Influence of Tillage on Corn Yield in the United States and Canada¹

• An extensive literature review was conducted of corn research that compared yields of no-tillage to conventional fall tillage systems in the U.S. and Canada.
• The trial results were mapped by region to look for geographic and environmental patterns in the relative performance of no-tillage vs. conventional tillage on corn yield.
• The national average difference in corn yield between no-till and conventional tillage was found to be negligible with a 0.5% advantage to conventional tillage.
• No-till tended to have greater yields than conventional tillage in the south and west regions. The two tillage systems had similar yields in the central U.S., and no-till typically produced somewhat lower yields than conventional tillage in the northern U.S. and Canada.
• No-till had greater corn yields than conventional tillage on moderate- to well-drained soils, but slightly lower yields than conventional tillage on poorly drained soils.
• Corn yields tended to benefit more from no-till in crop rotation as compared to continuous cropping.
• Pioneer researchers have assigned a High Residue Suitability rating for all Pioneer® brand corn hybrids. The goal of this rating is to give customers guidance on selecting hybrids suitable for high residue tillage systems.

No-tillage crop production has been increasing in the United States for many years as growers seek to reduce input costs and labor and comply with government conservation programs. However, no-till corn has not increased at the same rate as no-till soybeans even though it has a longer history.

Many tillage studies have been conducted in the United States and Canada comparing corn yields under no-till vs. conventional tillage, but results often appear to be contradictory. This has only fueled the debate concerning the relative merits of no-till compared to conventional tillage over the years.

A general perception has arisen that no-tillage is more favorable in the southern United States, but does not perform as well in the northern United States or Canada. The previous Crop Insights showed that no-tilling soybeans resulted in either greater yields or no difference in yield compared to conventional tillage in almost 90% of the soybean producing area of the United States and Canada. So how does no-till corn compare to soybeans? This Crop Insights will present data to help determine if no-till has a different effect on corn grain yield than conventional fall tillage in different regions of the United States and Canada.

An extensive literature review of published research located 61 corn trials (representing 687 site-years of data) that compared corn yields by tillage system. All of the trials summarized used a close variant of a true no-tillage system with minimal surface disturbance only at planting and/or during fertilizer application. The conventional tillage systems varied from a maximum of fall moldboard plowing followed by multiple spring tillage passes to a minimum of fall chisel plowing followed by one or more spring tillage operations prior to planting. Strip tillage was not included because there were very few published studies on strip till, and the methods varied too widely to make valid comparisons.

These trials were then mapped to look for geographic and environmental patterns in the relative performance of no-tillage vs. conventional fall tillage on corn yield. An economic analysis was not attempted because many of the studies did not provide enough information for such an analysis, and because the economics of tillage vary by so many factors.

The national average difference in yield between no-tillage and conventional tillage corn was negligible with a small 0.5% yield advantage for conventional tillage (Table 1). However, the plot of corn experiment locations clearly shows regional differences in tillage effect on yield (Figure 1).

Table 1. Corn yield advantage of no-till over conventional tillage.

*Six corn studies were not used because data had been pooled
across rotations, or the rotation could not be determined from
the Materials and Methods.

(Click on the map to view a larger image) Figure 1. Corn yield advantage in no-till vs. conventional tillage by experiment location and region.

The data plot in Figure 1 was used to identify three areas where there appeared to be a different impact of no-tillage compared to conventional tillage on corn yield and these areas were overlaid on the map. These maps show that no-tillage tends to produce greater corn yields than conventional tillage in the southeastern, southern, and western United States (Table 1, Figure 1). A “transition zone” can be seen that extends from the northeastern United States through the northern Ohio valley and Missouri river valley where corn yields are generally the same in both tillage systems. No-tillage tends to have somewhat lower corn yields in the north central United States and Canada.

This data plot agrees with the general opinion that no-tillage corn performs better in the southern United States than in the north. However, this summary indicates no-tillage is equivalent in performance compared to conventional tillage into the central United States with only the most northerly areas of the Corn Belt showing a negative yield response to no-till. The yield advantage to no-till in the southeastern, southern, and western United States is quite substantial at about 12%. However, the yield disadvantage to no-till in the north-central U.S. and Canada is less at about 6%. The percent of total U.S. and Canadian corn acres in the southern/western, transition, and northern regions is 28, 28, and 42 percent respectively, with 2% of corn in the far west not mapped.

Soil drainage also had an effect on corn yield in no-tillage relative to conventional tillage (Table 1). As with soybeans, no-tillage had slightly greater corn yields than conventional tillage on moderate- to well-drained soils, but lower corn yields than conventional tillage on poorly drained soils. Sorting the data to show soil drainage by geography indicated this relationship was similar across all regions (Table 2).

Table 2. Interactions of soil drainage and crop rotation by geography on corn yield.

One repeated observation found in the literature was that no-tillage yields improve after several years of continuous no-tillage. This is thought to be the result of improved soil tilth over time due to increases in organic matter, soil enzyme activity, microbial biomass, and changes in soil porosity and aggregation in no-till plots. Drainage may also be improved in no-till plots over time as old tillage pans and lack of soil structure are eventually corrected.

As with soybeans, it seems clear from this summary that the most important factor governing the success or failure of no-till compared to conventional tillage is soil moisture. No-till clearly provides greater yields in the eastern, southern, and western United States where high temperatures, soils with low water-holding capacity, and/or unfavorable rainfall patterns often cause drought stress. No-till yields are equal or slightly less than conventional tillage in the northern United States and Canada where cold, wet spring conditions and poorly drained soils cause slower emergence and crop development in short maturity zones. This is why various methods of ridge-till and strip-tillage are being used in this region.

The tillage regions shown in Figure 1 are not absolute or rigid. In pockets with well-drained soils and favorable climate in the north, no-till works very well. Conversely, there are areas with poorly drained soils and local climate conditions in the south and west where no-till is more challenging. However, the map does accurately represent the general boundaries and trends.

About 20% of corn acres in the United States are currently produced using no-tillage practices. It is apparent from this summary that at least half of the corn-producing regions of the U.S. would see a yield benefit, or at least no reduction, by no-tillage production practices. It is clear from this analysis of both corn and soybean data that more soybean acres are in the positive to neutral yield category for no-till compared to corn. However, even in the northern region, there is only a small yield penalty to no-tillage corn production that is often out-weighed by labor and fuel reductions and improvements in soil quality and conservation. Further advances in various strip-tillage methods may enable even greater adoption of high residue corn production in the northern U.S. and Canada without any yield penalty.

University and private research indicates there is little effect of tillage on the yield potential of high-performing corn genetics. However, agronomic traits such as disease resistance or early season seedling vigor and emergence can cause some genetics to perform more poorly under high-residue no-tillage systems than under conventional tillage. Seedling emergence and development can be delayed in no-till compared to conventional tillage because spring soil temperatures tend to be lower and soil moisture levels tend to be higher under residue. A delay in seedling emergence often leads to postponement in vegetative growth, silking and grain dry-down. These delays can result in significant yield loss in shorter season growing areas, or where the relative maturity is long for the region.

The relative importance of crop traits for high residue cropping systems varies by geography or environmental factors such as soil drainage or frequency of drought stress. Excessive or deficient soil moisture appears to be a significant factor in the relative performance of no-till compared to conventional tillage. Soil moisture conservation and retention is a benefit for no-tillage under dry conditions and on moderate- to well-drained soils. However, wet springs and poorly drained soils tend to reduce yields in no-tillage compared to conventional tillage.

Pioneer provides a High Residue Suitability rating for each of its corn hybrids based on field observations and a weighted calculation of key trait scores that are important for high-residue growing conditions. You can read more about this rating in the Crop Insights article “High Residue Suitability Rating for Pioneer® brand Corn Hybrids” Vol. 15, No. 18. (www.pioneer.com/usa/agronomy/corn/management/high_residue.xml)

This rating is available in Pioneer seed catalogs and on the Pioneer GrowingPoint® website. Your Pioneer sales professional can help you determine the most suitable corn hybrids for your tillage and management conditions.

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Conservation Tillage Information Center, 2004. National Crop Residue Management Survey – Conservation Tillage Data. West Lafayette, IN.

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DeFelice, M.S., P. R. Carter, and S. B. Mitchell. 2006. Influence of Tillage on SoybeanYield in the United States and Canada. Crop Insights Vol. 16, No. 11. Pioneer Hi-Bred, Johnston, IA. (www.pioneer.com/usa/agronomy/soybeans/tillage_soybeanyield.xml)

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¹Note: This Crop Insights is based on the recently published journal article: DeFelice, M. S., P. R. Carter, and S. B. Mitchell. 2006. Influence of Tillage on Corn and Soybean Yield in the United States and Canada. Online. Crop Management. doi:10.1094/CM-2006-0626-01-RS. ©2006, PMN. (www.plantmanagementnetwork.org.)