Study: Less Tillage and More Surface Residue Doesn’t Crimp Yields

An Upper Midwestern University Tillage Study Showed Yields Needn’t Be Sacrificed if Tillage is Sliced.

Tillage isn’t all bad. Proper tillage warms and dries the soil, kills weeds, incorporates fertilizers, and breaks up compacted layers. On the downside, tillage breaks apart soil aggregates, creating smaller-size particles that leads to soil erosion, crusting of the soil surface, hard pans, water-quality issues, and, over time, a decrease in soil organic matter. Below, Jodi DeJong-Hughes, University of Minnesota Extension Educator, sums up four years of university tillage research.

One hundred years ago, few choices of tillage tools existed. However, in the past 25 years, there has been an upsurge in the configurations of shanks, disks, and shovels that till the soil at different depths and aggressiveness levels.

These new tools impact soil warming and drying and may, ultimately, affect crop yield. Less tillage allows the soil to take in more intense rainfall before runoff begins, thereby, reducing soil loss. Advantages include:  

• Better economics   

• Less wear and tear on equipment   

• Better water-holding capacity of the soil  

• Improved biological populations and diversity in the soil 

However, concern about yield reductions due to cool and wet soil conditions may limit adoption of reduced-tillage systems for corn-soybean rotations on the poorly-drained soils that dominate much of western Minnesota and North Dakota.

Multistate Tillage Research 

To better understand these issues, a multistate effort involving University of Minnesota Extension, North Dakota State University (Aaron Daigh), and the Minnesota and North Dakota Corn and Soybean commodity groups set out to evaluate which tillage approach maximizes early-season soil warming and crop yields while, at the same time, improves soil health in the Red River Valley. The tillage systems included:

• Chisel plow

• Vertical tillag. 

• Strip-till with shank  

• Strip-till with coulters

In 2014, studies on two farms near Barney, North Dakota, and Fergus Falls, Minnesota, and a third in 2015 near Mooreton, North Dakota, were established. These farms ranged in soil series with sandy, loamy, and clayey textures, providing local farmers with a realistic picture of low-tillage impacts on their own acreage. Full-scale equipment was used in farmers’ fields.

Soil Moisture and Temperature Results

During each spring and early summer, the chisel-plow and strip-till berms consistently had the driest and warmest soil conditions (Figures 1 and 2). These were followed by the areas between the strip-till berms and vertical till. Finally, no-till had the wettest and coolest soil conditions. Differences due to soil types, most notably, these drying and warming differences among the tillage practices were greatest at the farm with sandy soils, moderate at the farm with loamy soils, and minimal at the farm with clayey soils (data not shown). As the surface of these clay soils dry, it is likely that moisture is more readily replaced by the capillary rise of deeper water than what would occur in the sandy soils. 

Figure one soil and moisture

Impacts on Plant Population, Growth and Yields
The trends in soil moisture and temperatures did not cause any differences in soybean or corn plant populations, growth, or yields.

Figure two soil type differences

Soybean yield was not affected by tillage at any of the farms during the four growing seasons, except on the farm with sandy soils near Barney in 2018 (Table 1). 

Table one

At that farm, both strip tills – with shanks or coulters – yielded 3.7 bushels per acre more on average than the chisel plowing and shallow vertical till. Yield difference trends were observed in corn in some years, but these differences were not consistent year-to-year, farm-to-farm, or among the tillage practices. Instead, benefits or consequences to corn yields were explained by whether timely fertilizer application and placement was done or whether soil conditions were too wet for proper tillage operations.

This data from this research shows that crop producers can do less tillage, leave more residue on the soil surface, while maintaining their yields. 

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