Economics of tillage

Study 1: Tillage and yield

Research by the University of Minnesota and North Dakota State University showed that reduced tillage systems increased crop residue cover and reduced soil erosion while having a minimal effect on crop yields. These results are often accompanied by lower tillage management costs (equipment, fuel and labor) compared to aggressive tillage systems.

On-farm research was conducted by University of Minnesota researchers from 2010 through 2012 in west-central Minnesota near Clarkfield. They compared four full-width tillage systems with varying crop residue levels in a corn-soybean rotation.

Tillage treatments

Tillage treatments included the following:

1. Strip-till (ST): A fall strip-till treatment consisting of fluted coulter and residue managers, followed by notched coulters that build a 3- to 4- inch berm.
2. Vertical-till (VT): Fall vertical-till pass plus a spring vertical-till pass. Either large wavy coulters or a gang of coulters operated at a less-than-4-degree angle.
3. Chisel plow/vertical-till (CP/VT) rotation: Fall chisel plow plus spring field cultivation before planting corn rotated with a fall vertical-till pass, plus a spring vertical-till pass system before planting soybeans.
4. Disk rip/chisel plow (DR/CP) rotation: Fall disk rip plus spring field cultivation before planting corn rotated with fall chisel plow, plus spring field cultivation before planting soybeans.

Results: Yield and residue levels

The study revealed corn and soybean yields weren’t affected by the type of tillage system, although tillage costs were substantially lower with strip till. However, the type of tillage did affect crop residue levels.

Strip-till retained the highest crop residue cover following both corn and soybean planting, while the chisel plow/vertical-till rotation had the lowest residue levels following corn and soybean planting (Figures 1 and 2).

Results: Costs and profitability

These data show Minnesota growers can increase profitability with reduced tillage (Table 1). In this study, costs per acre for a two-year corn and soybean rotation ranged from $29.20 for strip-till to $48.70 for fall disk rip and chisel plow rotation.

Strip-till saved $19.50 per acre over the DR/CP rotation with no loss in yield. By changing to strip-till, a farmer could save almost $20,000 for a two-year corn and soybean rotation on a 1,000-acre farm.

Study 2: Tillage and yield

Between 2005 and 2012, North Dakota State University conducted small plot tillage studies at three locations in North Dakota and one location in northwest Minnesota.

Results: Yield

Researchers found that 76 percent of the time, yield wasn’t affected by tillage when soybean followed corn (Figure 3).

In years when tillage type did affect soybean yield, strip-till had higher yields than chisel plow and no-till. In Carrington, when there was a yield difference, strip-till and no-till had higher yields than aggressive rototilling (Table 2).

*Chisel plow yields were statistically higher in one of the four years.
**Strip-till yields were statistically higher than chisel plow yields in three of the four years.

When tillage treatment has an effect

Results change slightly when growing corn following soybean or wheat. During 18 site-years, corn yield wasn’t affected by the type of tillage 44 percent of the time (Figure 4).

When tillage treatment had an effect, strip-till had higher corn yields than chisel plow and no-till 44 percent of the time. Chisel plow had higher corn yields than strip-till and no-till only 12 percent of the time. In other words, more aggressive tillage only increased yield about one out of every nine site-years.

Results by site

In Fargo, N.D., corn yield wasn’t affected by tillage method four out of the five years (Table 3). Tillage treatments at this site included chisel plow (two passes with a chisel plow and one field cultivation), strip-till and no tillage. The site was on a clay loam soil.

In Carrington, N.D., tillage treatments were aggressive tillage (two fall passes with a roto-tiller and two spring field cultivations), fall strip till, and no tillage on a loam soil in a wheat-corn-soybean rotation. There were no yield differences due to tillage over the five years of the study.

At sites in Prosper, N.D. and Moorhead, tillage treatments included chisel plow (fall chisel plow with a spring field cultivation) and strip-till. During four years at the two locations, strip-till had an average yield advantage of 14 bushels an acre (Table 3).

*Chisel plow yields were statistically higher than strip-till only in the study’s first year. For the following three years, strip-till yields were significantly higher than chisel plow yields.

Results: Profitability

If corn was priced at $3.30 a bushel, strip-till resulted in a profit increase of $46 an acre, while reducing the cost of additional tillage passes and maintaining more residue. Researchers surmised that, “the superior soil conditions may have facilitated greater rooting depth in the strip-till treatments and may have contributed to higher yields, especially in drier years”.

In a separate three-year study from 2006 to 2008 in southern Minnesota, University of Minnesota researchers compared soybean yields between chisel plowing plus spring field cultivation, strip-till and no-till for fields previously planted in strip-tilled corn.

Even with the higher residue levels, the type of tillage had no effect on the soybean yields during the three years (Figure 5). This demonstrates soybean adaptability among various tillage systems.

A University of Minnesota tillage study from 2008 to 2011 on poorly drained loam and clay loam soils at four sites (two located at research centers and two located in full-scale farm fields) in southwest and west-central Minnesota compared the effects of three tillage systems on continuous corn yields.

Tillage treatments included moldboard plow plus one or two spring field cultivations (MP), strip-till with a shank (ST), and chisel plow or disk rip plus spring field cultivation (CPDR).

Moldboard plow had the lowest residue levels averaged over the four locations at 13 percent (Figure 6). This residue level isn’t sufficient to protect the soil from wind and water erosion, and is the system with the highest fuel and time requirement of the three tillage treatments.

The chisel plow/disk rip tillage treatment had almost three times the residue level (37 percent) than moldboard plow. It’s considered adequate to protect the soil from erosion and maintain soil productivity over time. Strip-till had the highest level of residue in the continuous corn system at 61 percent soil coverage.

The continuous corn yields with fall strip-till were similar to moldboard plow during the first year but lower in the second and third years, except when a secondary spring strip-till pass was performed to manage the residue and warm the soil (Figures 7 to 10).

Residue in the reduced tillage systems tended to build up in years two and three, and covered the strip-till berm, creating a cooler environment for the seed. A second pass with a lighter, in-line coulter implement helped manage the residue and warmed up the soil similar to moldboard plow (Figure 11). Yields shown in figures 8, 9 and 10 demonstrate this effect.

In 2009, both Cannon City and Morris plots strip-tilled in the fall received a secondary in-line coulter pass in the spring. In 2010, only the Cannon City fall strip-till received the secondary pass in the spring. In 2011, both Cannon City and Morris again received a secondary pass in the spring.

When the second pass was added to strip-till, yields were statistically the same as moldboard plow and disk rip/chisel plow.

Choosing the best tillage system for your farm isn’t a “one-size-fits-all” decision. It’s similar to selecting hybrids to meet specific conditions and needs. It’s not necessary to leave the field completely covered with residue to improve soil health and reduce soil erosion while maintaining yields.

Evaluating the economics of tillage systems is very complex. Adjust tillage depth and intensity based on field factors such as

• Slope
• Soil texture
• Internal drainage
• Crop grown
• Previous crop residue remaining

Give consideration to

• The initial and maintenance costs of equipment
• The size of tractor needed to pull the tool
• Equipment depreciation
• Labor costs
• Conservation program incentives
• Increased management costs related to fertilizer and pest management

In addition, there are human factors that influence the choice of tillage system, such as farming and family tradition, age, commodity markets, government programs and neighbor perception.

When selecting a tillage system, it’s important to compare differences in production costs, as well as potential yield differences. Table 4 illustrates four typical tillage options when planting soybeans into corn residue in the upper Midwest, using the 2016 Iowa State University Custom Rate Survey.

One pass of tillage can cost $14 to $21 per acre depending on the implement. When planting soybeans, costs can range from $54.90 per acre for no tillage up to $85.15 per acre for chisel plow plus a spring field cultivation. This represents a $30 per acre difference. With soybeans at $9 per bushel, chisel-plowed fields would need a yield increase of more than 3 bushels per acre to pay for the tillage.

Fortunately, research has shown soybean yields are more consistent across soil conditions and tillage options. This makes no-till a viable and economical option.

Standing stalks in no-till and strip-till maintain more surface residue, which improves water infiltration and minimizes soil erosion. No-till and strip-till farmers that leave standing stalks also lower their harvest costs by not using a chopping head.

However, farmers who have high-residue systems frequently will have residue managers on their planter. This slightly increases the cost over conventional planters.

On the other hand, corn often needs incorporated fertilizers and seedbed preparation in the spring, which requires two to four additional field passes. This adds to the overall fuel costs, labor and wear and tear on equipment.

Table 5 uses four different tillage examples farmers may use when growing corn in the Upper Midwest, and the cost of each pass.

For a majority of the fields with chisel plow, disk rip or moldboard plow systems, fertilizer is broadcast in one pass and then incorporated with a secondary tillage pass in the spring. Strip-till saves a pass by applying phosphorus and potassium (nitrogen where appropriate) in the fall with the strip tiller. Plus, you can apply additional fertilizer with the planter and/or at side dress.

Using the 2016 Iowa State University Custom Rate Survey, strip-till costs $40 less per acre than moldboard plow with two field cultivations in the spring. If corn is priced at $3.30 a bushel, moldboard plow would need a yield increase of 12 bushels to pay for the extra tillage.

Chisel plow and disk rip with one pass of a spring field cultivation had similar rates and cost $25 more an acre than strip till, but $16 less an acre than moldboard plow. Even with the higher residue levels, Minnesota and North Dakota research data shows yields remain similar in a corn-soybean rotation regardless of tillage method.

In some regions, no-till is an option when growing corn, especially on sandier soils or in a rotation with very little residue from the previous crop. Fertilizer and lime are usually broadcast with no incorporation, and nitrogen may be side-dressed after the corn has emerged. The cost for no-till is just over $66 per acre, which is half the cost of the moldboard plow system.

*Strip-till price includes the cost of applying fertilizer with the strip tiller. In continuous corn, strip-till may need an additional lighter tillage pass in the spring to “freshen” the berm at a cost of $11.00 per acre.