Skip to main content

Using Fertilizers

Most people think that when it comes to fertilizer (“plant food”), the more the better right? Don’t you want your vegetables or flowers to grow and look the best they can? Although many people do think this way, the logic isn’t accurate. First, fertilizer is not plant food but rather a series of nutrients plants need to create their own food. There are macronutrients (Nitrogen, Phosphorous, and Potassium), and then a large list of micronutrients (Boron, Zinc, Iron, Manganese, Magnesium, etc). Both macro and micro nutrients are essential to a plant’s health. Macronutrients are merely required in a larger amount than micronutrients. Different plants require different amounts of each macro and micro nutrients.

The UF IFAS website is a great resource for learning about such requirements, and determining what specifically your plant needs. (

Fertilizer can be applied in many different ways. One can use compost, compost tea (from vermicompost), or a packaged fertilizer. When using a packaged fertilizer, test your soil to determine the pH and see what nutrients are lacking. (UF IFAS Soil Testing Lab) Many people do not know that fertilizer can be acidic or alkaline, and additionally that it can also be salty. Because fertilizer tends to be salty, if one uses too much, it can burn your plants and even kill them. To determine how much fertilizer you should use, when buying in a large commercial bag, you have to do a little bit of basic math.

When you go to buy fertilizer, there will most likely be three big numbers on the front like 15-0-15. These numbers represent the amount of Nitrogen, Phosphate, and Potassium accordingly. After you research and learn how much of each macronutrient you need, as well as what the state, county, or city allows, use this worksheet as a guide. (Click the word worksheet to open up the link.) The first page will help you to determine if the element is slow or quick release. The second page will help you to determine how many actual pounds you need per 1000 square feet. Please take note that this guide is specific to nitrogen.(Note: Usually, when you are fertilizing, Florida soil doesn’t require any intake of phosphate as it is very phosphate rich.)

Fertilizing can seem like a big confusing headache sometimes. After reading the article, and doing some research, if you still feel you don’t understand, or have a question. Feel free to contact your local UF/County Government Extension for help. Always please make sure to read the label and instructions because the label is the law!

From my garden to yours,

Eden Santiago-Gomez

One Comment on “Using Fertilizers