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Chapter 6.1

Estimate Available Nutrient Content of Manure

Chapter 4.2 described techniques for manure sampling. Once the results of the manure analysis are available the amount of crop available nutrients in the manure can be calculated, as illustrated in Chapter 4.3. Crop available nutrient content is a main factor that will influence manure application rate calculations.

Crop Available Nutrient Calculations »

Several equations used to estimate crop available nutrient content of manure, originally presented in Chapter 4.3, are presented here for reference purposes. For a more detailed discussion of estimating crop available nutrient content refer to Chapter 4.3.

Crop Available N Calculations

Organic N = Total N – NH

4

-N

Available Organic N (year 1) = Organic N × 0.25

Available Organic N (year 2) = Organic N × 0.12

Available Organic N (year 3) = Organic N × 0.06

Retained NH

4

-N =NH

4

-N × Retention Factor (Table 4.3.4)

Estimated Crop Available N = Available Organic N (year 1) + Retained NH

4

-N

Crop Available P Calculations:

Estimated Crop-Available P (year 1) = Total P × 0.7

Estimated Crop-Available P (year 2) = Total P × 0.2

Estimated Crop-Available P (year 3) = Total P × 0.06

Crop-Available K Calculations:

Estimated Crop-Available K = Total K × 0.9

Crop Availability of Other Nutrients in Manure

There is little need to be concerned about the crop availability of Ca, Mg and micronutrients (e.g., iron, zinc, copper) in manure. In Alberta soils deficient in nutrients other than N, P, K are rare, particularly if a field has received manure in recent memory. Also due to the balance (or imbalance) of nutrients in manure, if application rate is based on either N or P, all other nutrients will likely be applied at rates several times higher than agronomic requirements.