A long-term research project has compared ploughing with min-till methods. Louise Impey looks at the findings

The latest results from a large-scale rotational study being conducted in Suffolk have confirmed the importance of rotation and cultivation choices on yields and gross margins, with a managed approach giving the highest returns.

The findings also highlight the developing threat posed by grass weeds, especially where minimum tillage prevails or the rotation is down to continuous wheat.

The STAR project, which is funded by the Felix Thornley Cobbold Trust, has been studying the impact of a range of establishment techniques within different arable rotations since 2006.

Four rotations and four cultivation systems are being compared (see table), with the findings being used to produce cumulative gross margins.

Not surprisingly, recent farmer interest has been focused on the use of both spring break crops and alternate fallow, given the rising problems and costs associated with grass weed control.

While wheat yields have been at their highest with the plough, deep tillage is not far behind, says Ron Stobart of NIAB TAG, who manages the project.

“Yields using deep non-inversion tillage were only 2% lower,” he points out. “With shallow non-inversion tillage, there’s been a 6% drop.”

But gross margins have been highest with the managed approach, reflecting the need for cultivations to be able to cope with variable weather and soil conditions and the importance of making good decisions, notes Mr Stobart.

“Ploughing was next in the financial order, but the figures don’t take speed of working into account. On some of the larger farms, being able to plough every year just isn’t an option.”

Grass weeds are showing themselves in the continuous wheat and shallow tillage plots, he reports. “We expected black-grass to be the main challenge, but brome is proving to be the worst culprit. We’ve had to spend an additional £70/ha in the shallow inversion plots this year, just to get on top of it.”

Grass weed levels were low at the outset, he points out. “It shows how quickly problems can develop, despite targeted herbicide programmes.”

Ploughed continuous wheat plots, together with all other rotational approaches, continue to have low numbers of grass weeds.

Mycotoxin levels have also been monitored in the project. In 2007, there was one plot within the continuous wheat rotation that had DON levels above the EU limit, use of the plough then reduced that considerably.

“One unexpected finding was that the deep tillage plots had slightly higher levels than the shallow tillage,” reveals Mr Stobart. “That may have been due to the fact that we used a Sumo in the shallow tillage plots, as it has both feet and discs, giving two points of working and resulting in very effective surface mixing.”