A light rain is good and helps incorporate surface applied manure. A big fast rain may not be good, increasing the risk of runoff.
Expect manure to be applied before the first cut (harvest) and after subsequent cuts (Fig. 1), because these are the times the grass crop needs the nutrients.
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).
If you have a tractor, load the bucket with compost and head to the field. Then gently nudge the bucket control arm to “sprinkle” manure over the field. You might need to follow up with a harrow to spread any unevenness. A key tip is to not drive the same path each time to avoid compaction in the tractor tracks.
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).
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.
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.
Manure may be an effective fertilizer that enriches the soil's fertility, but its use may result in some disadvantages. Manure has some potential disadvantages when used as fertilizer. It can contain weed and pest seeds, rodents and other pests, and pathogens such as E. coli.
You can spread ¼ to ½ inch of fresh or composted manure on pastures during dry weather when plants are actively growing. Test your soil to determine your plant nutrient needs; retest every few years. If you apply the manure too thickly, nutrients can contaminate water.
Adding manure to the home vegetable garden can increase soil organic matter and may alter soil structure. Adding manure to soil will not change soil texture. Fall is the most common time of year for adding manure to a vegetable garden. The manure may be spread atop the soil or incorporated into the garden soil.
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.
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.
Shred everything
Smaller materials break down faster than larger ones, and making sure everything is shredded is also a great way to create pockets of air within the pile to help aerate and speed up the composting process.
Covering your manure pile will help it decompose faster, keep it drier in the winter, and reduce mud. It also is a crucial step for protecting water quality in our local streams and rivers. Bacteria and nutrients from manure piles can move off your property in rain water and make their way into a stream or river.
Cover your manure pile with a heavy tarp and good weights to hold it down against strong wind. You will keep the beneficial nutrients and you will not be polluting streams or groundwater.
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 90–120-Day Rule
You may not apply raw, uncomposted livestock manure to food crops unless it is: Incorporated into the soil a minimum of 120 days prior to harvest when the edible portion of the crop has soil contact; OR. Incorporated into the soil a minimum of 90 days prior to harvest of all other food crops.
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.
Not all manure provides nutrients to plants. As it breaks down, manure containing lots of bedding takes nitrogen from the soil. This reduces the amount of nitrogen available to plants.
Adding lots of organic matter such as compost, farm manure, or shredded leaves to clayey soil will allow it to drain more easily and hold the right amounts of water and air for better plant growth and increased biological activity.
It should take around three months, perhaps longer in the winter when microbial activity slows. You will know your compost is ready when the material looks evenly textured, crumbly, dark-colored like dirt, and is earthy-smelling. Its temperature should be 90° F or less.
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.