Laura Van Eerd, Katelyn Congreves, Adam Hayes, Anne Verhallen, and David Hooker. 2014. Long-term tillage and crop rotation effects on soil quality, organic carbon, and total nitrogen. Canadian Journal of Soil Science. doi:10.4141/cjss2013-093
Study Summary by Jordan Grigg

key messages

  • The inclusion of winter wheat in a crop rotation improved carbon and nitrogen storage
  • Soils that were not tilled held more carbon, nitrogen and scored higher on the Cornell Soil Health Assessment, compared to conventionally tilled soils

To till or not to till, if only there was an easy answer! Thankfully, a long-term research trial at the Ontario Crops Research Centre-Ridgetown can give us a place to start. For the past 25 years, this experiment has compared various levels of tillage treatments and crop rotations. In 2014 several researchers considered the impact of the treatments on soil organic carbon, total nitrogen and Cornell Soil Health Assessment (CSHA) score.  

Soil health takes into account the chemical, physical and biologic components of soil. Because of all of these dynamic components, it’s difficult to quantify soil health using one method. Soil organic carbon, total nitrogen and the CSHA score are a few of many measurement tools for soil health. Long-term trials can help to fill this gap in knowledge, especially when trying to measure the impact of best management practices. 

What they found

Soils that were not tilled stored more carbon, had high total nitrogen levels and scored higher on the soil health test, in comparison to the fields that were tilled. Four crop rotations were included in the experiment: (1) soybean-winter wheat, (2) soybean-winter wheat-corn, (3) continuous soybean, (4) soybean-corn. When winter wheat was included in the rotation, more carbon and nitrogen was stored. These soils also scored higher on the Cornell Soil Health Assessment. The positive effect of including winter wheat in the rotation was seen in both the conventional tillage and the no-till systems. Including winter wheat and a no-till system can improve soil health on southwestern Ontario farms.  

Soil organic carbon and total nitrogen are fairly universal measurements. They can be taken in any part of the world and interpreted the same way.  The CSHA was designed with a specific region in mind. The algorithm used to get the final soil health score was tailored to the soils and production system of the area it was developed in and using it outside of area it was developed may lead incorrect determination of soil health. This study suggests that the CSHA can be used and interpreted in southwestern Ontario.

Why it matters

The regional scale of this study allows us to create more specific and targeted plans to improve soil health. Soil health is one factor contributing to good crop yields. A healthy soil is better equipped to support crops than one with poor health. The variables measured in this study, soil organic carbon, total nitrogen and the CHSA score can all be used as indicators of soil health. The practice of no-till and including winter wheat in a diverse crop rotation may improve all three of these soil health indicators, soil health and crop yields in general in Southern Ontario. 

How they did it

This study took place on the long-term plots at the University of Guelph Ridgetown Campus, and was originally published in 2014. All on-site practices, such as fertilizer application, were chosen to mimic those that are typically used in Ontario. The Cornell Soil Health Assessment can be used as an indicator of soil health. The CSHA is a collection of 17 different analyses that cover the chemical, physical and biological properties of soil. The results from these 17 tests were used to calculate a final ‘Soil Health Score’ for the soil sample. A higher number indicates a healthier soil, and a lower number indicates a less healthy soil. Soil samples were taken at 15 and 120cm depth. These samples were analyzed for soil organic carbon and total nitrogen, to see if they were stored differently in the different treatments.  

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