Four years of tillage research wraps-up

by Jodi DeJong-Hughes

Different variations of tillage have been practiced since the beginning of agriculture.  Proper tillage warms and dries the soil, kills weeds, incorporates fertilizers, and breaks up compacted layers.  On the down side, tillage breaks apart soil aggregates, creating smaller-sized 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.

Different variations of tillage have been practiced since the beginning of agriculture.  Proper tillage warms and dries the soil, kills weeds, incorporates fertilizers, and breaks up compacted layers.  On the down side, tillage breaks apart soil aggregates, creating smaller-sized 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.

One hundred years ago, there were few choices of tillage tools.  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.   These new tools impact soil warming and drying and may ultimately affect crop yield.

To address these issues, a multi-state effort, involving University of Minnesota Extension, North Dakota State University (Dr. Aaron Daigh), and the Minnesota and North Dakota Corn and Soybean commodity groups set out to evaluate which tillage approach (chisel plow, vertical tillage, strip till with shank, and strip till with coulters) maximizes early-season soil warming and crop yields while at the same time improving soil health in the Red River Valley. 

Less tillage on cropland allows the soil to take in more intense rainfall before runoff begins, thereby reducing soil loss.  Advantages to the crop producer include better economics, less wear and tear on equipment, better water holding capacity of the soil, and 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. 

In 2014 two farms near Barney, ND and Fergus Falls, MN, and a third farm in 2015 near Mooreton, ND 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.

During each spring and early summer, the chisel plow and strip-till berms consistently had the driest and warmest soil conditions followed by the areas between the strip-till berms and then the vertical till as the wettest and coolest soil conditions (see figures below).  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. 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 occurs in the sandy soils. 

The trends in soil moisture and temperatures did not cause any differences in soybean or corn plant populations, growth, or yields. Soybean yield was not affected by tillage at any of the farms during the past four growing seasons, except on the farm with sandy soils in 2018 (see table below). At that farm, both strip tills yielded 3.7 bushels per acre more than either chisel plowing or the shallow vertical till. Yield differences were observed in corn during 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, and not affect their yields.

 

temps

 Soil temperatures for four tillage systems averaged across the three farm locations taken on the first day of planting in May.

 

soil

Soil moisture content for four tillage systems averaged across three farm locations taken on the first day of planting in May.



crops

Corn and soybean yield data for two locations from 2015-2018. Red and blue circles indicates a difference in yield due to tillage