Adding manure to soil can lessen wind and water erosion, improve soil aeration and tilth, increase soil organic matter, and promote the growth of microorganisms that are beneficial to crops. On the other hand, excess applications of manure can be harmful to crops, soil, surface and ground water quality. Heavy applications of manure also can cause excess accumulation of soluble salts in the soil, especially in some of eastern Oregon's arid regions, where little or no leaching occurs. High salt content in soil can decrease water availability, which inhibits plant growth. In addition, a large volume of manure in one application can cause temporary soil sealing, particularly in low spots.
Soil sealing increases the potential hazard of manure runoff with any subsequent rainfall.
You can then calculate the economic value of the manure according to its plant nutrient content. Although other nutrients and trace elements in the manure are beneficial to crops, it's difficult to determine the value of that benefit. Sample the manure to determine the concentration of nutrients in storage. In liquid tanks, mix thoroughly before sampling or sample at different places in the storage unit to get a representative value. Mix these together and put a sample in a plastic jug or jar with a screw lid.