A trial carried out at Severn Trent’s biogas farm in Nottingham in the UK has confirmed that it is feasible to undersow forage maize crops with grass.

Maize crops grown in this way will generate fresh weight yields of 50t/ha. This does not include any contribution from the under sown grass.

The harvested fields can be grazed by sheep and cattle in subsequent years.

Other benefits of this approach to the management of maize crops include enhanced soil and water quality.

Severn Trent farm manager, John Jackson, said: “Undersowing a fast-rooting ryegrass mix has helped us create a stronger soil structure on our maize fields, minimising soil damage at harvest and improving nutrient management for the next crop.

“This is especially so on lighter soils.

“We’ve seen reduced erosion in the trial plots, which also helps prevent run-off and nitrate leaching, therefore protecting local watercourses – with no penalty for maize yields.”

Jackson and his team commit to harvesting maize in September, when soils are more robust. Therefore, drilling crops in April is advised.

“Whether you’re growing maize for grain, forage or biogas, as long as the soil temperature is reaching 8-10°C for four to five consecutive days and seedbed conditions are good, you can get drilling,” Jackson explained.

“We drilled our maize in mid-April, with the ryegrass under-sown seven weeks later in mid-July, when maize was at the 4- 5 leaf stage and well-established.”

Drilling maize

Jackson encourages the bespoke drilling of the grass seed, rather than broadcasting it. It is an approach that helps to minimise crop competition.

He stressed:

“Ground contact is key. So the undersowing was done at the same drilling width as the maize. Going any wider, it results in drift. Growers need to ensure maize remains the main crop.”

For farmers in a priority Severn Trent catchment area, match-funding is available through STEPS (Severn Trent Environmental Protection Scheme).

There are numerous options from under-sowing to cover crops. Growers will also have access to a local agricultural advisor for support.

Under sowing may not be an option if maize is planted out under plastic.

The one exception, in this context, relates to the use of fully compostable films, which fully degrade within six weeks of planting.

Severn Trent has also confirmed the benefits of sewage sludge as a fertiliser source for maize crops.