Manure can be defined as the dung and urine of animals. However, the term manure is really non-specific, and can also include wastes not included with livestock excrete, such as milking center wastewater, contaminated milk, hair, feathers, or other debris. The material may also contain bedding, spilled feed, water, or soil (Rynk, 1992).

The most common domestic sources of manure are horses, cattle, goats, sheep, pigs, rabbits, and poultry. The manure of these animals differ in their nutrient contents. Chicken manure is the richest in nitrogen, phosphorus, and potassium (N-P-K). Chicken dung must be composted before it is used or it will burn the plants with which it comes in contact. Horse manure is richer in nitrogen than cow or pig manure, and also must be composted before being applied to the fields. Pig and hog manure is highly concentrated, but is less rich in nitrogen than horse manure. Cow manure is moister and less concentrated than the other manures. It has low nitrogen content and ferments relatively slow.

There are several advantages of applying manure to agricultural fields. Apart from the nutrients discussed above, manures also modify the physical conditions of the soil, by improving water-holding capacity, aeration, and drainage, and increasing aggregation. The dark color of manure also causes the soil to heat up faster. Furthermore, manure provides energy for increased microbial activity and acts as a buffer in the soil by means of its high absorption capacity. This protects the soil from excess mineral salts and toxic substances (Lampkin, 1990).

There are also disadvantages to using fresh manure. These include weed seeds and disease pathogens which may pass through the animals and onto the fields. The nitrogen in fresh manure is also very unstable, and may be lost through leaching and volatilization. Furthermore, fresh manure is quick-releasing, making 90 percent of its nitrogen available in the first year. These problems can often be solved by composting. The high temperatures generated in a compost heap are effective in the killing of weed seeds and diseases. Microorganisms in the compost pile also fix the nitrogen, reducing leaching and volatilization and resulting in slow-release of the nutrient.

Several criteria should be considered when deciding on whether to use fresh manure or compost. Compost should be used if the objective is for the long term benefits, such as soil fertility. Conversely, manure should be applied when looking to the short-term, such as an immediate boost in yield levels. Compost should be considered if there is a surplus of manure, the soil type is sandy to sandy loam, and there is a nitrogen surplus in the crop rotation. Compost is also better before crops with a long vegetation length, light nutrient requirements, and a high nitrate risk.

Fresh manures, on the other hand, are better suited when there is a shortage in the quantity of manure, the soil type is loamy to heavy soil, there is a nitrogen deficit in the crop rotation, and the succeeding crop has a short vegetation length, heavy nutrient requirements, and a low nitrate risk (Lampkin, 1990).

The amount of nitrogen available to the crop in the spring greatly varies depending on the time of application. Fresh manure may lose all of its nitrogen content if applied in the preceding autumn. Nitrogen availability increases as you get closer to the spring season (refer to Figure 3). The amount of nitrogen that is lost from the manure also increases as the time between application and incorporating it into the soil increases. Manure left unincorporated on the soil surface can lose up to 30 percent of its nitrogen after four days (Lampkin, 1990). Therefore, manure should be plowed into the soil as quickly as possible.