How to Understand Fertilizers


Fertility of a soil is the main factor of whether a plant will grow. For a soil to be adequately fertile, it requires nutrients to feed plants. As plants grow, nutrients are depleted from the soil. If more nutrients are depleted than what is replaced, plants will cease to grow. Applying fertilizers replaces depleted nutrients and encourages flower, vegetable and fruit production. Understanding the fertilizers available at the local garden center will prevent you from making mistakes while applying fertilizer to your garden or landscape.

Step 1

Check the numbers on the fertilizer bag to determine the nitrogen (N), phosphorous (PO) and potassium (K) content of the fertilizer. The numbers represent the amount of the nutrients by weight. 14-14-14 is 14 percent N-PO-K, in that order.

Step 2

Determine the exact weight of each nutrient by multiplying the weight of the bag by the percentage of nutrient weight. For example, a 24-pound bag of fertilizer, with 14 percent N(itrogen) by weight, will have 3.36 pounds of N in the bag (24 X .14 = 3.36).

Step 3

Inspect the bag to determine whether the fertilizer is organic or inorganic. Organic fertilizers are derived from dead plant and animal sources while inorganic are made of of synthetic, manufactured nutrients. Use organic fertilizers for an organic garden.

Step 4

Check the bag to determine whether the fertilizer is slow release or quick release. Slow-release fertilizers distribute nutrients slowly, requiring fewer applications, while quick-release fertilizers supply the nutrients all at once for quick growth or a growing burst.

Step 5

Buy a fertilizer and pesticide combination if disease in your garden or landscape is a problem.


  • University of Illinois Extension: Understanding Fertilizers
  • Clemson Cooperative Extension: Fertilizers
  • Colorado State University Extension: Understanding Fertilizers
Keywords: fertilizers, understanding fertilizers, using fertilizers

About this Author

Cleveland Van Cecil is a freelancer writer specializing in technology. He has been a freelance writer for three years and has published extensively on, writing articles on subjects as diverse as boat motors and hydroponic gardening. Van Cecil has a Bachelor of Arts in liberal arts from Baldwin-Wallace College.