Monday, January 28, 2013

Soil 101 Pt 2- Compost & Manure as Amendments

Since posting Soil 101, we have had great questions asked and thought this would be a good addition to the topic. Most of this info was gathered from my personal notes and Soil Science textbook used in my horticulture class in college. 
Manure Composition 
When compared to commercial fertilizers, all manure is relatively low in nutrient levels. 
It releases nutrients slowly and only when the soil is warm and moist enough for microorganisms to break down the components. While each batch of manure will vary in nutrient content, horse and cow manure have more similarities than differences.

Manure isn't made up of feces and urine alone. By the time it reaches your garden, manure may include animal feed, bedding, soil, plant matter and many other materials. The amount of nutrients in the manure will be directly affected by the quality and composition of the animal's diet, as well as its size and physical condition. You would have to analyze a sample to know the exact breakdown of its nutrient content. For most home gardeners, that level of detail isn't necessary.

Cow Manure
When nitrogen, phosphorus and potassium levels are analyzed for cow manure, a distinction must be made between dairy cows and beef cattle, primarily due to their different diets. Within the dairy cow group, calves, heifers, lactating cows, dry cows and veal calves will show variations. The size of the cow also affects the nutrient levels in manure from beef cattle. For cow manure, in general, nitrogen will vary from 0.5 to 2.0, phosphorus from 0.2 to 0.9, and potassium from 0.5 to 1.5.

Horse Manure
The variation in nutrient composition between batches of horse manure depends on what the horses were fed. Manure from horses eating all forage has a slightly lower nutrient content than those fed a 50-50 mix of grain and forage. In horse manure, nitrogen tends to range from 0.5 to 2.5, phosphorus from 0.3 to 2.5, and potassium from 0.5 to 3.0. 
Fresh or Composted Manure 
Nutrient levels are highest in fresh manure, but it may contain weed seeds, salts and disease-causing bacteria and viruses such as Salmonella and E. coli. To avoid contamination of edible plants, do not apply fresh manure on crops that grow near the ground and are eaten raw. Whenever fresh manure is used, wait three to four weeks after applying before you plant seedlings. Composting manure removes the issue of weeds seeds, salts, bacteria and viruses. You can apply composted manure at planting time or use it to side-dress growing plants. 
 Because the nutrient value is relatively small for both horse and cow manure, it's best to consider them soil conditioners rather than fertilizer. As a soil conditioner, either form of manure protects against erosion, helps the soil absorb water, improves drainage, creates better soil structure and enhances microbe activity. Whichever manure is more readily available is the best one to use. If you have access to both horse and cow manure, put them both to work in your garden.

How common manures measure up
Manure Chicken Diary cow Horse Steer Rabbit Sheep
N-P-K 1.1 .80 .50 .25 .15 .25 .70 .30 .60 .70 .30 .40 2.4 1.4 .60 .70.30 .90
Sources: Rodale's All-New Encyclopedia of Organic Gardening.

Chicken manure
Poultry manure (chicken in particular) is the richest animal manure in N-P-K. Chicken manure is considered "hot" and must be composted before adding it to the garden. Otherwise, it will burn any plants it comes in contact with. Because chicken manure is higher in Nitrogen than other manures, it is best used for vegetables that their leaves are eaten. Again, I always tell gardeners to experiment and create their own personal gardening preferences and styles.

Chicken manure composting gives the manure time to break down some of its more powerful nutrients so that they are more usable by the plants.
Composting chicken manure is simple. If you have chickens, you can use the bedding from your own chickens.
Remove the chicken manure and shavings from your coop. You can put your compost pile in a compost bin, or pile on the ground (a pile about 3’ high and 5’ wide.) Mix equal parts of topsoil or dry grass clippings, dry leaves, sawdust, newspaper or hay to  manure and mix well.

Lightly wet the compost pile down and cover it to keep compost warm and improve decomposing process. We use a large dark colored tarp.

Allow the manure compost pile to decompose. If using a compost bin wait at least 60 days, (follow manufactures instructions for the type of bin being used.) For a pile on the ground, wait 6 months.  Rotating the soil or stirring it every so often and covering it again will speed up the decomposing process.

The compost is ready when it is dry and loose, it will have a slight sweet smell and be nice and dark. Till compost into your garden 1 part compost to 2 parts soil.

General Compost
Plant materials, grass clippings, kitchen vegetation scraps, dried leaves can all be composted and turned into a great soil amendment and fertilizer. It can be composted mixed into manure that you are composting or it can be composted separately. I just mix everything together and compost in two bins. When one is half full I start piling into the next one. 

Compost Accelerators 
Composting takes time, to speed up the process you can add natural accelerators that are high in protein. Protein causes the materials to break down faster and encourages beneficial micro organisms to multiply and eat up your garbage and turn it into garden gold. Some accelerators are soy bean meal, cottonseed meal, high protein chicken mash and high protein dry dog food.  
Add about 1 qt of accelerator material to pile when raw and mix in with garden fork. Turn compost as usual at designated times and add water and keep warm.


  1. Thanks for that chart. I knew my two pet rabbits earned their keep by contributing their tidy little pellets to the garden, but had no idea the nutrient values were that high. Grayson and Babbit will be delighted when I tell them.

    Over the years, I have given first dibs on the rabbit enriched compost to our pepper plants, Plant condition and yeilds were noticeably better in the seasons when we had rabbits. Think I will save a bit out for the Costata Romanesca Zucchini this summer. See if it might help the plants resist mildew .

    1. Glad to help Lillian. I have never used rabbit manure, but good to know it works well.