Manure spreaders are essential tools for distributing nutrients to crops to improve fertility and improve soil health. Therefore, achieving an even application of manure is just as important as with commercial fertilizers. Proper placement ensures that every part of a field receives the nutrients needed, leading to healthier crops and soil biology.

This guide explains how to use manure spreaders effectively.

Types of Solid Manure Spreaders

Horizontal Beater Spreaders drop manure from the back and break it up vertically. The spread pattern is limited in width, typically not much wider than the width of the spreader.

• Tips for Uniform Application:
  • Narrow the gap between passes to avoid uneven coverage.
  • Inspect the field visually after a few passes to ensure wheel tracks aren’t easily identified by manure gaps.
  • Note: These spreaders often apply heavier rates because wheel speed must increase to reduce application rates.

Vertical Beater Spreaders and Spreaders with Bottom Spinners are designed to throw manure both to the sides and back, resulting in a much wider spread pattern. Compared to horizontal beater spreaders, it is easier to achieve uniform coverage. This style spreader is ideal for lower application rates, drier manures, and sometimes commercial fertilizer products.

Side-slinger spreaders are designed to throw manure to one side.

• Spread pattern: Typically heaviest close to the spreader
• Often used for wetter solids, slurry manures, and sludge
• Tips for uniform application:
  • Narrow the gap between passes to avoid uneven coverage.
  • Inspect the field visually after a few passes to ensure wheel tracks aren’t easily identified by manure gaps.

Types of Liquid Manure Spreaders

Tanker-Style Spreaders typically have a tool bar for injection of manure below the soil surface, but they can also have splash fans or drop nozzle hoses for surface application.

Injection of liquid manure into soil is preferred over application to the soil surface because ammonium nitrogen in manure is not lost to the atmosphere as easily when manure is covered with soil. Injected manure is also more likely to stay in the field where crops can utilize it rather than being lost to surface waters via runoff if a precipitation event occurs soon after application. Liquid manure applied using a splash pan creates a recognizable “rooster tail” of manure, which tends to release more ammonia gas and creates more odor. Drop nozzles, on the other hand, allow for the placement of manure directly on the soil surface which helps reduce odor.

A drawback of liquid manure spreaders is the potential for soil compaction, especially with a full spreader, due to the weight of the applicator and manure. Manure tankers are much larger today than 20 years ago and fields need to be dry to handle this weight.

Handling manure in a liquid form brings the potential danger of manure gases, especially hydrogen sulfide.

Drag-hose spreaders are equipped with toolbars that surface-apply or inject manure, though the manure is pumped directly from the source to the implement through a long hose that is dragged behind the tractor rather than being carried in a tank wagon. These toolbars can be mounted on the tractor's 3-point hitch or pulled through the field. The weight of a drag hose filled with manure necessitates a large tractor with the necessary weights. 

Advantages of this style of manure applicator include:

• In-season application of manure is possible early in the growing season for some crops, such as corn, wheat, forages and cover crops.
• Variable rate application is possible by varying tractor speed.
• Application is much faster and more economical than using a tanker.
• Drag hoses can come directly from the manure pit or manure pond. The drag hose can also come directly off a frac tank filled by semi tankers.
• The size (diameter) of drag hoses has increased as larger tractors become available to pull the heavier hose. This allows for greater volumes of manure to be pumped and applied. Crossovers or manure bridges can be used to traverse roads or ditches, and booster pumps can help move manure through longer stretches of hose to further increase application efficiency.

Irrigation equipment can be used to apply manure that is primarily water, which typically comes from feedlot runoff holding ponds or the top layer of liquid in an anaerobic lagoon. However, sprinkler irrigation (i.e. pivots) must have appropriate nozzles to handle the solid particles in the manure. The big advantage of using irrigation equipment is that manure can be applied during the growing season when other liquid manure applicators cannot access the fields without damaging growing crops. This allows for application of manure when the crops need water and nutrients.

Big gun style irrigation equipment can also be used to apply manure with the big advantage being the ability to handle larger solid particles. However, a big disadvantage of big guns is the spray pattern which throws liquid manure into the air further, increasing potential odor problems for neighbors and losing larger portions of ammonium nitrogen.

Ensuring Even Application

To achieve an even spread with solid manure spreaders, follow these steps:

1. Field Inspection: Visually check the field for consistent manure distribution after several passes.
2. Use Calibration Tarps:
   1. Place one tarp directly in the spreader’s line of travel, ensuring the vehicle does not run over it.
   2. Position another tarp to the side to catch manure thrown laterally.
   3. Make a round or two with the spreader making sure the tarp catches any potential overlap, then weigh the manure collected on the tarps.

What to Look For:

• If the manure weights from both tarps are similar, the spread pattern is even.
• If the tarp to the side is lighter, reduce the spacing between passes and repeat the process.
• If the tarp to the side is heavier, increase the spacing between passes and repeat the process.

Bonus Tips:

• A 22-square-foot tarp provides an easy way to calculate application rates: the weight of manure on the tarp (in pounds) equals the application rate in (tons/acre).
• A small sample of manure collected from each of the tarps during calibration activities is ideal for sending in to a laboratory for nutrient analysis.

To calibrate liquid applicators with toolbars, use buckets under each knife and run the pump at the settings intended for application. Comparing the amount of manure collected in each bucket allows you to determine whether there are similar volumes of manure coming through each knife. If not, make adjustments.

• Verification of application rates for liquid spreaders is most frequently done using a flow meter; however, rain gauges can be used to verify irrigation equipment application rates. Be sure to use multiple gauges and average the results for the most accurate rate determination.
• When hauling slurry manure, agitation of the manure pit or earthen basic is needed to improve the consistency of the manure nutrients and ensure that solids are not allowed to build up in the bottom of the storage. When stirring or agitating a manure storage, be sure to adequately ventilate barns and anywhere people or animals might be. Be aware that hydrogen sulfide released during manure agitation is heavier than air, which can allow the dangerous gas to accumulate at ground-level if atmospheric conditions are right.

Importance of Maintenance

Proper maintenance of manure application equipment is important. When weather and soil conditions allow for manure application, properly maintained equipment is more likely to perform as expected and needed. Equipment breakdowns increase the opportunity for mishaps as people can get frustrated and take more chances when things don’t go right.

For liquid manure spreaders, uniformity depends heavily on the pump. Regular maintenance and monitoring are essential to ensure even application. Anytime the applicator toolbar deviates from being level, the distribution among discharge ports will be skewed with greater discharge from the “lower” ports and less discharge from the “higher” ports.

For solid manure spreaders, consistent operation and adjustments to spreader settings or driving patterns can greatly improve results.

For all manure spreaders, be sure to note what settings (gear and speed) are being used so when spreading multiple days or with different drivers, the spread pattern and rate stays consistent each day.

Conclusion

Manure spreaders are powerful tools for improving soil health and nourishing crops, but proper application techniques are vital for success. By using the right spreader, adjusting field passes, and verifying results with calibration, farmers can ensure their fields receive an even distribution of nutrients and organic matter. Thoughtful manure application not only benefits the current crop but also enhances soil biology for years to come.