Manures and What Determines Their Nutrient Value
by John Yazo
The term manure is commonly taken to mean a source of organic fertilizer in the form of excrement from farm animals, it is a lot more. Manure from an animal source is only one of the major methods that have been used throughout history to maintain soil fertility, provide a source of carbon, along with other constituents that affect soil humus content, biological activity and soil structure. Manures from animals also have their downside, they can also be a major pollutant if not monitored in soil.
There are three main types of manure used for agricultural soil management, animal, compost and plant. Manure is organic matter used as an organic fertilizer that contributes to the fertility of soil, and tilth.
Several factors determine the nutrient value of manure, type of animal, age of herd or flock, feed, feed supplements, bedding materials, method of collection, storage system, method of application, timing of application, soil texture, and the weather. Whenever any one of these factors changes, so will the nutrient value to also change.
Animal species is what determines the type of manure. A fresh manure from most species will contain between 10 - 20 lbs of nitrogen, 5 - 10 lbs of phosphorus, and 10 - 15 lbs of potassium per ton of manure. Poultry manures however, have nitrogen and phosphorus levels, and sheep manures have higher potassium levels.
The type of feed that an animal consumes is a big factor in the nutrient content of manure, 75 - 90 percent of the nutrients in feed is not used by animals and is excreted. Whenever you change the feed source, even seasonal changes of a pasture, the nutrient content of manure will change. feeds that are carefully balanced to provide optimal nutrient use by an animal, will greatly reduce the nutrients excreted in an animals manure.
Animal bedding materials absorb urine, and to an extent reduce nitrogen losses. Bedding materials provide a bigger benefit on changing the rate that nutrients are made available, than for changing the nutrient content of manure. the higher carbon content of a manure and bedding mix makes for less nutrients to be available the first year of application, but more the years following.
Collection and storage systems are two more factors that determine manure nutrient values. Manure when exposed to sun and wind will lose nitrogen by evaporation, and rain will leach soluble nitrogen, phosphorus, and potassium from a stockpile.
Determining the nutrient value of manure is a complex procedure. There are many factors that can alter manure content, including the weather.
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