Ambitious project looks at benefit of cover crops

Three-year programme looks at impact on field rotations

British researchers have launched an ambitious trial programme to quantify the cost-benefit of including cover crops in field rotations.

Led by ADAS and funded by AHDB, the work aims to lay bare the longerterm effects of cover crops and assess the impact of cultivation, establishment and destruction techniques.

The project, over the next three years, will use field trials and experiments on contrasting soil types to build on AHDB’s knowledge of cover-crop usage.

While the trials – on AHDB monitor farms in York, Huntingdon and at Sittingbourne – will be of interest across the UK, AHDB Cereals & Oilseeds knowledge exchange manager Gavin Dick said cover-crop success comes far harder for Scotland’s farmers as they have a far shorter growing period.

“My fear is that farmers are simply following a fashion, rather than growing cover crops as a management strategy to resolve a problem.

“Cover crops aren’t cheap to grow so they should really only be considered as a method to fix an issue such as nutrient leaching or soil compaction,” he said.

At Cuplahills, Balmullo, arable farmer and agricultural business consultant Stephen Melville has been trialling cover crops for the last four years.

“As we have no livestock I began looking into cover crops as a method for improving soil by creating a source of organic matter,” he said.

“Where previously unused nitrogen was leaching down through the soil profile, cover crops provide a way to draw it back out.”

As a trials host for Kings and Frontier, Stephen’s initial focus examined the potential for oil radish – a fast growing brassica crop that has been proven as excellent at catching residual nitrogen.

“In Scotland’s short growing season we need green plants that will germinate quickly and grow vigorously.

“Often the best crops want warm soils but, unlike growers south of the border, we’re planting in the first week of September at the stage soils are really starting to cool down,” he said.

While the first year yielded fantastic results at Cuplahills, during a later trial not all of the oil radish seeds germinated.

That trial site was then put for oilseed rape, and oil radish consequently began to pop up throughout the crop.

“We ended up with a contaminated oilseed rape crop and, as both plants are members of the brassica family, there wasn’t anything we could do about it,” Stephen added.

But that trial has not put Stephen off the use of cover crops and he has grown successful mixes of forage rye, vetch, tillage radish, phacelia and berseem clover.

He said it is difficult to quantify the value of cover crops as many factors cannot be assessed over such a short period of time. However, the soil at Cuplahills is showing marked signals of improvement, particularly in terms of an improved breakdown during ploughing.

Stephen believes water quality has also improved, erosion has been reduced, and crops have provided beneficial cover for wildlife habitat.

Picture: Kim Cessford. Stephen Melville has been trialling cover crops for the last four years at Cuplahills.