Page 172 - Nutrient Management Planning Guide

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Manure Test Interpretation

Estimating Crop Available P

The total P content of a liquid manure sample is reported to be 1.1 kg/1000 L. The estimated amount of crop available P is:

Estimated Crop Available P (year of application)

= Total P × 0.7 = 1.1 kg/1000L × 0.7 = 0.77 kg/1000 L

Estimated Crop Available P (year 2) = Total P × 0.2 = 1.1 kg/1000L × 0.2 = 0.22 kg/1000 L

Estimated Crop Available P (year 3) = Total P × 0.06 = 1.1 kg/1000L × 0.06 = 0.07 kg/1000 L

Approximately 0.77 kg/1000 L of P will become available to the crop in year of application (year 1). An estimated additional 0.22 kg/1000 L of P will come available to the crop in the first year after application (year 2) and 0.07 kg/1000 L of P will come available to a crop in the second year after application (year 3).

Crop Available K

Unlike other nutrients, manure K exists exclusively in the crop available inorganic K + form. Research suggests that about 90% of manure K is effectively crop available:

Estimated Crop Available K = Total K × 0.9

Estimating Crop Available K

The total K content of a liquid manure sample is reported to be 1.7 kg/1000 L. The estimated amount of crop available K is:

Estimated CropAvailable K = Total K × 0.9 = 1.7 kg/1000 L × 0.9 = 1.53 kg/1000 L

Crop Availability of Other Nutrients in Manure

The crop availability of sulphur, calcium, magnesium and micronutrients is of less concern. When manure application rate is based on either N or P, other nutrients will likely be applied at rates several times higher than agronomic requirements, or what would be necessary to correct soil deficiencies.

Other Parameters

Manure tests may provide other information about the manure including pH and EC. Neither parameter has clear implications for manure application, since the relationship between manure and soil pH and EC are not well defined.