Making the most of manure

Posted on
September 21, 2020
Buffy Uglow    buffy_uglow@rockriverlab.com

By: Scott Fleming, Rock River Laboratory Nutrient Management Specialist

Manure is not a liability, it’s an asset.  As livestock and cash grain margins narrow for the foreseeable future, producers should start viewing manure with the rose-colored glasses it deserves. To best do this, producers should track exactly how much of this valuable asset is supplied to the crop to account for its tremendous value. Livestock owners should pay attention to three key factors that can affect the value gleaned from their manure: application rate, analysis, and placement.

Application Rate

The easiest means to harvest manure’s value requires little more than the manure applicators time. Unfortunately, accurate manure spreader calibration is not implemented on most farms. Whether applying liquid manure through a dragline, or pen pack solids via a box spreader, the only way to accurately credit manure application is by knowing the application rate.

When applying solid manure, the calibration process is fairly straight forward. The first step is weighing the application rig to determine the weight of manure hauled, explains Fleming. “Then calculate the area of manure application in acres. [Note: Area in acres is calculated by multiplying length by width in feet and dividing by 43,560.] It’s typically easier to calculate the manure rate for most dragline systems versus box spreaders. Custom haulers have a flow meter in their systems that calculates the manure application rate. Regulations state that flow meters must be calibrated twice per year as this allows for a very accurate estimate of manure rates. If a flow meter is not used, the same volume per area calculation can be used to determine the application rate but will be calculated in gallons per acre rather than tons.


Once the amount of manure to be applied has been established, it’s important to determine what is in the manure. A manure analysis is the best way to determine the fertilizer value of the manure. Proper sampling is critical to accurately reflect the true nutrient content of the manure.

When sampling solid manure, use a push-probe, auger, or spade to obtain a representative sample from several locations throughout the manure pile or pack. If the manure is being loaded for spreading, a sample can be obtained by subsampling several spreader loads. For liquid manure, we recommend thoroughly agitating the contents of the storage facility before sampling. It's best to make a composite sample from five to ten loads. The subsamples should be thoroughly mixed and submitted as one sample. 

Submitting a sample to the laboratory is as easy as placing the liquid or solid samples in a pint-size, screw-top plastic container filled to ¾ capacity and freezing immediately. Solid samples may also be placed in a high-quality freezer bag, but most laboratories have sample kits available so check with your laboratory or fertilizer supplier first to order sampling supplies. Then, keep the manure samples frozen until shipped or delivered to the laboratory. We advise customers to mail samples early in the week and avoid mailing over holidays and weekends. 

Most standard manure analysis includes moisture, total nitrogen (N), phosphorus (P), potassium (K), and sulfur (S). A comprehensive analysis will likely include the standard analysis specs, plus nitrate (NO3), ammonium (NH4), organic N, and pH. These values are expressed in either pounds per ton or pounds per 1000 gallons, and are multiplied by the application rate to determine the amount of nutrients applied.


The key to safe and effective manure application is applying the manure in the right place at the right time. “In many states, there are laws in place stating where and when manure may be applied. Even if your operation is not under a Nutrient Management Plan (NMP) it is in your best interest to follow these rules.

The rules he references exist to limit the amount of manure lost to the environment. When nutrients are lost to the environment they are no longer available to supply nutrients to your crop. In general, nutrients should not be applied during high runoff risk periods. The upper Midwest’s avoidance window is generally in February and March when snow is melting and precipitation rates are high.

Surface Water Quality Management Areas should also be spared from winter applications of nutrients. These are areas within 1000 feet of a lake or pond or 300 feet of a stream. Such areas close to water create a very high risk of runoff directly into the waterbody.

Soil type is the final factor to take into account when applying manure. Soil types that have high permeability or are seasonally wet are best reserved for spring manure application. Since these applications occur closer to the crop use timeline, the risk of loss is reduced. For more information on recommended application rates and timing, I recommend referring to the nutrient or manure application standards in your state.

With just a few simple, yet effective strategies, livestock producers can make the most of their manure. These fine-tuned approaches to manure application will allow for better use of the valuable fertilizer that is supplied via manure. By knowing how much, of what, and where to spread manure for optimal use, producers can make the most of manure applications during low and high margin years. After all, nutrient stewardship begins at the farm level.

Posted in:
Nutrient Management