Tillage and Rotation Impacts on Soil Quality

What can we learn about soil quality from long term tillage and rotation plots? Long term tillage plots were established by Doug Young and Tony Vyn at Ridgetown Campus, University of Guelph in 1991 on a Brookston clay loam soil. The tillage treatments initially consisted of moldboard plow, chisel plow, ridge till and two no-till treatments. The ridge till treatment was later converted to no-till. The plots are in a corn-soybean crop rotation.

Four years later, long term rotation plots were established by the same researchers at Ridgetown Campus in 1995 on a Brookston clay soil. Five rotations were studied including continuous corn, continuous soybeans, soybeans-winter wheat, corn-soybeans and corn-soybeans-winter wheat underseeded to red clover in moldboard and no-till. Each corn and wheat plot had several nitrogen rates applied.

Funding was received from the Canadian Agricultural Producers Addressing Environmental Issues program to take samples and to cover some of the costs of the soil analysis.

Earthworm Middens

Counts of earthworm middens were taken in the fall of 2006 from the mouldboard plow, chisel plow and no-till treatments of the tillage plots. Middens are piles of residue and soil found on the top of large earthworm burrows. The results in Table 1 show that the no-till had almost 6 times as many large earthworms as the moldboard and 3 times as many as the chisel plow.

Biological Activity

Bait lamina strips, were inserted into the same tillage treatments in November. Bait lamina strips were developed in Germany to give a measure of biological activity at depth but does not indicate what is eating the bait. The conditions at that time were cold and wet so there was less feeding than might have been expected. The no-till generally had more feeding than the moldboard or chisel treatments especially in the top 4 cm.

The picture shows the crop rotation plot. The soybeans in the foreground are continuous soybeans and the taller soybeans in front of the corn are in the corn-soybean-winter wheat rotation. Both are in the moldboard plow tillage system. The soil structure of the three crop rotation plot is also significantly better than the continuous soybean plot. 

Soil samples taken from selected treatments will be analyzed for organic carbon, nitrogen and phosphorus. Some other soil health measurements will be taken from the rotation plots this season. The yield data from all years of the tillage and rotation plots will be analyzed along with the soil data. 

Thanks to Ivan O'Halloran, Ridgetown Campus, University of Guelph and Ron Beyaert, Agriculture and Agri-Food Canada for their assistance with this project.

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