Solid Manure Sampling for Nutrient Management Planning

Steps

1. Collect 10 quart-sized subsamples from various depths and locations in the manure pile and place them together in a bucket.
2. Mix the subsamples together thoroughly.
3. Place one pint-sized sample into a sampling container.
4. Place the labeled sample in a cooler and transfer to a freezer if you are not delivering it to the lab on the day it is collected

Manure is highly variable in composition and nutrient availability compared with commercial fertilizer, which has a guaranteed analysis. As reported in the publication Nutrient Characteristics of Solid Beef Manure in North Dakota, the nitrogen in solid beef manure in North Dakota ranges from 4 pounds/ton to 32 pounds/ton. Manure nutrient values depend on many things, including:

• Manure type
• Animal source
• Animal size
• Animal diet
• Bedding used
• Weather conditions
• Manure handling practices
• Storage systems

Accurate sampling and laboratory testing provides actual manure nutrient information. This information allows crop producers to strategize for maximum crop yields and minimal manure nutrient impact to the environment.

Contacting the laboratory you wish to send your sample to, before taking samples, is best. This is because each lab may have its own preferences for sample size, packaging, and delivery. Some labs will furnish sample containers and mailers free of charge.

Your local Extension agent can help you find a lab that is right for your needs.

If you have manure storage sites (stockpiles, compost, etc.) from multiple animal sources, take care to collect samples from these sites. Samples should be taken from each manure storage site that represents a different animal source, type, size, age, diet, management practice, and type of storage structure or other factor that could affect nutrient values.

To start the sampling process, collect 10 to 15 quart-sized subsamples using a spade or shovel from various locations and depths in the pile. Avoid sampling the dry top crust or other parts of the stockpile that may not be representative. Mix subsamples thoroughly in a bucket. Collect 1 to 2 pints and place in sealable plastic bag or a plastic bottle with a lid, or use the sampling containers the lab has provided you. 

This sampling procedure is consistent with analysis criteria stated in the USDA-NRCS North Dakota 590 Nutrient Management Standard.

Samples must be labeled before sending to the lab for analysis. Labeling with date, species, and location is a good practice (e.g. Fall 2019 beef stockpile). If collected during warm weather, the sample should be placed on ice, in a cooler, and delivered to the lab as soon as possible. If samples are going to be mailed, freeze immediately after collection. Send samples early in the week to avoid weekend layovers. Manure is constantly changing in physical, chemical, and biological characteristics. Keeping samples cool slows down the process of change and gives you a better snapshot of what is currently happening in the stockpiled manure.

When a manure sample is submitted for analysis you will need to tell the lab what nutrients you want analyzed. You can request almost any nutrient, as well as organic matter, pH, and electrical conductivity (salts). Total nitrogen (N), inorganic N, phosphorus (P) as P₂O_5, and potassium (K) as K₂O are the main nutrients you need to know for nutrient planning. Other nutrients such as sulfur and zinc may also be important for nutrient planning purposes. Total salt analysis may be useful if salts are a concern in the soil to which manure is to be applied.

Sample: Fall 2020 Beef stockpile
Type: Solid manure
Source: Beef
Storage: Stockpile
Lab number: LN652 

• ‘Sample’ is what you have named the sample in order to remember where it was taken from (e.g. bull pen vs. finishing steers vs. stockpile)
• ‘Type’ and ‘source’ describes what kind of manure and what species it was taken from.
• ‘Storage’ describes how the manure was stored when the sample was taken (e.g. stockpiled vs. composted vs. not piled)
• ‘Lab number’ is assigned by the lab and used if you ever have any questions about your manure report. You can call the lab that did the analysis and receive information by using this number.

Moisture 46
Dry Matter 54

These numbers are expressed as percentages (%). The moisture is the percent of water that was in the sample when it arrived at the lab. The dry matter (DM) is the percent of everything left (solids) after the sample is dried.
 

• Dry Basis: The percent of each element present in the manure sample; calculated after removal of moisture from the sample.
• As Received: The percent of each element present in the manure sample; calculated with no manipulation (drying) of the sample.  
• Lbs/ton: The total pounds of each element that is present in 1 ton (2000 lbs) of manure.

Manure test results should be reported “as is” or “as received” because that is the way manure will be land applied. If results are on a dry-matter basis, values can be multiplied by the manure dry-matter percentage (expressed as a decimal) to obtain the equivalent wet weight.

Example:

If total N = 2 percent dry basis and the sample is 60 percent dry matter, then N = 2 x 0.6 = 1.2 percent as is.

The nutrient content of the manure should be in the same units used in calibrating the land application equipment. For solid manure, typically pounds per ton is used. For solid manure spreader calibration procedures, see NDSU Extension publication NM-1418, “Manure Spreader Calibration for Nutrient Management Planning.”

Phosphorus should be reported as P₂O₅ because this is the value used in fertilizer application planning. If results are in elemental P, the conversion formula is: P x 2.29 = P₂O₅.

Potassium should be reported as K₂O because this is the value used in fertilizer application planning. If results are in elemental K, the conversion formula is: K x 1.20 = K₂O.

If results are given in percent, the following conversion factor can be used to get results in a more usable form: percent x 20 = pounds per ton. For example, in the table above, Total N is 1.00 as received x 20 = 20 lbs/ton or K₂O is 0.42 as received x 20 = 8.4 lbs/ton.

Using Tables 1 and 2 below, the crop-available portion of manure nutrients can be estimated. Manure nutrient analyses, combined with soil tests, previous crop credits and crop nutrient requirements, can be used to determine the proper application rate for manure. Determine crop nutrient requirements using NDSU Extension publication SF-882, “North Dakota Fertilizer Recommendation Tables and Equations.”  

Table 1. Nitrogen Availability and Loss as Affected by Method of Manure Application for Beef

Table 2. Phosphorus and Potassium Crop Availability for Beef Manure

Example

Using the North Dakota Corn N Calculator, it can be determined that for corn grown in Foster County under conventional tillage methods of medium-texture soils with historic yields > 160 bu/ac with 45 lbs/ac soil test N and soybean as the previous crop, you need 137 lbs N/ac. Knowing there is 20 lbs of N/ton from the manure analysis and that approximately 50% of the total N is available for crop production during year one, you would need to apply the manure at a rate of 13.7 tons/ac. Using NDSU SF-882, we know that if our soil test P is in the medium range (8-11 ppm) we need to add 52 lbs P₂0₅/ac and if soil test K is in the high range (121-160) then we need to add 60 lbs K₂O/ac. We know from our sample above that there are 7.9 lbs/ton P₂O₅ and 8.4 lbs/ton K₂O in the manure. Remember, 80% of the P and 90% of the K are available the first year for plant growth. So, if you’re spreading 13.7 tons/ac then you are applying 87 pounds of P/ac and 104 pounds of K/ac. Applying the manure from the sample above at a rate of 13.7 tons/ac meets/exceeds the necessary crop requirements.

If you have questions about manure analysis or nutrient management planning, please contact your local Extension office.

Reviewers:

Leslie Johnson, University of Nebraska-Lincoln Extension

Penny Nester, NDSU Extension Agent, Kidder County

Angie Johnson, NDSU Extension Agent, Steele County

The current author would like to extend appreciation to the previous authors for their contributions.