Subsurface Applying Swine Manure into Wheat as a Spring Nitrogen Source


In Ohio, the surface application of swine manure to soft red winter wheat in late March or early April is a common practice. This process makes good use of the ammonium nitrogen in the manure and provides an in-season window to apply manure to a growing crop. The savings in purchased nitrogen fertilizer can help offset most of the manure application expense.

The Maumee River in Northwest Ohio drains into the Western Lake Erie Basin and has been the ongoing focus of concern as phosphorus carried to the lake continues to be cited as a cause of harmful algal blooms. The surface application of manure, without follow up incorporation tillage, could be banned if water quality problems persist. This could jeopardize the application of manure to wheat and the application of manure to forages between cuttings. The purpose of this research project was to determine if manure could be subsurface applied to wheat using a Grassland Applicator toolbar and produce similar yields to surface applied manure or commercial fertilizer. If this method of manure application was successful, it could become a viable option for livestock farmers and commercial manure applicators wanting to apply manure to wheat in the Maumee River watershed.

Subsurface applied manure to wheat is not common practice in Ohio. Wheat plants and plant roots are damaged as the Grassland Applicator travels across the wheat field. This study sought to document yield losses if they occurred.

What Did We Do

This one-year study was designed to determine if manure could be subsurface applied to wheat and produce similar yields to surface applied manure or commercial fertilizer. Three livestock farmers with available wheat fields were contacted for on-farm manure plots. Each of the three farmers had slightly different comparison plots so we will refer to them as the Haselman Farm, the Maag farm, and the Leopold farm.

A 20-foot wide Grassland Applicator toolbar was attached to a 7,350 gallon manure tanker and used to subsurface apply manure to soft red winter wheat fields in early April. The manure tanker was owned by a commercial manure applicator and the livestock producers paid the commercial applicator for the manure application. The Grassland Applicator toolbar was owned by one of the livestock farmers.

The Haselman field compared subsurface applied manure to surface applied manure. Liquid swine finishing manure was both surface applied and subsurface applied in 40-foot (two 20-foot passes with the toolbar) treatments that were 1,050 feet long. Four treatments of subsurface applied manure were compared to four treatments of surface applied manure in a randomized block design. The surface application was accomplished by raising up the Grassland Application toolbar so that it just grazed the soil surface. This field was a certified organic field.

A history of manure samples showed 25 pounds of available nitrogen per 1,000 gallons in the swine finishing manure. The subsurface application involved slicing the soil every 7.5 inches to a width of approximately three eights of an inch and having a boot to place the manure over the soil opening. The soil slices were approximately three and a half inches deep. This field was organic and the wheat had been planted as a surface seeding and incorporated with shallow tillage the previous fall so there were no rows to follow. Due to the width of the dual tires on the application tractor and the flotation tires on the manure tanker, we estimated 40% of the wheat was flattened during the application process. The wheat was in the V4 stage of growth when the surface and subsurface manure treatments were applied. The field was harvested in early July using a John Deere combine with a 30-foot header.

On the Maag field, the subsurface manure treatment was compared to 100 pounds per acre of nitrogen applied as 28%Urea Ammonium Nitrate (UAN). On this field, the manure applicator traveled at a slight angle (approximately 10%) to the direction the wheat was planted to avoid having the toolbar follow the row. Both the manure and the 28%Urea Ammonium Nitrate treatments were applied the same day. As with the Haselman field, we estimated 40% of the wheat was flattened during the application process. This was the last of the three fields treated and the wheat was in the late V5 stage of growth due to weather delays and the commercial applicator having other manure application commitments. The 28% UAN was applied with an applicator with a 120 foot boom width.

The Leopold field involved wide-row wheat in a field that was transitioning into organic status. The wheat had been planted in twin rows that were five inches apart and left 22.5 inches for equipment to travel between the twin rows. The Grassland Application toolbar was connected to a smaller tractor and tanker with wheels designed to travel between the wheat rows. As a result, there was very little wheat run over and minimal plant damage from the application toolbar. Previous manure samples from this swine nursery indicated 17 pounds of available nitrogen per 1,000 gallons. The subsurface manure application rate was 6,000 gallons per acre to get 102 pounds of available nitrogen. This was compared to 6,000 gallons of surface applied manure.

Figure 1: Closeup view of the Grassland Applicator toolbar.


Figure 2: Manure application to V4 stage wheat.


Figure 3: V5 stage wheat flattened by the manure tanker. Soil slices are the Grassland Applicator toolbar.


Figure 4: Wide-row wheat with subsurface nursery manure application.

Manure samples were collected and analyzed during the application process.

Table 1. Average nutrient analysis of swine manure applied.
Swine Finishing Manure Swine Nursery Manure
Nutrient Pounds per 1,000 gallons Pounds per 1,000 gallons
Total Nitrogen 26.2 18.1
Ammonium Nitrogen (NH4) 24.4 16.5
Organic Nitrogen 1.2 1.0
Available Nitrogen 25.0 17.0
Phosphorus (P2O5) 7.1 4.3
Potash (K2O) 10.9 8.2

What Have We Learned

In the Haselman organic wheat field, the subsurface applied manure yielded less than the surface applied manure. The thought process is that the damage to the wheat plants and roots caused by the Grassland Applicator toolbar is responsible for this reduction. The wheat plants were in Feeks growth stage four and handled the tractor and tanker damage well. The tractor and manure tanker tracks through the field were visible but did not appear to cause much damage to the wheat.

In the Maag Farm where subsurface applied manure was compared to commercial fertilizer the subsurface applied yields were higher than the commercial fertilizer yields. This field was in Feekes growth stage five when the treatments occurred. The damage from the manure tanker tires was easy to see for over three weeks as plant growth was badly stunted. The size of the wheat heads in these tracks were much smaller than the undamaged areas of the field. Damage from the tractor tires seemed minimal even though the wheat was more advanced than we wanted.

In the Leopold field wide-row wheat plot, the incorporated manure outyielded the surface applied manure. The tractor tires and the Grassland Applicator toolbar caused minimal damage to the wheat plants. This field was also in Feekes growth four.


Table 2. Wheat yields for treatments comparing nitrogen applied as UAN at planting to side-dressed hog manure. Subscript letters a and b indicate yields that year were statistically different using ANOVA at 0.05 probability level.
Yield in Bushels per Acre
Treatments Haselman Farm Maag Farm Leopold Farm
Subsurface applied finishing manure 95.4 102.6
Surface applied swine finishing manure 93.2
28% Urea Ammonia Nitrate 96.9
Subsurface applied swine nursery manure 82.1
Surface applied swine nursery manure 79.3
Least Significant Difference (0.05) 3.35 13.95 7.33
Coefficient of Variability 1.01 3.99 3.99

The subsurface application of manure using the Grassland Applicator produced wheat yields statistically similar to surface applied manure in the Haselman field. The surface applied manure had less damage to the wheat plants due to the applicator coulters not cutting into the soil.

In the Maag field the subsurface applied manure produces slightly higher yields (although not statistically higher) to the commercial fertilizer. The damage to the wheat field was severe where the tires of the tanker all but killed the wheat plants. The wheat was almost to elongation (Feekes growth stage six) and this field was the most advanced of the three fields studied. The damage from the tractor tires was not severe but the plant damage from the extreme weight of the tanker tires was evident. There was a delay in getting the commercial manure applicator to the field and this resulted in the wheat being more advanced than planned. Wheat heads from plants in the tire tracks were half the size of those where just the tractor track traveled. Wheat heads from the manured treatments also appeared to be larger than the wheat heads from the commercial fertilizer treatments.

In the Leopold field the surface applied manure was slightly less than incorporated manure. Since there was minimal plant damage to the wide-row wheat from the toolbar or the tractor, incorporating the manure may have saved more of the nitrogen compared to the surface applied manure.

Rainfall in the area of the three research fields from April 1st to June 15th was measured at 6.86 inches. Field conditions were unusually dry during application time which helped reduce damage from the tractor and manure tanker tires.

Future Plans

In this study the subsurface application of liquid swine finishing manure and liquid swine nursery manure produced wheat yields similar to surface applied manure and commercial fertilizer. We intend to continue this study in 2022 and 2023 with these farmers to gather additional data.

To avoid the damage from the manure tanker tires, a more ideal situation would be to connect the Grassland Applicator tool bar to a drag hose. This would be a more efficient method to apply manure and cause less field damage and compaction. We also plan to use the toolbar to eventually apply manure to forages between cuttings.


Arnold, G., Field Specialist, Manure Nutrient Management Application, Ohio State University Extension

Additional Information

Sundermeier, A. (2010). Nutrient management with cover crops. Journal of the NACAA, 3(1). Retrieved from

Vitosh, M. L., Johnson, J. W., & Mengel, D. B. (2003). Tri-state Fertilizer Recommendations for Corn, Soybeans, Wheat and Alfalfa. Purdue Extension, Lafayette, IN.

Zhang, W., Wilson, R. S., Burnett, E., Irwin, E. G., & Martin, J. F. (2016). What motivates farmers to apply phosphorus at the “right” time? Survey evidence from the Western Lake Erie Basin. Journal of Great Lakes Research, 42(6), 1343–1356.

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