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1.- Total Kjeldahl Nitrogen (TKN) is the total amount of organic and ammonia nitrogen in the sample.
2.- Ammonia nitrogen (NH3) is the amount of inorganic nitrogen that is readily converted to plant available forms.
3.- Organic nitrogen is determined by the difference between total nitrogen and ammonia nitrogen.

Once the manure in storage has been well-agitated, the manure should be sampled for nutrient analysis. Once handling of manure begins, volatile gases such as ammonia are given off and the nutrient value of the nitrogen in the manure decreases. Therefore, it is important to anticipate how much of a certain nutrient will be lost before it can be utilized by the crop.


Volatilization of Ammonia

Volatilization of ammonia represents a significant cause of nitrogen loss. Loss of ammonia depends upon method of application and time before incorporation, as shown on the application chart for liquid manure:

Factors conducive to volatilization:

• high soil pH (>7.0);
  
• soils high in calcium carbonate (lime);
  
• soils with low retention ability for ammonium: e.g., low clay content, low organic matter, low cation exchange capacity;
  
• high soil or atmospheric temperature;
  
• liquid fertilizer applied onto dry soil;
  
• high wind velocity and/or highly aerated soils;
  
• high rate of fertilizer application;
  
• depth of incorporation/penetration < 2 cm.

Nitrate Leaching
Nitrate leaching is the form of nutrient loss that receives the most environmental concern. Leaching of nitrate-nitrogen occurs if excess nitrates are not utilized by the crop and are moved down the soil profile by infiltrating water.. If nitrates move out of the root zone, the nitrates are no longer available to the plant and eventually end up in the groundwater, where they may cause health problems in drinking water. Nitrogen fertilizers should be added to the soil only at rates that can be utilized by crops during a growing season. Nitrates should be present in the soil for the shortest possible time to minimize the likelihood of leaching. The Farm Practices Guidelines recommends no more than 150 lbs/ac of nitrate-nitrogen present in the top four feet of the soil profile and no more than 20 lbs/ac of nitrate in each subsequent foot of the soil profile.

Factors contributing to nitrate leaching to groundwater:

• coarse-textured or extensively cracked soils
  
• high concentration of nitrates in the soil profile due to excessive applications of nitrogen fertilizers, including manure
  
• significant precipitation to move nitrates downward
  
• limited plant root zone (due to plant species, time of year) to intercept nitrates
  
• groundwater table present (higher risk if closer to surface)
  
• use of irrigation

Not all of the above conditions must be met for nitrate leaching to occur.

To prevent nitrate leaching:

• Identify areas in the landscape where nitrate leaching into groundwater is most likely to occur (these are usually areas with coarse-textured soils and shallow water tables)
  
• Test soil every year. Manitoba's Farm Practices Guidelines recommends no more than 150 lb/ac of nitrate-nitrogen in the top four feet of the soil profile and no more than 20 lb/ac of nitrate-nitrogen in each subsequent foot of the profile. Refer to Appendix F, Monitoring Soil Nitrate, in Manitoba's Farm Practices Guidelines.
  
• Monitor groundwater levels and sample groundwater for nitrate content annually or when possible. Environmental guidelines have set 10 parts per million (ppm) as the maximum nitrate content for drinking water consumed by humans.
  
• Apply only as much nitrogen fertilizer to the crop that can be used in one growing season. Adjust commercial nitrogen fertilizer additions when manures have been applied.
  
• Minimize the window of opportunity for nitrate leaching. The time when nitrate is present in the soil to the time when it is utilized by the crop should be as short as possible. Spring applications are less risky than fall applications, and split applications of nitrogen during the growing season are less risky than applying all the nitrogen at the time of planting.
  
• If high levels of nitrate-nitrogen are found below four feet, use crops suited to your operation for retrieval of deep-leached nitrates.

Denitrification
Denitrification, like volatilization, can result in loss of fertilizer nitrogen. The difference between the processes is that volatilization occurs due to exposure to the atmosphere, whereas denitrification is loss of fertilizer nitrogen due to the absence of oxygen. The rate of denitrification decreases with depth and increases with temperature because it depends on biological activity.

Factors conducive to denitrification:

• soils with high organic matter (5 per cent or greater);
  
• limited oxygen, due to high water content, rapid respiration or compaction;
  
• neutral or alkaline pH (7.0 or greater);
  
• temperatures > 2oC;
  
• chemodenitrification (denitrification without microbial activity) requires low pH, but may be significant in freezing soils with high salt concentrations and high nitrite content.

To prevent denitrification:

• Avoid high applications of nitrogen to areas in the landscape with high water tables and intermittent ponding.
  
• Follow the same practices to prevent nitrate leaching.

Conclusion
The overall management practices to consider are:

• Incorporate manure as soon as possible.
  
• Test soil regularly to monitor nitrogen utilization and possible losses.

References
Tisdale, S. L., Nelson, W. L. and Beaton, J. D. 1985. Soil Fertility and Fertilizers. 4th ed. New York: Macmillan Publishing Company.

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