Adding too much manure can lead to nitrate leaching, nutrient runoff, excessive vegetative growth and, for some manures, salt damage. And using fresh manure where food crops are grown poses risks for contamination with disease-causing pathogens.
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.
How Often Should Manure Be Applied to The Garden? At the very minimum, a garden should be fed with fertiliser twice a year: Once at the start of spring (September in the southern hemisphere, March in the northern hemisphere) for the warm season crops.
The manure may be spread atop the soil or incorporated into the garden soil. Pig, dog, cat, and human waste should never be used in a vegetable garden. Cow, horse, chicken/poultry, sheep, goat, and llama manure are acceptable types of manure appropriate for use in vegetable gardens.
Specialists at the University of Georgia recommend a rate of 150 pounds of cattle manure or up to 200 pounds of horse manure or 50 pounds of poultry manure per 1000 square feet of garden soil.
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.
Avoid applying manure on areas next to streams or riverbanks. It is important to keep the nutrients and pathogens in the manure away from surface waters. To protect yourself, raw manure should never be used in the vegetable garden and you should always wash your hands thoroughly after working with manure.
Dehydrated Cow Manure Uses:
Mix 1 part dehydrated cow manure with 3 parts of top soil. With poor quality top soil, use a 50/50 ratio.
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.
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.
Spread composted manure in your garden in small amounts, about one-fourth to one-half inches deep. Thicker applications up to 1 inch deep might be justified in poor soil with low organic matter. To prevent pollution, store compost away from water sources and cover the pile with plastic when you expect heavy rain.
Apply nutrients in the spring just before growth starts. Avoid using manures and fertilisers in late summer or autumn where they may be lost over winter and pollute water bodies.
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).
Simply ageing a manure pile for three months can kill about 60% of the weed seeds present, and bacterial counts start to drop within days after the manure leaves the animal. Then, when the aged manure is mixed into the soil, soil microorganisms clear out residual bacteria in about a month.
Applying too much manure, at the wrong time, or improperly handling it in other ways releases nutrients into the air or into ground or surface waters. Thus, instead of nourishing crops, nutrients become pollutants. Excess nitrogen can leach through soil into groundwater.
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.
On other edible crops, fresh manure applications should be made at least three months prior to harvest. With just a four month or so growing season, this means you should only apply fresh manure in the fall; not in the spring or during the growing season to any area that is or will be planted with food crops.
Cow manure adds to the balanced nutrient content of the already rich soil. It is an also an excellent potting medium for regular houseplants.
Because the manure will rot down and the soil level will sink a bit. You can just put the manure on the top of the soil and leave it, which will work. I prefer to dig it in to the soil because I find it breaks down quicker and the benefit of the manure is spread throughout the soil. It also stops lumps forming.
If, for example, your main goal is to increase your soil's organic matter, compost is likely the right pick, whereas if you're looking to boost your soil's nutrient content, manure is your better bet.