How to get more from cover and companion crops

• Crops including legumes more popular

• Proper nutrition will maximise potential

• Polysulphate ideal source of nutrients

Good nutrition is helping growers maximise the benefits of legumes in arable rotations and forage-based systems.

Many people focus on ways crops like clover can generate their own nitrogen – both for yield and for the subsequent cropping. But legumes also need other nutrients to maximise their potential, says ICL Growing Solutions agronomist Scott Garnett.

“It is too easy to think that because cover and companion crops contain a high proportion of nitrogen-fixing legumes, that they are self-sufficient from a nutrition perspective.That is simply not the case.”

Legumes need nurturing like any other crop, says Mr Garnett. To maximise their potential – and their ability to fix nitrogen – they require proper nutrition. This includes adequate supplies of nutrients like phosphate, potash, magnesium and sulphur.

“Without adequate sulphur, the plant is simply unable to fix sufficient Nitrogen to maximise yield, produce proteins where necessary and its ability to contribute to subsequent crops will be significantly reduced.”

New thinking

The area of cover and companion crops is growing rapidly – encouraged by the Sustainable Farming Incentive and efforts to reduce nitrogen use. But their management is a relatively new area for industry advisors.

SFI option NUM2 pays £102/ha for improving grassland by growing legumes from spring until early autumn. Meanwhile, growers can receive £151/ha under SFI options LIG1 and LIG2 to include flowering grasses and wildflowers in grass leys during the summer months.

“There are further benefits to be had from using companion crops in arable rotations,” says Mr Garnett.

One of the biggest questions is the amount of nitrogen they can they deliver the extent to which they can reduce our dependency on bagged fertiliser, he adds.

In a livestock situation, adding nutrition to increase clover is easier to justify where better management translates directly into greater milk or meat production. The same can be said when growing commercial crops of peas and beans where good yields are important.

Pea and bean trials with the Pea Growers Research Organisation (PGRO) suggest Polysulphate (48% SO₃, 14% K₂O, 17% CaO and 6% MgO) provides a nutritional boost that results in a 10-15% yield boost.

“We already know adding a product like Polysulphate to legumes directly translates into yield and quality benefits,” says Mr Garnett.

Sulphur supply

Key nutrients required by crops in both livestock systems and companion crops in arable rotations are zinc, manganese, cobalt and molybdenum – as well as phosphate, potassium and sulphate.

“Sulphur is particularly important, not just to drive the highest levels of nitrogen utilisation, but also to improve protein content which is important in both forage and cereal crops.”

Polysulphate, either in fertiliser blends or by itself, has proven particularly beneficial in both organic and conventional farming systems.

It  delivers high levels of usable sulphate, with its prolonged release reducing many of the potential environmental issues associated with other sulphur sources.

Mr Garnett says multi-nutrient fertilisers based on Polysulphate are perfect for providing macro nutrition and are also able to be a carrier for micro nutrients.

Given the central importance of legumes to future UK strategy, ICL believes it is now time to look at how growers can maximise the benefit of these products.

Growers could also benefit by re-investing some of SFI income into improving the nutrition and management of cover and companion crops, says Mr Garnett.

“With many sources suggesting a well-managed cover crop can fix 80 – 100kg N/ha and companies exploring the possibilities of increasing their genetic potential further, it is certainly an interesting topic that merits further debate,” he adds.