Page 167 - Nutrient Management Planning Guide

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Chapter 4.3

Table 4.3.3 Conversions for Units Commonly Appearing on Manure Test Reports

Starting Unit Multiply By Desired Unit

Solid Manure

% 10 kg/t % 20 lb/tn kg/t 2 lb/tn mg/kg 0.001 kg/t g/kg 1 kg/t t/ha 0.4461 tn/ac

Liquid Manure

% 10 kg/m 3

kg/m 3 1 kg/1000 L % 100 lb/1000 gal kg/1000 L 10 lb/1000 gal mg/L 0.001 kg/1000 L g/L 1 kg/1000 L ppm 1 mg/kg and mg/L L/ha 0.089 gal/ac

Estimating Available Nutrient Content

Laboratory results will typically include measurements of total N, ammonium N (NH

4

-N), total P and total K. Generally there is little nitrate NO

3

-N in raw manure; therefore, there is no value to requesting this analysis. However, NO

3

-N is present in composted manure and therefore a nitrate analysis should be requested. In order for these measures to be useful for nutrient management planning, the availability of each must be considered. Since a significant proportion of many nutrients are in organic forms not immediately available to the crop, estimating crop availability represents a real challenge. Manure application rate should be based on estimated available nutrient content.

Crop Available N

Crop available N estimates the amount of total manure N that could be available for crop use in the year of application. For this estimate, manure test results along with manure application method and timing can be used. Most labs provide measures of total and ammonium N (NH

4

-N). The difference of these two parameters provides an estimate of organic N in the manure:

Organic N = Total N – NH

4

-N

Although mineralization of organic N is controlled by soil moisture and temperature conditions, it is safe to assume that 25% of organic N will be mineralized to crop-available forms in the year following application:

Available Organic N = Organic N × 0.25 (year of application)

Additional organic N will be mineralized in subsequent years and can be estimated when planning future manure applications.

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

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