Purpose
The forms of nitrogen contained in poultry litter are organic-N, ammonium-N, ammonia-N, and nitrate-N. One of the challenges in using poultry litter as a fertilizer substitute is making a good estimate of the plant available nitrogen (PAN). The value of PAN will depend on estimates of the amount of N that is lost to the air as ammonia following land application and the amount of organic-N that will be mineralized in the soil. The objectives of this workshop are to: (1) summarize organic-N mineralization data, (2) summarize the available data concerning ammonia loss following surface application of poultry litter, (3) review data concerning how fast ammonia is lost from a field to determine how quickly incorporation should be scheduled post-application, (4) provide means values from data to provide a practical guide for PAN calculations, and (5) compare the PAN estimates from the new method with current recommendation used by Clemson University Cooperative Extension.
What Did We Do?
Not all the nitrogen in poultry litter is available for plant use during the first growing season. The amount of N that can be used as a fertilizer substitute is the fraction of the organic-N (Org-N) that will be mineralized to ammonium-N following land application, the fraction of the ammonium-N (NH4-N) that is not lost as ammonia (NH3-N) and any nitrate-N (NO3-N) that is present in the litter. The recommended equation to estimate the plant available-N (PAN) is:
(1) PAN = mf Org-N + Af TAN + NO3-N (Evanylo, 2000; Chastain et al., 2001).
The amount of organic-N that will be mineralized depends on the organic-N content of the litter (lb Org-N/ton) and the mineralization factor, mf. The total ammoniacal-N (TAN) is usually reported on a litter analysis sheet as ammonium-N, but it is the sum of the ammonium-N and ammonia-N contained in the litter (TAN = NH4-N + NH3-N). It is the ammonia part of TAN that can be lost to the air following broadcast application of litter. Loss of PAN as volatilized ammonia is of concern because it represents a loss of N that may be used for plant production, and it contributes to air pollution. The amount of TAN that remains contributes to the estimate of PAN and is described by an availability factor, Af. The value of Af is the percentage of TAN lost as ammonia (AL) following application of litter is calculated as Af = 1 – (AL/100) where the value of AL is obtained from field measurements. Poultry litter generally only contains very small amounts of nitrate-N (1 to 5 lb NO3-N/ton) and all of it counts toward PAN.
Several publications have reported measurements of the mineralization factor, mf, for a variety of manure types. A summary of the literature was provided by Evanylo (2000) and the practical range of values for poultry litter are compared with other types of manure in Table 1. In South Carolina, an mf of 0.60 has shown to work well in practice. However, in cooler climates the best value may be 0.50 since low soil temperatures generally slow the mineralization rate. Other factors such as soil pH, and moisture content can result in variation in the amount of organic-N that will actually be mineralized in a particular field. The values shown in the table are good recommendations for practical use unless a better value is available for a particular state or region. Some organizations (e.g. Clemson University Extension) use a single value of mf for manure from all types of animals. However, the available data indicates that the value of mf to be used in equation 1 should vary with animal type.
Table 1. Mineralization factors (mf) for common types of animal manure (Evanylo, 2000; Chastain et al., 2001).
| Recommended mineralization factors | |
| Poultry | 0.60 (0.50 to 0.70) |
| Swine | 0.45 (0.40 to 0.50) |
| Dairy | 0.35 (0.25 to 0.35) |
| Beef | 0.40 (0.30 to 0.45) |
Several studies and literature reviews provided data concerning the maximum amount of ammonia that was lost after applying poultry litter to hay or ryegrass fields (Lockyer et al., 1989; Marshall et al., 1998; Meisinger and Jokela, 2000; Nathan and Malzer, 1994; Montes, 2002). The theory and data contained in these publications indicated that the amount of ammonia that was lost from surface applied broiler and turkey litter was influenced by the pH of the litter, the pH of the soil or residue that was on the field at time of application, and the temperature. In general, it was shown that if the litter was applied to residue with a high pH (8+) the amount of ammonia lost following broadcast application was increased and if the pH of the residue was low (about 5, Montes, 2002) the amount of ammonia lost decreased. The air temperature on the day of application also influenced the amount of ammonia that was lost with an increase in temperature from 68 degrees to 85 degrees causing an increase in ammonia loss by a factor of about 2. The average maximum ammonia loss (AL) following broadcast of bedded poultry litter to a mowed grass field was determined to be 37% (n = 6, coefficient of variation = ± 19.7%) with a 95% confidence interval that ranged from 29% to 44%. Much less data was available concerning the amount of ammonia lost after application of bedding-free poultry litter. This type of litter is removed from high-rise layer buildings, manure below the roost areas in broiler breeder barns, and un-bedded litter removed from some broiler barns. The data indicated that less ammonia was lost as compared to bedded litter due to the lower pH of the material. The recommended estimate of AL for un-bedded litter is 28%. Therefore, the recommended values for Af to be used in equation 1 for broadcast application of litter during the cooler weather of spring and fall is 0.63 for bedded poultry litter (most broiler and turkey barns) and 0.72 for un-bedded litter. If litter is applied during summer, which is not common, the AL values were doubled based on theory and practical measurements and gave a summertime Af value of 0.26 for bedded litter and a summertime Af value of 0.44 for un-bedded litter.
A common recommendation to reduce ammonia loss after spreading poultry litter, or granular N fertilizer, is to incorporate the litter into the soil with a disk harrow on the same day or provide irrigation of more than 0.25 inches of water. Light disking has been shown to reduce ammonia loss significantly (Chastain et al., 2001; Pote and Meisinger, 2014). The resulting value of Af that has been recommended for use is 0.80 if litter is incorporated on the same day that it was spread. The key question is how much time can lapse between spreading litter and incorporation to get an Af of 0.80? The measurements provided by Montes (Montes, 2002; Montes and Chastain, 2005) indicated that 98% of the total ammonia loss occurred 24 hours after application and 70% of the total had already been lost to the air after 8 hours. The results provided by Montes along with the average maximum ammonia loss values from the literature were combined to provide the recommended Af values given in Table 2. These results indicate that if the goal of incorporation is to yield an Af of 0.80 the litter must be incorporated within 2 to 8 depending on the season of the year and whether the litter contained bedding.
Table 2. Recommended TAN availability factors, Af, for application of poultry litter with and without incorporation.
| Bedded Litter | Un-Bedded Litter | |||
| Spring and Fall | Summer | Spring and Fall | Summer | |
| Af | Af | Af | Af | |
| Broadcast – no incorporation | 0.63 | 0.26 | 0.72 | 0.44 |
| Time lapse before incorporation | ||||
| 1 hour | 0.95 | 0.90 | 0.96 | 0.92 |
| 2 hours | 0.90 | 0.81 | 0.93 | 0.85 |
| 3 hours | 0.87 | 0.73 | 0.90 | 0.80 |
| 4 hours | 0.83 | 0.67 | 0.87 | 0.75 |
| 6 hours | 0.78 | 0.56 | 0.83 | 0.67 |
| 8 hours | 0.74 | 0.48 | 0.80 | 0.61 |
What Have We Learned?
The impact of the method to estimate PAN using the Af values developed from the literature (Table 2) is best demonstrated by a practical example using nitrogen concentrations obtained from a broiler barn with bedded litter. The nitrogen contents and the estimates of PAN based on the current Clemson Extension recommendation and the PAN estimates using the new information are compared in Table 3. For this litter analysis, the PAN estimate using the new recommendation was 6% larger indicating a small increase in useful N. It was assumed that the litter application rate would be based on an agronomic rate of 100 lb N/ac. The calculated application rates were rounded to the nearest ton/ac and gave 3 tons of litter per ac in both cases. The estimate of ammonia emissions per 100 acres was decreased from 1650 lb NO3-N/ac using the old values to 1221 lb NO3-N/ac based on the mean Af from the available data. These results indicate that the current Clemson Extension recommendations are under predicting the amount of PAN that could be used as an N-fertilizer substitute. The more significant impact is that the current recommendations over predict ammonia-N emissions by 26%.
Table 3. Comparison of the PAN estimates and the ammonia-N emissions per 100 acres using the current Clemson Extension recommendations and the new values of Af based on a review of the literature. The calculations are for bedded broiler litter that contains 42 lb Org-N/ton, 11 lb TAN/ton, 1.4 lb NO3-N/ton and spread to provide 100 lb of N/acre. Both litter application rates rounded to 3.0 tons/acre.
| Clemson Extension Recommendation | New Recommendation Based on Tables 1 & 2 | |
| mf | 0.60 | 0.60 |
| Af | 0.50 | 0.63 |
| PAN estimate (equation 1) – lb PAN/ton | 32 | 34 |
| Percent difference | +6% | |
| Litter Application Rate – tons/acre | 3.0 | 3.0 |
| Ammonia loss – lb NH3-N/100 ac | 1650 | 1221 |
| Percent difference | (-26%) |
Future Plans
The immediate plans are to use these results to provide a more realistic estimate of PAN and ammonia emissions for poultry litter in South Carolina. These results can also be used by Extension Educators in other states and regions to revise estimates of PAN for their conditions. The method presented in this paper can also be used in the future as better estimates of mf and Af are empirically determined.
Authors
Presenting & corresponding author
John P. Chastain, Professor and Extension Agricultural Engineer, Clemson University, jchstn@clemson.edu
Additional Information
Chastain, J.P., J.J. Camberato, and P. Skewes. 2001. Poultry Manure Production and Nutrient Content. Chapter 3B in Confined Animal Manure Managers Certification Program Manual: Poultry Version, Clemson University Extension, Clemson SC, pp 3b-1 to 3b-17. https://www.clemson.edu/extension/camm/manuals/poultry/pch3b_00.pdf.
Evanylo, P.G. 2000. Organic Nitrogen Decay Rates. In: Managing Nutrients and Pathogens from Animal Agriculture (NRAES-130). 319-333. Ithaca, NY: NREAS, Cooperative Extension, Cornell University.
Lockyer, D., B. F. Pain, J. V. Klarenbeek. 1989. Ammonia Emissions from Cattle, Pig and Poultry Wastes Applied to Pasture. Environmental Pollution 56:19-30.
Marshall, S.B., C. W. Wood, L. C. Braun, M. L. Cabrera, M. D. Mullen, E. A. Guertal. 1998. Ammonia Volatilization from Tall Fescue Pastures Fertilized with Broiler Litter. Journal of Environmental Quality 27(5): 1125-1129.
Meisinger, J.J., W.E. Jokela. 2000. Ammonia Volatilization from Dairy and Poultry Manure. In: Managing Nutrients and Pathogens from Animal Agriculture (NRAES-130). 334-354. Ithaca, NY: NREAS, Cooperative Extension, Cornell University.
Nathan, M.V., G. L. Malzer. 1994. Dynamics of Ammonia Volatilization from Turkey Manure and Urea Applied to Soil. Journal of Environmental Quality 58(3): 985-990.
Montes, F. 2002. Ammonia Volatilization Resulting from Application of Liquid Swine Manure and Turkey Litter in Commercial Pine Plantations. MS Thesis, Clemson University, Clemson, SC.
Montes, F., J.P. Chastain, 2005. Ammonia Volatilization from Turkey Litter Application in a Pine Plantation in South Carolina. ASAE Paper No. 054077, St. Joesph, Mich.: ASABE.
Pote, D., J.J. Meisinger. 2014. Effect of Poultry Litter Application Method on Ammonia Volatilization from a Conservation Tillage System. Journal of Soil and Water Conservation 69(1):17-25.
Acknowledgements
This work was supported by the Confined Animal Manure Managers (CAMM) Program of Clemson University Extension.
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