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Manure Sampling

Table 4.2.3 Advantages and Disadvantages of Sampling Manure Before or During Application

Parameter

Sampling Strategy

Sampling Prior to Application Sampling During Application

Timeliness of Test Results

; Manure test results can be used to calculate this year’s application rates.

: Cannot use analysis of samples collected during spreading to calculate this year’s application rate.

Accuracy of Analysis

: Manure tests may not be accurate or representative because manure is not thoroughly mixed.

; Manure tests will be more reliable because sub-samples can be collected as the manure is being applied, getting a more representative sample.

Difficulty in Collection

: Large equipment or agitation may be required to get a representative sample from manure storage.

; Minimal time required to sample during application.

Safety

: Sampling from storage facilities, especially lagoons or tanks, can be dangerous due to the risk of falling in or being overcome by gases (H

2

S and NH

3

).

; Sampling from application equipment reduces risk of falling in or being overcome by gases (H

2

S and NH

3

).

Sampling Strategy in Relation to Planning Application

Manure nutrient content and fertility recommendations are used to calculate manure application rates and additional fertilizer requirements. The benefit of manure sampling before application is the availability of test results to calculate application rates prior to application. The limitation is that the analysis may not be representative because the manure is not well mixed. An accurate analysis of manure nutrient content will yield a more reliable manure application rate.

When samples are collected during application, test results will not be available to calculate application rates for the current application. Rather, historical analyses (if available) or book values can be used to calculate the rate for the current application (Figure 4.2.2). When sampling during application, the current year’s analysis has two purposes:

Used to verify nutrient application rate and •

determine if additional fertilizer inputs are needed. Used to calculate manure application rates in •

subsequent years.

Three to five years of manure analyses should provide enough information to develop reliable estimates of average manure nutrient content for an operation. Historical analyses will provide a more representative manure nutrient profile to calculate manure application rates for a specific operation compared to book values. Once historical averages have been developed, there is less of a need for annual manure sampling. However, if any component of the animal management, manure storage or handling system substantially changes, new historical averages will need to be developed.