These substances should be monitored to avoid build up in the soil to excess or toxic levels. This information is available from a laboratory manure analysis and should be monitored by soil testing where manure has been applied. Since only inorganic forms of nitrogen and phosphorus are available to plants, only a portion of the total nutrients can be utilized in the year of application. This can be advantageous for the crop because not all of the nutients from manure are immediately available. The slow release of nutrients minimizes possible crop injury and prevents excess nutrients from being lost before plant uptake occurs.
Organic nitrogen is determined by the difference between total nitrogen and ammonia nitrogen.
Soil testing should be conducted to confirm the actual amount of available nitrogen in any specific situation. In some cases, it may be necessary to add a starter fertilizer to ensure the crop has enough nutrients available during its early growth stages. Field and laboratory methods of manure analysis are available. Field test kits allow for immediate estimation of nitrogen content and should be checked against a laboratory analysis first. Manure analysis from an operation should change very little from year to year if there are no major changes in feed ration or manure storage.