Selecting and Using Organic Fertilizers

Organic fertilizers are derived solely from the remains or byproducts of a once-living organism. One of the advantages of organic fertilizers is that they seldom burn plants due to their low analysis. The nutrients are released to plants relatively slowly over time, allowing for less frequent applications. As they decompose, they also improve soil structure. The disadvantages are that, as they release nutrients slowly, the nutrients may not be immediately available to plants.

Traditionally applied organic fertilizers are often bulky and may be difficult to handle. They are usually low in analysis and can vary greatly from source to source. For example, well-rotted animal manure is a common organic fertilizer. It varies widely in nutrient content depending on the species of the animal that produced it. Nutrients can also vary with the age and handling of the manure. 

Selecting Organic Fertilizers  |  Using Organic Fertilizers  |   Application Rates per 1,000 ft²  |  Application Rates per 100 ft²   | More Information

Selecting Organic Fertilizers

Use the tables below to select the appropriate fertilizers and application rates for your garden. The table lists the typical nitrogen-phosphorus-potassium (NPK) ratio, where relevant, as well as the content of other significant nutrients. It also lists the primary benefit of each fertilizer. Some supply particular nutrients, some help balance the content of soil minerals, and others are primarily useful to enrich the soil with organic matter.

Benefits and Average Analysis of Selected Organic Fertilizers

Using Organic Fertilizers

Although the above references provide gardeners with general guidelines on nutrients in common organic fertilizers, it does not represent a guaranteed analysis.  When applying organic fertilizers, the best practice is to be conservative in your application. Experiment with the amount applied and observe how the plants respond. More nutrients can be added if needed, but an overzealous application cannot be easily undone.

Once the amount of organic fertilizer needed is determined, spread it over the garden area and incorporate it into the top 6 to 8 inches of soil. This can be done with a garden fork, spade, or tiller.  Fall is a good time to add manure to garden spaces.  Other organic fertilizers can be added throughout the growing season when needed.

Average Application Rates per 1,000 ft²  |  Average Application Rates per 100 ft²  

Average Applicable Rate per 1,000 square feet

Application rates for low, medium, or adequate fertility soils are meant to be used in conjunction with an assessment of your soil by a soil testing laboratory, as well as your personal observations and the specific requirements of the crops you are growing.

Average Applicable Rate per 100 square feet

Application rates for low, medium, or adequate fertility soils are meant to be used in conjunction with an assessment of your soil by a soil testing laboratory, as well as your personal observations and the specific requirements of the crops you are growing.

More Information

• Fertilizing in the Home Garden
• Soil Testing Resources for Home Gardeners
• Using Manure in the Home Garden
• Composting FAQ
• How to Calculate Fertilizer Rates for Lawn and Garden
• Natural (Organic) Fertilization for Turf (publication)
• Managing Garden Soil

Photo credits: 1: Paul Maguire/AdobeStock  2: Maksims/AdobeStock