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Solid manure sampling

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

Why sample manure?
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 four 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.

How should solid manure be sampled?
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.

How should manure samples be handled?
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.

What to analyze?
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 P2O5, 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.

How can manure analyses be used?
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.

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 percent 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 percent of the P and 90 percent 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. •

Mary Keena is a livestock environmental management extension specialist at the Carrington Research Extension Center. This article was originally published by North Dakota State University. For the full article including sample manure nutrient estimates, visit: https://www.ndsu.edu/agriculture/extension/publications/solid-manure-sampling-nutrient-management-planning.

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