Using Animal Manure as Fertilizer

The calendar may say February and the forecast is for freezing temperatures, but that does not stop me from yearning to be outdoors in the garden. While it is too cold and too wet to garden, I have been reading about the use of animal manures as fertilizer. There is a lot to learn. Allow me to summarize a few important points.

Animal manure provides the big three – Nitrogen, Phosphorus, Potassium – as well as micronutrients. It is also a good source of organic matter, which improves soil structure. Horse, cow, sheep, and chicken manures are used in farming and gardening. They have different levels of nutrients. Because fresh manure potentially carries pathogens like E. coli, it should never be used on fruits and vegetables. Composted (heated and aged) manures do not share this danger. For flower beds and lawns, fresh manure can be used but should be tilled into the top six inches of the soil within hours of application so that the nitrogen does not dissipate into the atmosphere.

Chicken manure, especially, will harm or kill plants if it is used fresh from the hen house in large quantities. It is considered a “hot” manure, containing a lot of ammonia. Horse manure is typically loaded with grass and weed seeds. Unless it is composted before use, those seeds will germinate in the garden. The downside of composting manure is that aging allows some of the valuable nitrogen to leach out into the air. Cat, dog, and pig manures are never used since they can carry pathogens that survive heat and aging. My favorite manure (is it weird that I have a favorite?) is composted rabbit manure. I am searching for a new source, since the rabbit farmer from my past has retired. Rabbits produce manure in neat little pellets that spread easily. My peonies put on an amazing performance when sprinkled with rabbit doo, that I have not been able to replicate with any other product, organic or chemical.

The contents in bags of “composted manure” that we buy at garden centers have been heated and aged so that any weed seeds are killed and there is no odor. Because the moisture is mostly gone, it is light in weight and easy to spread. Approximately 75% of phosphorus and 85% of potassium are still available in manure that has been aged for a year, but nitrogen content is much lower than fresh manure, so it is best to consider these products as a means of adding organic matter. The mild nutrient addition is just a bonus.

As always, the best way to know what your garden needs is to have a soil analysis. Don’t guess – soil test. There is still time to submit a soil sample to your Extension office and receive results before spring planting commences.

For interesting reading, follow this link to read How Animal Manure Could Help Reduce Agriculture’s Carbon Footprint by Emma Gosalvez, a 2020 article published by NC State University College of Natural Resources: https://cnr.ncsu.edu/news/2020/11/how-animal-manure-could-help-reduce-agricultures-carbon-footprint/

Do a Soil Test!

With cooler autumn temperatures comes the inevitable fall garden cleanup – raking leaves, pulling out dead annuals, removing spent flowers. Do not prune any shrubs right now that will bloom in early spring or you will be cutting off their flower buds. Instead, prune those early bloomers (azalea, for instance) immediately after they bloom. Shrubs that bloom in mid-summer or later can be pruned now, since they do not set their buds until spring time.

This is the ideal time to take a soil test. I live on an old farmstead that has been owned by my husband’s family since 1773. We live in the home built by his great-grandfather in 1885. That great-grandfather, known by everyone as “JR,” kept a daily journal of all farm events, so I know that the gardens and fields were regularly dosed with copious amounts of manure. Gardening was properly called “farming” in those days, and everything grown was “organic” of necessity.

When I started gardening here, I should have performed a soil test to determine what nutrients were needed. Instead, I threw out large amounts of 10-10-10 fertilizer, which is to say equal amounts of Nitrogen, Phosphorus and Potassium. I assumed that formula would fill any needs of hungry plants. During the early years of my marriage, my husband gave me a book, Martha Stewart’s Gardening. It was filled with wonderful photographs and stories of success, and motivated me to take my gardening more seriously. I copied Martha, distributing huge amounts of triple superphosphate.

It was not until I became a Master Gardener in 2002 that I used the testing kit provided by the local Extension office to access my soil’s needs. Imagine my shock when the results showed an almost-toxic level of phosphorus. Unlike Nitrogen, this element is slow to leach from the soil. Applications of manure and non-organic fertilizer granules had over-accumulated the phosphorus element in my soil. It was time to stop with the balanced formulations and apply only those elements needed. In my case, this meant only Nitrogen. It has taken six years, but my soil is now returning to a fertility state that makes most of my plants happy and healthy.

Please, if you only do one chore this winter, make it a soil test. The instructions for gathering your soil sample are printed right on the bag in most states. If not, your Extension office will give you an instruction sheet. The proper balance of nutrients is important. The test is inexpensive and the results are provided in terms that even neophyte gardeners can understand and follow. Just do it.