Adding manure to soil improves the soil's texture and water-holding capacity while providing nutrients needed by growing plants. Unfortunately, fresh manure can also contain bacteria that can contaminate vegetables and cause human disease.
Always use composted manure
Unless you are starting a new bed that you don't plan to plant for some time, it's best to use composted manure in the garden. Fresh or raw manures are more concentrated in nutrients and will burn your plants.
To Minimize the Health Risks Associated with Using Manures in Home Gardens. Wait at least 120 days after applying raw or aged manure to harvest crops that grow in or near the soil (root crops, leafy greens, strawberries). Wait at least 90 days for other crops.
Cow manure is a great all-purpose fertilizer. It's low in nitrogen so it won't burn your tender plants, and has a good balance of nutrients. What's more, since a cow's four stomachs digest its food so thoroughly, very few weed seeds make it through, so you don't have to worry about them.
Blending manure into the top layer of topsoil will help encourage root growth and health because the manure is packed full of nutrients. The main nutrient released is nitrogen which is needed for plants and vegetables to grow in a sustainable manner.
Manure is a valuable soil amendment for home gardens. Animal manure is a valuable soil amendment for home gardens. It not only supplies primary nutrients (nitrogen, phosphorus and potassium) and micronutrients for plant growth, but also is a source of organic matter.
Horse manure can also be used in throughout the year and needs no special treatment. Just scatter it over your garden area and work it into the soil. It's as simple as that! Horse manure can be a great way to give your garden a boost.
Vegetable root crops such as beets, carrots, radishes, and potatoes are particularly sensitive to adding horse manure. Salad greens are another vegetable type that can be damaged or burned by applying horse muck to the soil.
All manures need to be well-aged before use in the garden. The longer you age them, the better, but the minimum is 3-6 months. Fresh manure collected from the side of the road or farms, such as sheep, cow, and horse, can be prone to containing weed seeds.
Cow manure compost can be used as a soil amendment and fertilizer. It can also replace soil entirely, but we recommend just mixing it. Because of its balanced pH, it can be used for just about any plant. Mix a 2-3” layer of your fertilizer into the soil until it has the desired consistency for your plants.
Manure that is piled and left alone will decompose slowly. This can take three to four months if conditions are ideal. It can take a year or more if the starting material contains a wide carbon:nitrogen ratio (as is the case when manure contains wood chips).
This is a good environment for microbes and earthworms that can start turning the material into soil. That's why you need stay on top of the watering if you plan on using fresh manure as fertilizer. Make sure to cover the manure with some type of mulch to keep the pile damp too.
Although the composting process will occur naturally over several months or years, with human help the entire process can be completed in as little as 4-6 weeks. Four essential ingredients are needed: oxygen, moisture, and a proper Carbon:Nitrogen ratio.
Don't Use Fresh Manure
If the manure is from a plant-eating animal, it is probably also full of weed seeds, which will not be inhibited from sprouting. If you still want to make use of fresh manure, don't apply it after your garden has been planted.
If you are offered fresh manure, create a separate bin to rot it down or mix it with your own homemade compost. Once rotted down, spread it across the soil in spring, about three weeks before planting. Gently rake the top layer to break down any lumps and mix it with a little topsoil.
During watering, sheep manure tea can be diluted and applied to plants. Providing phosphorous, potassium, and nitrogen, sheep manure is especially beneficial for growing tomatoes. To use fresh manure, you must till it into the soil 3-4 weeks before planting; otherwise, it can burn the vegetables.
As a rule, plan on allowing compost that contains fresh livestock manure to age and break down in the soil at least one month before planting seeds or seedlings, advises Judy Pray, author of "Garden Wisdom and Know-How" (2010).
Fresh, non-composted manure will generally have a higher nitrogen (N) content than composted manure. However, the use of composted manure will contribute more to the organic matter content of the soil. Fresh manure is high in soluble forms of N, which can lead to salt build-up and leaching losses if over applied.
Compost rich in animal manure is particularly dangerous for plants if it has not aged for sufficient time. This is because animal manure can produce ammonia as it breaks down, which can burn the plant roots or be toxic to the plants.
Ideally, the best manure for gardens is probably chicken, since it has a very high content of nitrogen, a need all plants have, but it must be composted well and aged to prevent burning plants. Chicken manure is a rich source of nutrients and is best applied in fall or spring after it has had a chance to compost.
Heavy feeders include tomatoes, cabbage, celery, eggplant, squash, pumpkins and melons. In addition to the amendments you added prior to planting, side dress these vegetables with a shovelful or two of composted manure after the plants have started blooming.
You can use manure onsite by spreading it as a fertilizer on an open area, pasture or field. You can also haul manure offsite for fertilizing or composting. Use caution when spreading manure on pastures grazed by horses. Don't spread manure on pastures if there are more than 1 horse per 2 acres.
Using horse manure in the garden is easy, and can take multiple forms. You can use it solely as a fertilizer, as a soil amendment, or even as the soil itself. It also can be an effective liquid fertilizer. Before planting, you can spread composted area over your soil and till it in.
Well-rotted farmyard or horse manure are excellent, but do make sure that it is at least three to four years old, as fresh manure can burn the roots of plants. Before applying your chosen mulch, make sure the ground is clear of diseased and old leaves and that you have fed and watered your roses.