Benefits of non-inversion systems sometimes overestimated

Established to compare and contrast the performance of conventional tillage versus minimum tillage systems, results of a 23 year study from Knockbeg, Co. Carlow were shared with delegates at this year’s Teagasc National Tillage Conference, today, January 29.

Spearheading this work and sharing some of its key findings was Dermot Forristal, a Teagasc Research Officer, who prefaced why the experiment was established.

“Back in the early 2000s, interest in alternative establishment systems had grown due to potential labour, work rate, cost saving, crop performance and soil structure benefits.

“As with all new technologies, we needed to validate some of these claims under a long-term trial system to capture the cumulative effects. More recently we have incorporated environmental metrics, such as soil carbon and greenhouse gas emissions into our work,” Forristal explained.

To provide clarity and scientific backing to some of these claims, various experiments have been conducted at Knockbeg since 2001. The effect of establishment system (plough versus min-till and straw incorporation) was quantified over a seven year trial, where continuous winter wheat was the main crop. Further research studies from Knockbeg evaluated various nitrogen application strategies for conventional or min-till systems, and a nine-year study assessed the impact of cultivations and rotations.

Dermot Forristal, pictured above, delved into more than 20 years of research from Knockbeg at the Teagasc National Tillage Conference.

Providing a summary of the results from these experiments, Dermot Forristal explained that performance of continuous winter wheat was often similar between conventional and min-till establishment systems, with the exception of wet years where performance from the min-till system dipped. This is illustrated in Figure 1 below.

Figure 1: Yields of winter wheat at Knockbeg from 2001 to 2022 under plough and min-till systems

Over the duration of the study, non-plough systems yielded lower costs and higher work rates. However, this was highly dependent on the depth of the min-till operation. Basing costs at 2024 levels, Dermot Forristal explained that the cost of establishing using min-till was 67% of plough-based systems, whereas direct drilling costs were 30% of plough-based systems.

Although a more comprehensive soil carbon analysis is required, the Knockbeg research showed that cultivation system had relatively little impact on soil carbon levels. However, min-till systems did increase earthworm and slug populations.

Concluding his presentation to the Teagasc National Tillage Conference, Dermot Forristal explained: “Non-inversion systems generally are high-output, lower cost and do provide some soil benefits. However, in an Irish context, the benefits can sometimes be overestimated. In our climate, the benefits to soil carbon and greenhouse gases are small, whereas straw incorporation and cover cropping may contribute more.”

As non-inversion tillage systems can be challenged by wet autumns and later springs, Dermot Forristal advised farmers to “take a flexible approach” if opting to implement such systems on their farms. He also reminded farmers of the grass weed threat associated with min-till systems, noting that stale seedbeds, ploughing and rotations could play an important role in their control going forward, as earlier sowing and milder climates, along with herbicide product losses and resistance issues, could see farmers altering their strategies to control grass weeds. Indeed, he explained, future challenges will need long term research sites, incorporating rotation and crop establishment, to facilitate sustainability research incorporating all aspects of crop agronomy and soil protection.  

For more information, Dermot Forristal’s full presentation and paper is available to view here.