Manure has value. That value may result from improvements in soil quality, increases in yield, and replacement of commercial nutrient required for crop production. Previous articles on manure’s value have focused on its soil health, environmental benefits and tools for estimating manure’s value. This article will focus on the economic benefits of manure. Key take-home messages include:
• Targeting fields requiring supplemental phosphorus (P) produces the largest economic value from manure.
• Targeting fields requiring supplemental potassium (K) significantly increases manure’s value.
• Additional value results from manure nitrogen (N) and micro-nutrients as well as from yield increases. However, these benefits are typically less important than P and K.
Nitrogen and phosphorus value
Manure is a supplemental source of P, organic-N, ammonium-N, and micro-nutrients commonly required by many fields. Cropland receiving surface-applied manure (not incorporated) benefits from both the 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. 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.
The nutrient replacement value of beef finisher manure from a beef barn with a deep pit for manure is approximately $24 per 1,000 gallons when injected in the soil. This assumes supplemental K is not needed and no yield increase. Approximately 35 percent 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). Thus, 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.
Potassium value
To further enhance the value of manure, targeting those fields that have a K 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.
Yield response
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 percent. Adding a percent 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 percent yield increase is achieved.
Similar benefits are observed for manures produced in other beef systems houses 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 discussed here, 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 leach beyond the root zone and be lost. See Determining Crop Available Nutrients from Manure (https://go.unl.edu/r7bx) for more information.
• Manure applied at rates near the crop’s N requirement typically over-apply 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 (see Nutrient Requirements for Agronomic Crops in Nebraska, https://go.unl.edu/vvmr, 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.
More information including graphics and assumptions for analysis is available online at http://newsroom.unl.edu/announce/beef/7388/42263. — Rick Koelsch, Biological Systems Engineering, University of Nebraska
