Maintaining proper soil pH and fertility is essential for success in gardens. Whether you’re hoping to grow beautiful flowers or tasty vegetables, plants need essential nutrients just like any other living thing. Extension typically recommends selecting a fertilizer for your garden that matches the needs of what you’re growing and your soil test report. Animal manure can be a great addition to gardens as it can provide both nutrition and organic matter to your soil, but there are a few things to keep in mind.
In this context, animal manure refers to the waste products of farm animals like poultry, cattle, horses, and small ruminants. You should never apply waste from dogs, cats, pigs or other pets in your garden, as they are more likely to have parasites and bacteria which can harm human health. One word of caution – if livestock are grazing fields treated with herbicides containing glyphosate (such as Grazon or Roundup), those herbicides will still be active in the manure of those animals. Putting herbicide-contaminated manure in your garden will hurt or completely prevent growth of your desired plants. Always double check with your source to determine whether the pastures or hay fields have been treated with herbicides before using that manure.
When we talk about manure as a soil amendment, there are two forms we can use: fresh manure and composted manure. Fresh manure usually has high amounts of ammonium and soluble nitrogen, contains lots of viable weed seeds, and can contain high levels of E.Coli bacteria. Therefore, you should never apply fresh manure to a food garden, as the risk of human illness is high, nor to one that is actively growing, since high salts and nitrogen will damage seeds and young plants. If you want to use fresh manure, it is best to apply it at least 4 months prior to planting and till it into the soil to a depth of 6-8 inches.
The better option for using manure in the garden is manure that has been composted. Composting is a specific process by which manure is maintained at the correct temperature (140 degrees F) for bacteria and weeds to be killed off and the individual components of the manure to break down into a more uniform state. Composted manure has lower nitrogen and salt content than fresh manure, which means it is less likely to harm seeds and young plants. However, this means you may need to supplement additional fertilizer to meet the nutrient needs of your plants. Furthermore, the composting process kills the majority of weed seeds and bacteria such as E. Coli that could be harmful to human health. Even with composted manure, we recommend waiting 1 month after application to plant your garden.
The nutrient content of manure is extremely variable, so it is difficult to determine exactly what affect the manure has on soil fertility unless you soil test. If you add manure in the fall, you can soil test in January or February prior to planting to determine what additional amendments you might need. As a general rule of thumb, it is recommended to apply 2-3 inches of composted manure to the garden each season. Over 1,000 square feet of garden, this would be around 150lbs of composted cattle manure, 200lbs of composted horse manure, or 50lbs of composted poultry manure.
If you have questions about gardening or soil fertility, please contact us at uge3181@uga.edu or 706-359-3233.
