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

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Crop Insights by Michael DeFelice, Paul Carter and Steven Mitchell

Summary

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.

Introduction

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.

Research on Corn Yields by Tillage

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 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.

**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.

A number of observations were collected during the analysis of the existing literature on tillage effects on soybean yield. Several studies indicated no-tillage yields improve after several years of continuous no-till have been in place. This time effect was thought to be the result of improved soil tilth over time in the no-tillage plots caused by increases in organic matter, soil enzyme activity, microbial biomass, and changes in soil porosity and aggregation. Drainage in new no-tillage plots is often poor until old tillage pans and lack of soil structure is corrected over time. Experiments conducted for a short number of years (less than 4 or 5) without prior years of no-tillage in the no-till plots probably do not provide a completely fair comparison to conventional tillage because the no-till soils have not had time to stabilize.

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 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.

The tillage regions outlined in this review do not have absolute or rigid boundaries. There are pockets of well-drained soils and local climate in the north where no-till works very well, and areas with poorly drained soils and local climate conditions in the south and west where no-till is more challenging. However, the general boundaries and trends are reasonably clear.

Over 40% of soybeans in the United States are now produced using no-tillage practices. It is apparent from this summary that a majority of the soybean producing regions of the U.S. would see a yield benefit or at least no yield reduction from no-tillage production. Even in the northern region the yield penalty to no-till soybeans is often more than out-weighed by the labor and fuel reductions and improvements in soil quality and conservation.

Corn Hybrids for No-till

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. Your Pioneer sales professional can help you determine the most suitable corn hybrids for your tillage and management conditions.

More Resources

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Conservation Tillage Information Center, 2004. National Crop Residue Management Survey – Conservation Tillage Data. West Lafayette, IN.
Cooper, M. and D.W. Podlich. 1999. Genotype x Environment interactions, selection response and heterosis. p. 81-92. In: J.G. Coors, and S. Pandey, (ed.), The genetics and exploitation of heterosis in crops, ASA-CSSA-SSSA, Madison, WI, USA. 524 p.
Cosper, H. R. 1983. Soil suitability for conservation tillage. J. Soil and Water Conserv. 37:152-155.
DeFelice, M.S., P. R. Carter, and S. B. Mitchell. 2006. Influence of Tillage on Soybean Yield in the United States and Canada. Crop Insights Vol. 16, No. 11. Pioneer Hi-Bred, Johnston, IA.
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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.