People like manure because it’s cheap and increases the organic matter of our sandy soils. It improves soil structure, which leads to better water storage capacity, which is again great for us. It also increases aeration, which is good because even sand can compact. This improved structure allows for better root growth, resulting in better plant growth and health. Organic matter also promotes earthworms, meaning if you add it they will come, so no need to buy earthworms to add to your soil.
Manures provide nutrients including nitrogen, phosphorus and potassium and even some trace nutrients that, while not used in large amounts by plants, are a nice benefit. The amount of nutrients in manure depends on the animal species, age of the animal, its diet, any bedding or other material that’s mixed in with the manure, the age of the manure and moisture content. Of the nutrient values of basic manures, poultry is at the top, followed by the rest. However, it’s not all good in that with most manures there isn’t an abundance of nutrients, particularly nitrogen, so you need a large volume of manure to provide the nutrients for good, positive plant growth.
It’s common to ask if manure should be applied “fresh” or composted first. The problem here is that many think composting means just putting manure in a pile and forgetting about it. But that usually only results in a mostly un-composted pile of old manure. Composting is a specific process of mixing manure and plant material and doing that in a way so the compost pile heats up significantly, meaning between 130 and 170 degrees.
The concern with fresh or uncomposted manures is the possibility they contain E. coli. As such, if you want to use fresh, raw, un-composted manure and are adding it to an area growing vegetables or fruits, it should be worked into the soil no less than 120 days prior to the harvesting of a product where the edible portion — the vegetable or fruit — might touch the ground. If the fruit or vegetable will not touch the ground then add the fresh manure at least 90 days prior to harvest. That said, most would suggest it better to either compost the manure or work it into the soil in the fall.
The reason that good quality hot composing is the best way to handle manures is that it converts the nutrients into more stable organic forms that provide a slow release of nutrients. In the raw form there is a more rapid release of those nutrients. When adding organic matter to the soil you increase the numbers of microbes, etc., which help break down those slow-release organic forms. With composted manures you get a release of about half the nutrients in the first growing season after soil incorporation, and the other half as time progresses. The downside of this is that during the plant’s main growth phases, even when applying large amounts, the nutrient availability may not keep up with plant nutrient needs. So if using manures you might need some additional fertilizer, especially nitrogen, during the main part of the growing season to reach the best productivity.
A downside to using manures is the potential for salt buildup in the soil. Salts in manures come from the various feeds and concentrates. As they accumulate in the soil the salts can inhibit plant growth and productivity. A simple fix would be to apply 6 inches or so of water over about 24 to 36 hours to flush the salts past the root zones of the plants. Also, while phosphorus and potassium levels in manures aren’t high, repeated applications over years can result in high soil levels that could leach into water systems.
So, it really is no bull that manures are beneficial — just use them wisely.
Thought for the day: “You got to have smelt a lot of mule manure before you can sing like a hillbilly.” —Hank Williams
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