Using Liquid Manure to Top-Dress Wheat in Ohio

Liquid livestock manure can be applied to winter wheat as a replacement for top-dress fertilizer nitrogen sources such as urea or 28% urea ammonium nitrate (UAN). Late March or early April is generally the time of year in Ohio when the weather warms and the wheat crop emerges from winter dormancy, but supplemental nitrogen is required to maximize grain production.

When wheat is actively growing in March or April, fields can become firm enough to support manure-application equipment. This is when manure can be applied instead of commercial fertilizer to the growing wheat crop. Applying manure to wheat crops at this time of the year is an economical and environmentally sound way to utilize a byproduct of livestock production in an agronomic cropping system.

Swine Manure as a Top-dress Nitrogen Source for Wheat

Table 1 shows a research summary of three wheat top-dress treatments conducted over three years in Hoytville, located in northwest Ohio. All treatments received 120 pounds of nitrogen per acre. The results of the three-year study indicated that liquid swine-finishing manure, applied with a manure tanker, provided wheat yields similar to the yields realized after applying urea. The manure was applied with a 5,000-gallon manure tanker and Peecon toolbar. The urea was applied with a fertilizer buggy.

The surface-applied manure produced slightly better yields than the incorporated manure. In addition to swine-finishing manure, manure from sow-gestation barns and swine-nursery barns can also be good sources of spring fertilizer for wheat in Ohio. An accurate manure analysis is important to ensure that the proper amount of nitrogen is applied to maximize crop yields. A higher rate of manure would need to be applied to reach the desired pounds-per-acre of nitrogen as both swine-nursery manure and sow-gestation manure are typically lower in nitrogen when compared to swine-finishing manure.

The 2020 Tri-State Fertilizer Recommendations for Corn, Soybean, Wheat, and Alfalfa bulletin (extensionpubs.osu.edu/tri-state-fertilizer-recommendations-for-corn-soybean-wheat-and-alfalfa-pdf/),  recommends the application of 120 pounds of commercial nitrogen per acre if the yield goal is 100 bushels per acre. The nitrogen in swine manure is primarily in the ammonium form (NH₄), which is available to a growing crop. When using swine manure as a spring top-dress source for wheat, apply the same pounds of ammonium nitrogen in the manure as you would with pounds of nitrogen in commercial fertilizer. At this recommended rate, applying approximately 3,625 gallons per acre (based on the 33.1 pounds per thousand gallons of ammonium nitrogen amount from Table 2) of swine-finishing manure would accomplish the same goal. Do not count on any of the organic nitrogen becoming available in time for utilization by the wheat crop.

The nutrient balance of fertilizer in liquid livestock manure can be calculated using the information from Tables 2 and 3. If 3,625 gallons of manure were applied to a wheat field that yielded 100 bushels of wheat and one ton of straw, the nutrient contribution of P₂O₅ would be 58.4 pounds applied with the manure. The harvested wheat grain would remove 50 pounds of P₂O₅ per acre with an additional 3.7 pounds being removed with one ton of straw. In this example, the per-acre-input of P₂O₅ was 58.4 pounds per acre, and the removal total was 53.7 pounds per acre.

The Peecon toolbar (Figure1) used in this research project is similar to a grassland applicator in that it has narrow coulters that slice through the soil and boots to apply manure directly over the openings created. Benefits to subsurface manure application include lower potential for runoff, less risk of loss via volatilization, and less chance of the smell of manure lingering in the air. In addition, placing manure closer to the root zone allows the plants to take the manure up more quickly and utilize the nutrient more efficiently than if the manure is surface applied.

A drag hose is the most common method used to apply liquid manure to wheat in Ohio (Figure 2). When used on suitable fields, the drag hose alleviates soil compaction issues and is faster and more efficient than using a manure tanker. The drag hose travels across the wheat and causes very limited damage to the plants. Most of the damage to wheat fields occurs when the applicator turns at the ends of the field.  The weight of the tractor’s drag hose typically causes wheel tracks during these turns.

Liquid swine-finishing manure can also be surface-applied to wheat fields in the spring using a manure tanker. Given the weight of a full manure tanker and the moisture we typically expect in fields during late March and early April, soil compaction can be a concern. Manure tankers can work well on smaller fields, as well as fields where drag hoses are not suitable.

Manure application rates using manure tankers are similar to application rates used for drag hose applications. Just as the over-application of commercial nitrogen fertilizer will cause wheat to lodge and go down in a field, so will the over-application of liquid manure fertilizer.

Dairy Manure as a Top-dress Nitrogen Source for Wheat

The Ohio State University has also applied dairy-cattle manure as a spring top-dress to wheat in research plots, but grain yields were typically 12 to 15 bushels per acre less than yields obtained using commercial fertilizer. This may be due to dairy manure containing less total nitrogen and less of the available ammonium form of nitrogen—per 1,000 gallons—than liquid swine manure.

In recent years, dairy farms have successfully made applications of dairy manure to wheat fields intended to be harvested as wheat silage. Commercial manure applicators have used drop tubes to keep the manure off the leaf surfaces of the plants.

Any nitrogen remaining in the field after wheat silage harvest can be utilized by the silage corn crop that is usually planted immediately after a wheat crop.

When applying any manure to wheat in Ohio, you should always be aware of setback distances from ditches and streams. This information can be found in the NRCS 590 Nutrient Management Standard (agri.ohio.gov/wps/wcm/connect/gov/3dd2869c-32d2-4dd7-84d7-5c21f2f3b74b/590_OH_CPS_Nutrient_Management_2020.pdf?MOD=AJPERES&CONVERT_TO=url&CACHEID=ROOTWORKSPACE.Z18_M1HGGIK0N0JO00QO9DDDDM3000-3dd2869c-32d2-4dd7-84d7-5c21f2f3b74b-o3TOsXw). In addition to set-back distances, some areas in the state have weather-related restrictions that need to be followed. Contact your local Soil and Water Conservation District (SWCD) office about manure application restrictions specific to your county.

It is important to soil test regularly to keep soil nutrient levels in maintenance ranges. Excess phosphorus in the soil can cause nutrient loss and contribute to water quality issues, including harmful algal blooms. Consider the impacts of nutrient additions to waterways downstream when making decisions related to applying fertilizer.

Additional Resources

Ohio Composting and Manure Management, The Ohio State University
(ocamm.osu.edu/manure-management)

References

Culman, S., Fulford, A., Camberato, J., & Steinke, K. (2020). Tri-state fertilizer recommendations. Bulletin 974. The Ohio State University.
agcrops.osu.edu/FertilityResources/tri-state_info