On-farm application of manure provides numerous benefits to soil by:
- Adding organic matter
- Improving structure and tilth
- Increasing water-holding capacity
- Helping soil resist compaction and crusting
- Providing plant-available nutrients to the soil
Nitrogen (N) is one decomposition product provided by manure. Evaluating organic N contribution from manure is important when making N management decisions.
Nitrogen from manure is in the form of ammonium from urine and organic N from solid waste. Ammonium is most easily taken up by plants but is quickly converted to nitrate as soils warm. Organic N is slowly released as plant-available N, primarily as nitrate, through the growing season. The availability of organic N depends on the source and form of manure and should be considered when evaluating N contribution for the crop. For example:
- Solid (i.e, feedlot) – 25% (year 1) and 15% (year 2)
- Stored liquid – 35% (year 1)
- Compost – 15% (year 1)
- Deep pit - 45% (year 1)
- Solid with litter – 30% (year 1)
- Solid without litter - 35% (year 1)
- Fresh – 50% (year 1)
- Stored Liquid – 35% (year 1)
A soil analysis will not credit N from manure. Therefore, knowledge of its contribution should be determined in addition to a soil fertility analysis. A manure analysis can provide information on the amount of organic N and ammonium per ton of manure. For example, for a manure analysis of 16 pounds of organic N per ton of cattle manure, only 25% of the organic N can be converted to a plant-available form in the first year after application and 15% in the second year after application. Therefore, 4 pounds of plant-available N can be contributed per ton of manure in the first year and 2.4 pounds in the second year after application. Ten tons of manure per acre would yield 40 pounds of plant-available N in the first year and 24 pounds the second year after application. These units should be added to any residual N from a soil analysis. A manure analysis is recommended to know rates of organic N available in manure being applied to a production field.
Clark, K. and Beegle, D. 2014. Nutrient management to improve nitrogen use efficiency and reduce environmental losses. Agronomy Facts 76. Penn State Extension. The Pennsylvania State University. https://extension.psu.edu.
Shober, A. L. 2015. Nitrogen cycling in agriculture. extension.org. University of Delaware.
Koelsch, R. 2018. Estimating nitrogen credit from manure. Drovers. https://www.drovers.com.
Web sources verified 8/25/19.
Performance may vary, from location to location and from year to year, as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible and should consider the impacts of these conditions on the grower’s fields.
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