NUTRIENT AVAILABILITY

Nutrients in animal manure cannot be substituted for those in commercial fertilizers on a pound-for-pound basis because not all the nutrients reported on a manure analysis are readily available to a crop in the year of application.

Availability of Nitrogen

Nitrogen in the organic form must be converted (mineralized) into inorganic forms (ammonium and nitrate) before it can be absorbed by roots. In general, about 50% of the organic N may become available the year of application. Organic N released during the 2nd and 3rd cropping years after application is usually about 15% and 6% of the original N content, respectively. N availability may be higher if the manure is incorporated shortly after application. Nitrogen availability varies with the type of manure, read the following publications for different types of manure:

• F-2228 - Fertilizer Nutrients in Animal Manure
• F-2246 - Using Poultry Litter as Fertilizer 
• F-2250 - Using Stockpiled Feedlot Manure as Fertilizer 
• F-2245 - Using Lagoon Effluent as Fertilizer

Availability of Phosphorus and Potassium

Nearly all of the P and K in manure are available for plant use the year of application compared with commercial P and K fertilizers. In general, a 90% availability factor is used for K and P in the manure.

OSU Poultry Waste Management Website

Poultry Litter Marketing Program

CAFO Factsheets

OCES Water Quality Program

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