Page 168 - Nutrient Management Planning Guide

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Manure Test Interpretation

Calculating Available Organic Nitrogen Content

An analysed sample of swine manure was found to contain 3.5 kg/1000 L total N and 1.8 kg/1000 L of NH

4

-N. The estimated organic N content in this manure is:

Organic N content = Total N – NH

4

-N

= 3.5 kg/1000 L – 1.8 kg/1000 L = 1.7 kg/1000 L

The amount of organic N that is expected to become crop available over the next three years is:

Available Organic N (year of application) = Organic N × 0.25 = 1.7 kg/1000 L × 0.25 = 0.425 kg/1000 L

Available Organic N (year 2) = Organic N × 0.12 = 1.7 kg/1000 L × 0.12 = 0.204 kg/1000 L

Available Organic N (year 3) = Organic N × 0.06 = 1.7 kg/1000 L × 0.06 = 0.102 kg/1000 L

Approximately 0.425 kg/1000 L of N will become available to the crop from the organic portion of the manure N in year of application (year 1). An additional 0.204 kg/1000 L of N will come avaialble to the crop in the first year after application (year 2) and 0.102 kg/1000 L of N will come available to a crop in the second year after application (year 3).

Manure NH

4

-N can be readily crop available, but is also at risk of being converted to ammonia (NH

3

) and lost via volatilization. Volatilization losses depend on manure placement, weather conditions during application, and

the elapsed time between application and incorporation. Table 4.3.4 provides NH

4

-N retention factors to correct total NH

4

-N for expected losses after application.