Growers are being urged to consider under-sowing maize with grass – and reap the benefits of better soil health.
Retention of important nutrients, reduced topsoil loss and improved harvestability are just some of the benefits – but timing and species selection are crucial, says David Linton, commercial manager for grass seed breeder Barenbrug.
“We all recognise that maize is a high-risk crop for soil health – and a cover crop like grass is probably the single best move a grower can make to reduce that risk. Yet it remains something of a niche undertaking.”.
Right species
Water quality is potentially the biggest win, says Mr Linton. Grass will help retain recognised ‘problem’ nutrients such as phosphorus and nitrates, which water companies regard as potential pollutants along with excess sediment.
“Retaining those nutrients in the soil makes them available for the following crop. Trials have shown how under-sowing maize provides a greater reduction in nitrate leaching than autumn-established cover crops after maize.”
Some growers remain reluctant to under-sow maize crops with grass because of the perceived impact on yield or quality. But Mr Linton sasys trials have proved that under-sowing has no significant effect on yield, metabolisable energy or starch content.
He attributes this concern to inappropriate species selection for under-sowing. “There’s been a tendency to recommend Italian ryegrass, but that can be absolutely the wrong choice, particularly if sown too early,” he warns.
“It’s one of the fastest-growing grasses; that’s why farmers like it. But those same attributes – rapid germination and swift establishment – present a competition problem for maize, particularly during the first six weeks post-emergence.
“There’s also the consideration, especially where arable farms have added maize to the rotation – for example for AD – that IRG is a weed species. You want to avoid purposely introducing what may become a weed burden.”
Mr Linton has a two-fold suggestion: let the maize establish first without grass and avoid the ‘Italian mistake’ by sowing alternative varieties when the maize has reached 6-8 leaves.
Branched rooting
“There’s further benefit from a species like tall fescue because of its deeper, branched rooting system. This provides a much bigger boost to soil structure and health post-harvest, as well as being able to soak up nutrients from a greater volume of soil.”
What’s more, fescue’s branched rooting also improves the soil’s bearing capacity – essentially allowing the soil to take a greater load without damage, a worthy consideration if conditions turn wet before or during harvest.
Barenbrug has developed a ‘maize-friendly’ green cover option, utilising tall fescue genetics. It has been selected for a combination of traits – including those that favour fast germination. This gets the seedling out of the soil quickly,” says Mr Linton.
It also slows growth post-germination to avoid competing with the maize. “Our recommendation for Proterra Maize is to wait until the maize has reached the 6-8 leaf stage, then sow at 12kg/ha with an inter-row drill.
Mr Linton says: “Proterra Maize is a better option than Italian ryegrass, especially in an arable rotation. “This is a cover crop that won’t rob the maize of sunlight, moisture or nutrients,” he adds.