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  • Writer's pictureRachel Stevens

Long Term Tillage Through the Years

For the last 45 years, Purdue’s Department of Agronomy has carried on a study that is one for the record books. Started in 1975, a study continuously evaluating and documenting the impacts of four tillage types across three crop rotations has been grown on the Agronomy Research Center for Education. This long-term study has dramatic implications on how we understand long term environmental and economic impacts on tillage and crop rotations.

Since the study’s inception, four tillage practices, plow, chisel, ridge/strip till, and no-till, have been assessed across three different crop rotations, continuous corn, continuous soybeans, and standard corn/soybean rotation. This range of tillage and rotation has let researchers learn more about what combinations of crops work best with what tillage types as well as what practices are detrimental to yield and plant health.

It hasn’t been smooth sailing across all 45 years. In fact, any time someone notes, “we’ve had more variable weather the last 5 years”, they should really take a look at some of the dramatic weather patterns during the study. 1988 was so extraordinarily dry, with only 1.3 inches of rain during the first 10 weeks after planting, that corn yields came in as low 121 bushels/acre. A freeze on June 21st of 1992 dramatically reduced stand counts in across all treatments in the study. Growing season rainfall was 9 inches more than normal in 1993 and resulted in water logged soils and low yields.

Despite the trials across the years, we have had quite a few good years, and some interesting results during that time. Keeping with the changing traditions of Indiana producers has meant that some tillage practices have changed across the years. Initially, the four tillage types were chisel, plow, no-till, and ridge till. As ridge till fell out of popularity, strip till replaced that tillage practice in 2009. Additionally, changing management practices changed the way that tillage practices responded. Prior to the use of Roundup, the no-till treatments always had worse weed pressure, while the other tillage types used tillage to control weeds throughout the growing season. In 1995, Roundup was first used and helped even the playing field for the impact of weeds on each tillage type.

Other small changes made a big difference for various tillage types too. Prior to 1995, no-till planting had always occurred directly on top of the old row, making uniform seed depth and spacing very difficult. Trash wheels struggled to remove the old row, trash would hairpin in the rows, and the result was poor stand establishment. Starting in 1995, the no till planting was shifted six inches off the previous years row to get better stand establishment. Row spacing has changed across the years as well. Initially soybeans were planted in 30 inch rows, then switched to 7.5 inch rows in 1995, and finally switched back to 30 inch rows in 2005.

We are excited to share more of the interesting findings of our Long Term Tillage Study. We plan to feature articles on the impact of temperature and rainfall on yield by tillage type and rotation across the years, changes in soil characteristics over time, planting date impact on yield, as well as some posts detailing the changing management practices over the years.

We would like to direct your attention to our interactive corn yield results through the years. Select the rotations and tillage types you would like to view as well as the range of years. Statistics apply within rotation. (Push the full screen button to view all data options more clearly.)

What are you most looking forward to learning about the long term tillage research here at Purdue? We’d love to get your feedback on data analysis you are most interested in.

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