The answer is generally yes for many areas. If, however, diets, manure handling measures, and manure treatment are consistent throughout the year in areas where extremely cold temperatures do not occur (for example, an anaerobic lagoon in the southeast United States with consistent inputs and outputs), then only minor changes in manure nutrient concentrations may occur. On the other hand, variations in manure handling and storage, including changes in moisture content, or drastic changes in environmental conditions (temperature) can have a significant effect on manure nutrient concentrations.
Nitrogen is the nutrient that is the most dynamic. Changes in feed sources can also result in significant changes in manure nutrient concentration.
It is critical that all manure be sampled close to the time of land application to determine the nutrient content at the time of application. A new manure sample should be evaluated every time there is a change in these conditions:
- handling of manure,
- moisture contents, or
- feed sources for the animals.
Author: Karl Shaffer, Extension Associate for Soil Science, North Carolina State University
