From Agronomists of the
Potash & Phosphate Institute
655 Engineering Drive, Suite 110
Norcross, Georgia 30092-2837
Phone (770) 447-0335

Winter 2002, No. 3


Milk production in the U.S. continues to migrate to the West, primarily from the Southeast and Midwest. The only Western state that did not show an increase in the past five years was Wyoming. The shift in production is mainly attributed to a shift in milk cow inventory. Where there are more cows...there is more manure.

Animal manures have been applied to soil since ancient times. Although many important chemical, physical, and biological benefits accrue from manure additions to soil, a number of factors combine to make the use of animal manures economically and environmentally inefficient.

Although their use as a nutrient source and soil amendment is well documented, there are many unresolved questions regarding their most appropriate use. The perceived value of animal manure has changed in many parts of the country from a valuable product to a waste material that requires disposal.

To assist growers in utilizing animal manure as part of a fertility program, consider three essential components:

Total manure
Manure nutrients
nutrients produced
after storage losses
manure nutrients

Returning manures to crop fields can be a valuable part of the cropping system if the nutrient content of the manure is known, an estimate of the plant availability is made, and soil testing is performed to keep nutrients in balance.

A major problem with using animal manures as a nutrient source is that the ratio of nitrogen-phosphorus-potassium is not in balance with what crops require. For example, when adequate nitrogen is added to meet crop needs, more phosphorus is added than is usually required. When sufficient phosphorus is added for the crop, there is typically a shortfall of nitrogen and potassium that must be balanced with fertilizer.

Production of high quality forages and feed are an essential component to fuel the rapidly expanding animal industry. Forages remove large amounts of nutrients from soil—nutrients that must be returned in order to achieve sustainability and high levels of productivity. Animal manures are generally more difficult to manage than traditional fertilizers, but they are an important part of every animal production system, and require careful attention. A major goal of everyone in agriculture is to produce abundant, healthy food on productive farms that make minimal environmental impacts. Proper manure management can play an important role in achieving this goal.


For more information, contact Dr. Robert L. Mikkelsen, Western Director, PPI, 617 Oeste Drive, Davis, CA 95616. Phone: (530) 758-4237. E-mail:
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