depend on the amount of organic matter present, your soils’ natural fertility and the crop you are growing. You can get a soil test box and information sheet from the Cooperative Extension Service.


– William M. Brown Jr.,

When deciding what type fertilizer to use, you basically have two choices: organic and inorganic.  Organic fertilizer is derived from living plants or animal wastes and is slow to break down and be absorbed by the plants. One potential drawback of organic fertilizers is that they may not release enough of their nutrients at the right time because they depend on soil organisms for breakdown of the nutrient source.  Soil organisms are dependent on soil moisture and temperature to be active.  However, the advantage to organic fertilizers is that they increase the soil’s organic content and improve the soil’s physical structure.  Some examples of organic fertilizers include: cottonseed meal, blood meal, compost, and fish emulsion.


Inorganic (chemical) fertilizers are manufactured and are in ready-to-use form for plants when applied. Examples include ammonium nitrate, ammonium sulfate, super phosphate and potassium chloride. So which type should you use? Simple, if you need a quick growth response, select inorganic fertilizers.  If you want to improve your garden soil and are not in a rush for nutrients, select an organic fertilizer.

In general, fertilizers for turf as well as your general landscape plants should be applied in late winter or spring.  This assures the nutrients will be available as these plants as they come out of dormancy.  Fertilizing in the summer can cause disease problems in cool season lawns.  Summer annuals and vegetables do best when fertilized after planting in April and May.

How to apply fertilizer typically depends on the formulation you purchase.  As a general rule of thumb, use granular fertilizers for established plants in late winter or early spring.  Apply this formulation to the ground and allow it to filter into the soil. Slow-release fertilizers are in a time-release form and are best for annuals, perennials and vegetables where you want to release a small amount of nutrients over a long period of time. You can use soluble fertilizers where the nutrients are dissolved in water and applied using a hose-end sprayer or watering can.  Specialize equipment is often needed to apply liquid fertilizers on home lawns to ensure a consistent application.

As you can tell, there is some thought involved in selecting the best fertility plan. Regardless of your choice, be sure to read the label. The biggest mistake most people make is to believe if a little works that a lot will work better. This type of thinking is not advised because it cost more, gives no additional benefit to plants, and can contribute to pollution of our lakes and streams.

This summer, take a look at the overall health of your lawn and landscape and identify plants that seem to be struggling more than they should.  Consider a fall feeding on your lawn and selected plants or throughout your landscape.  Your grass and landscape will thank you.  If you have questions about your lawn fertility, give your local Cooperative Extension Office a call.

Submitted by Andrew Rideout, Agent for Horticulture, Henderson Co. Cooperative Extension Service