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The Dirt on Compost
Posted on March 14, 2018 12:00 AM
By Paul Pugliese, Extension Coordinator and Agricultural & Natural Resources Agent for Bartow County Cooperative Extension
Garden soils can be improved and made more productive simply by adding compost. Readily available sources of compost from your home and yard include fruit and vegetable scraps, small twigs and shredded leaves.
Through proper composting, these materials will undergo decomposition and become usable soil amendments. You know your compost is ready when it crumbles in your hand and you no longer recognize the original materials.
Let’s talk more about the benefits of composting, what not to add to your compost pile, and how to know what’s best for your garden.
Natural Garden Helper
The benefits of adding manure and compost to a vegetable garden are more about creating a healthy root environment rather than adding nutrients. For example, soils that are highly compacted or waterlogged won’t have enough oxygen for roots to grow properly. Adding compost to heavy clay soils will improve drainage and aeration. When added to sandy soils or used as mulch, compost will increase water retention and reduce drought stress to plants.
Compost increases the soil’s ability to hold and release nutrients, which are essential for plant growth. Also, beneficial earthworms and soil microorganisms become more active when compost is applied.
Over time, yearly applications of compost will create a desirable soil structure, making the soil easier to work. To improve these soil properties, thoroughly mix one to two inches of well-decomposed compost into the top six to eight inches of garden soil.
Composting Mistakes to Avoid
You should never add meat, bones, grease, whole eggs or dairy products to your compost pile because they can attract rodents and other animals. Also, avoid adding weeds or diseased plants, which may cause garden problems in the future. Never use any animal feces in gardens or compost piles because parasites that may be present in these may survive and infect people.
Avoid adding hay, grass clippings and livestock manure to your compost, which can bring unwanted herbicides carried over from pastures, hayfields or lawns that have been sprayed for weeds. Some herbicides break down quickly and others can last as long as a full year in compost piles, causing damage to your garden plants.
Another reason not to use hay or manure is that even if they are sourced from fields not sprayed with herbicides, they are still likely to carryover unwanted weed seeds. You may end up spending more time or money on weed control if you use these sources for compost.
Getting Enough Nutrients
Compost is not exactly “free fertilizer” for your garden. Research has shown that most compost, even composted cow or horse manure, has less than 1 percent nitrogen, phosphorus and potassium. Compare this to a bag of 10-10-10 fertilizer, which has 10 percent nitrogen, phosphorus and potassium. In other words, it takes a lot more manure or compost to provide the necessary nutrients for a vegetable garden.
Recommended rates for initial applications of compost and manure are 100 to 200 pounds per 1,000 square feet of garden space. It would only take 10 to 20 pounds of 10-10-10 fertilizer to do the same job.
Nutrient release from compost is slow, and the nutrient content is too low to supply all of the nutrients necessary for a vegetable garden. It is usually recommended to supplement compost with some fertilizer, particularly nitrogen. Approximately one cup of ammonium nitrate, or three cups of blood meal, per three bushels (100 pounds of compost) is required to provide the additional nitrogen needed by most garden plants.
Have your soil tested every few years to determine whether supplemental phosphorus and potassium are required. The pH level of most composts is usually between 7.0 and 8.0. The slightly alkaline pH level of compost should not pose any problems when mixed into native soil and is actually beneficial for neutralizing acidic soils. However, because of the alkaline pH, composts are not well suited for use on acid-loving plants such as azaleas, blueberries and Irish potatoes.
For more information on maintaining compost piles, view the free University of Georgia Extension Circular 816, “Composting and Mulching,” online at extension.uga.edu/publications.html or call your local County Extension office.
Paul Pugliese is the Extension Coordinator and Agricultural & Natural Resources Agent for Bartow County Cooperative Extension. For more information and free farm, lawn or garden publications, call 1-800-ASK-UGA1 or visit ugaextension.org.
*Picture provided by University of Georgia Extension.