By Rick Koelsch
Manure has value. That value may result from improvements in soil quality, increases in yield and replacement of commercial nutrient required for crop production. But what are the economic benefits of beef manure?
N and P value
Manure is a supplemental source of phosphorus, organic nitrogen, ammonium-N and micronutrients commonly required by many fields. Cropland receiving surface-applied manure (not incorporated) benefits from both organic N and P. The value of the nutrients in beef manure (open lot) is heavily influenced by the value of the P and to a lesser extent the organic-N (Figure 1).
Because feedlot manures and many solid manures contains little ammonium-N, incorporation to conserve N would produce little additional value.
For slurry manures, such as captured by a beef barn with a pit below a slatted floor, immediate incorporation of manure is important for gaining value from the important ammonium-N content. Slurry manures generally conserve the ammonium-N fraction commonly lost from open lots.
Figure 2 illustrates the value of incorporating beef manure with a below barn pit. About 40% of its value results from the ammonium-N conserved by direct injection.
Note the importance of P to achieving value from both of these manures. Almost half or more of each manure's value will only be realized by applying manure to fields requiring P supplementation (typically, fields with Bray soil P levels below 30 parts per million). So, farmers wanting to gain the greatest value from manure should target those fields with low soil P levels. A 25-ton load of open-lot beef manure has a fertility value of $350. However, two-thirds of this value will not be realized if applied to a field with high soil P levels.
To further enhance the value of manure, targeting those fields that have a potassium requirement offers additional value. Soil tests for highly productive fields are increasingly identifying a need for K supplementation. Manures are an excellent source of K. For the beef feedlot manure example shared in Figure 1, the manure's value has almost doubled by applying it to a field with a K requirement (Figure 3).
Economic value can also be gained from a yield response to manure. Such yield responses can be a result of improved soil structure and greater drought tolerance of the soils receiving manure or from the increased biological activity in the soil producing a number of benefits such as greater nutrient availability to the plant.
A recent worldwide literature review of 159 research comparisons of the nutrient replacement value of manure observed an average yield increase of 4.4%. Adding a 5% yield increase to a 200-bushel-per-acre corn crop will produce some additional value. However, note that this yield boost does not compare with the value of the P and K in manure, assuming a 5% yield increase is achieved.
Similar benefits are observed for manures produced in other beef systems in open lots, bedded back barns and barns with a deep pit.
Keys to manure value
Key to gaining the economic value from manure nutrients is the rate at which manure is applied. To receive the returns shown in the figures, the following practices must be followed:
• Manure should be applied at a rate that does not exceed the crop N requirements for a single year. Excess manure N application is likely to be leach beyond the root zone and be lost.
• Manure applied at rates near the crops N requirement typically overapply P and K. However, these nutrients will continue to be available to crops in future years. To gain the manure's P and K value, target those fields requiring supplemental P and K or your state specific recommendations. In addition, avoid re-applying manure to the same field until soil testing suggests need for supplemental P and K.
Accessing the economic value of manure begins by targeting fields low in P and K.
This report comes from UNL BeefWatch and Biological Systems Engineering at the University of Nebraska.