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What is Manure Worth? Priceless

by 5m Editor
18 October 2012, at 12:00am

Manure accumulating on livestock farms has a positive economic value when replacing commercial fertilizer, according to Gerald May (Extension Educator) and Natalie Rector (Extension Nutrient Management) of Michigan State University (MSU) in the latest issue of 'MSU Pork Quarterly'.

Livestock farmers with manure management systems plans (MMSP) and who follow nutrient conservation practices should realise significant reductions in their 2012 fertiliser expenditures. Crop producers who utilise manure have likely already realized its value. Those crop farmers who are not managing manure to achieve its full potential may want to consider doing so. To ensure that manure's value is maximised, producers need to follow three basic, yet critical steps:

  1. Testing - soils and manure nutrient levels
  2. Crop uptake - apply manure on fields to maximise manure nutrient utilisation
  3. Conservation - maintain manure nutrients after application

Checking with a local Ag supplier, current prices for April 2012 for crop inputs were nitrogen (N) at $0.74/lb. (28 per cent liquid N at $415 per ton), phosphate (P2O5) at $0.56/lb. (11-52-0 at $715/ton) and potassium (K2O) at $0.52/lb. (0-0-62 at $645/ton). The same supplier admits the early 2012 spring has caught manufacturers short on N supplies and N prices are reacting to the shortage. Late December 2011, ammonia (NH3) was being booked ahead locally at $0.60/lb ($980 per ton). To compensate for a sensitive market, this article will use the 2011 price for N products.

Using these prices, Table 1 compares the 2012 nutrient value for two manure samples: Swine1, a low dry matter (DM) content liquid swine manure, and Swine2 a medium DM liquid swine manure. Swine1 and Swine2 are averages of 18 swine finishing barn samples collected by MSU Extension Pork Educators. The averages of these 18 samples show how different water conservation and management practices may relate to total volume and nutrient composition of the manure accumulated in the manure storage.

In Table 1, the N in swine manure makes the greatest contribution to the value of the manure, $14.76 for Swine1 and $24.90 for Swine2 both per 1,000 gallons. Nitrogen conservation practices play an important role in the agronomic value of swine manures. Fortunately, most swine manure is injected which conserves the majority of nitrogen in the manure.

Maximizing Crop Utilisation

The Tri-State Fertilizer Recommendations for Corn, Soybeans, Wheat and Alfalfa (Vitosh, Ext. Bulletin E-2567) suggest no additional P2O5 applications on fields testing over 40ppm P (80 lbs. P per acre). There are no agronomic reasons (no yield increase) for additional P2O5 applications. If manure is spread on fields testing over 40ppm P, the additional P2O5 should not be thought of as contributing to additional yield and building additional soil P reserves is not necessary. Additional P2O5 on fields testing over 40ppm P will have little or no short-term economic value.

Table 2 compares the swine samples described in Table 1 without credits for the P2O5, as if the manure had been spread on fields testing over 40ppm P. When either of these manures are applied on fields testing less than 40ppm P, at application rates providing 150 lb of N for growing corn, there is a dollar advantage over applying it on fields testing over 40ppm P.

In this example, the manure value per acre for Swine1 (at 6,100 gallons per acre) and Swine2 (at 3,600 gallons per acre) would be $50.40 and $30.74 more per acre, respectively, than if they are applied to a field testing less than 40ppm P.

Nitrogen Conservation

As previously discussed, N in manure makes significant contribution to the agronomic and economic value of manure. Available forms of N, (ammonia, nitrite, nitrate and nitrous oxide) are unstable and reactive in the environment. Application practices that disregard N's instability risk losing a significant portion of the N applied, thereby reducing the expected crop response and economic value of the manure to the cropping programme.

Ammonia N (NH3) is unstable and when left exposed on the soil surface will quickly volatise into the environment. Manure ammonia nitrogen losses in the four-day period after application, based on application method, as reported in Mid-west Plan Service (MWPS-18, 1998) are listed in Table 3.

Comparing the extreme N lost from broadcast application with no cultivation (25 per cent N lost) to the average losses of immediate cultivation or incorporation (three per cent N lost), the example Swine2 manure would lose 10.1 lbs. of N per 1,000 gallons, or 11 per cent of its value if it were broadcast and left on the soil surface.

Ammonia in manure is already in its ammonium form (NH4) but will be impacted by the same soil processes as commercial anhydrous ammonia (NH3), which is quickly converted to NH4 after application. NH4 carries a positive charge and quickly binds to the negatively charged soil particles. In cool soils, NH4 will remain stable in soils for long periods. As soils warm, bacterial processes convert the NH4 to the negatively charged nitrite and nitrate forms (NO2 and NO3). In cool soils (40 to 50°F), this conversion may make take up to 14 weeks but in warm soils (60 to 90°F), this conversion to NO2 and NO3 may take place in a few days.

While growing plants utilise NH4, NO2 and NO3, the negatively charged NO2 and NO3 no longer bind to soil particles and are therefore subject to leaching. The ammonia in manure applied in late summer or early fall may lose a high percentage of the N supplied as it leaches out the root zone before the next year's crop is even planted. Many farmers are currently evaluating cover crops and N stabilising products for their ability to retain N for the next year's crop.

To maximise the value from manure applications soil fertility levels, nutrient needs of the expected crop rotation, nutrients available from the manure and application timing need to be fully considered.

Transportation Costs

The economic value of manure is ultimately determined by what it cost the farmer to get it spread on the field. Application costs are determined by transportation distance and application method. In a 2011 Michigan Dairy Review article, Dr Tim Harrigan discussed the cost of manure transportation and differing transport methods (Harrigan, 2011). He reported the estimated cost for manure application with injection ranged from $0.0148 per gallon for fields within 2.5 miles of the source to $0.0191 per gallon for fields 4 miles from the source. Using Harrigan's estimates, Table 4 compares the impact application costs have on the manure value of the swine samples used in this article. Swine1 and Swine2 are compared based on each providing 150 lb N for the next crop.

Table 4 illustrates the importance of water conservation practices. As explained earlier, Swine1 and Swine2 are averages of 18 swine finishing barn samples collected by MSU Extension Pork Educators over the fall of 2008 and the spring of 2009. The nine farms represented by Swine1 had moisture contents over 97.5 per cent. The nine farms in Swine2 had moisture contents less than 97.5 per cent.

Diets and temperature impact a finishing pig's utilisation of water but the largest impact of water disappearance is the pig's ability to waste water. The nine farms represented in Swine2 were most likely using better water management and newer technologies than the nine farms represented in Swine1. The farmers represented by Swine2 were rewarded for their efforts by having a more nutrient rich product to apply to their fields and by having approximately 12 per cent less manure to haul on an annual basis.

For all species, water management plays an important role in the nutrient content and value of manure accumulating on livestock farms.

Table 4 also shows, within the transport distances represented, manure has a positive economic value when applied to fields where the nutrients will be fully utilised. Farmers generally choose between applying manure closer to the manure storage on fields where the nutrients will not be fully utilized versus hauling greater distances to fields needing the nutrients. Table 5 compares the value of Swine1 and Swine2 when applied to fields testing over 40ppm P within 2.5 miles of the source in comparison to hauling the manure farther distances (four miles) to fields where the nutrients will be fully utilised. The manures were applied at the same application rate as in Table 4.

In Table 5, Swine1 and Swine2 have positive economic value when applied to fields testing over 40ppm P within 2.5 miles of the source. But both manures have greater value when hauled farther distances and applied to fields where the nutrients will be fully utilised.

Conclusion

Manure accumulating on livestock farms has a positive economic value when replacing commercial fertiliser. Recognising its maximum value requires applying manure to fields where the nutrients will be fully utilized in the crop rotation and by using conservation practices that retain manure nutrients in the root zone for crop utilization. Manure value is enhanced by using water conserving practices and avoiding wasted and unnecessary water in the manure storage structure.

Resources

Harrigan T., 2011, Productivity and Economics of Nurse Tanks for Manure Transport. Michigan Dairy Review.

MWPS-18, 1998, Livestock Waste Facilities Handbook, Midwest Plan Service, Iowa State University, Ames, Iowa

Vitosh, M.L., J.W. Johnson and D.B. Mengel, Extension Bulletin E-2567, Tri-State Fertilizer Recommendations for Corn, Soybeans, Wheat and Alfalfa.

October 2012