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Manure characteristics

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What you need to know

Animal manures are a valuable source of nutrients for crop growth. But, since every farm operation is different, each manure will have unique characteristics. Make regular laboratory manure analysis an important step in your manure and nutrient management planning. Understand that the total nutrient content in manure is not available the first year and that some nutrients may be lost depending on management practices.

Nutrient content

Manure
Figure 1. Range of nutrient contents in different types of manures analyzed between 2012 and 2017. Manures followed by “S” are solid while manures followed by “L” are liquid.

Nutrients in manure are valuable resources, but not all manures are created equal. Manure nutrient content depends on many factors, including:

  • Animal species
  • Livestock diet
  • Livestock housing and bedding
  • Manure storage and handling system
  • Dilution from water (wash water or rain water)

Since these factors are different on each farm, the most reliable way to determine the nutrient content of manure is to collect a thorough sample and send 

it to a laboratory for analysis. Some people may use what we call “book values” (averages published by various organizations) to estimate the nutrient content in their manure, but we do not recommend this practice. For an example see Figure 1, which shows the range of nutrient content in select manure types. Small differences between the actual nutrient content of manure and the average “book value” can cause significant over- or under-application of nutrients that may affect crop yields and water quality. For tips on collecting a thorough manure sample, see Table 1.

 

Table 1. Tips for collecting a thorough manure sample before sending for laboratory analysis. Always use caution and proper safety measures while sampling manure.

Liquid and semi-solid manure

  • The best and safest time to sample liquid manure is after the pit or lagoon has been agitated and is being pumped out.
    • Collect 15 to 25 samples as the pit is pumped out from beginning to end. Dump into a 5-gallon bucket.
    • Mix the manure thoroughly.
    • Take a subsample, usually about a quart, and place in a plastic container.
    • Freeze the sample prior to sending to the lab.
  • Note: This method will not allow you to get the analysis results back prior to application for the current year. However, the analysis can be used to determine whether appropriate amounts of manure were applied to meet crop needs and for estimating the Year 2 and 3 nutrient credits.

Solid manure

  • Manure can be sampled from the stockpile or during hauling.
    • Stockpile:
      • Using a pitchfork or shovel, collect 15 to 25 samples from many different depths in the pile but avoid the crust.
    • During hauling:
      • Collect several subsamples from each load.
    • Place samples into a 5-gallon bucket and mix very well.
    • Take a subsample and place in a sealable plastic bag, then double up the bag.
  • Note: With the stockpile method, you may be able to have your manure analyzed prior to application. If sampling during hauling, you will not get the analysis results back prior to application for the current year. 

Nutrient Availability

Nutrients are not entirely available for crop use the first year after application. This is because nutrients can change forms, and only some of these forms are available for plants to use. When nutrients are bound to carbon they are in an organic form. If not bound to carbon, they are in an inorganic form. Typically, plants can only use the inorganic form of nutrients, but manure supplies both organic and inorganic forms. Microbes can break down organic forms of nutrients and mineralize them into inorganic forms. However, this can take several years and depends on soil moisture and temperature conditions (see Figure 2). 

nutrient cycling
Figure 2. A basic outline of nutrient cycling. Manure provides both organic and inorganic forms of nutrients, but plants can typically only use inorganic forms.
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Melissa Wilson, Extension manure management specialist

Reviewed in 2018

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