Getting To Grips With Companion Planting

Growing different plants next to each other, in the same field or plot, is alien to many farmers but less so for ‘growers’. Farmers who talk to their neighbours with gardens may well find they have been growing combinations of crops for decades. The world of horticulture knows that marigolds create natural pesticides that keep nematodes and beetles off tomatoes, asparagus and squashes. That growing beans, which fix N, helps maize, brassicas and beet along. Horticulture has tended to be wary of chemical controls, both from the cost and a natural leaning towards organic methods.

Farmers on the other hand have mainly taken the route of a single crop which can be managed through pesticides and fertilisers. With professional agronomic advice the system has been universally adopted and experience and knowledge has been developed which enable there to be calculable costs and predictable effects. Farmers are moving from conventional chemical methods to those based on biology. Effectiveness; cost; product resistance; soil condition; chemical runoff; negative environmental issues are just some of the drivers.

Companion cropping has become one of the ‘go-to’ farming systems favoured by advisors and others as being good for the environment and soils. Yet little has been recently published on the topic – by far the most comprehensive comes from Kentish farmer Andrew Howard whose Nuffield Farming Scholarships Trust Report of July 2016 ‘The potential for companion intercropping on UK arable farms’ takes a global look at it. It provides a substantial introduction to intercropping and guidance for UK arable farmers to help encourage onfarm experimentation. With a rise in the prevalence of weed, insect and disease resistance brought on by monocultures and high-input farming, intercropping can help farmers grow crops with lower inputs. The report makes the case for its potential to regenerate degraded soils and increase productivity for arable systems increasingly reliant on external inputs.

In his report Andrew explains that the impetus to apply for a Nuffield Scholarship came from his friend Tom Sewell who in 2013 was in the middle of doing one. Andrew found the idea of travelling the world and meeting the best farmers on the planet ‘strangely appealing’. The previous year he had been to a meeting where a French farmer, Frederic Thomas, was speaking. He talked about No-till and cover crops and then at the end of his talk he spoke about companion cropping with oilseed rape. This seemed like a crazy idea but got Andrew to experiment on the family farm. It worked so well he became hooked, and realised he had a useful topic for his Nuffield Farming Scholarship.

The study took in five separate trips: the first, May 2015, to France, chosen for their similar climate plus the fact they “ahead of us in terms on companion cropping and intercropping research and on-farm practices.” The second, JuneJuly 2015, was four weeks in the USA and Canada. The third, November 2015, was to Germany, Switzerland and France, and the fourth was 7 days in Kenya and another 10 in South Africa. Finally in June he had three days in Sweden and two in Denmark, with a particular interest in seeing how it works with their strict environmental laws, which Andrew sees as being applied in the UK before too long.

‘Companion Cropping’ has a wide meaning and Andrew needed to work to a closer definition which he describes as:

“The growing of two or more crop species where part or all of their crop cycle overlaps temporally and/or spatially, where one or more of the component species is taken to harvest”

He then found that rather than being new, the technique was a regular part of farming until mono-cropping became the norm.

• In 1923 57% of Ohio’s soya bean acreage was intercropped with maize

• In 1972 98% of cowpeas in Africa were intercropped with maize

• In 1975 90% of beans in Columbia were intercropped.

And the history goes back 5000 years to native Americans who grew maize, beans and squash together, the beans fixing N for the maize and using it as a trellis, and the squash grew low and shaded out the weeds. When different species like each other they over-yield – produce more than they would in monoculture. The figures are considerable: conventional farmers in Canada will experience over-yielding in intercropping in 75% of instances, while over-yielding occurred 47% of the time in organic crops. Inter-cropping performance is measured, often using the following formula:

LER = (Mixed yield 1 / pure yield 1) + (mixed yield 2 / pure yield 2)

where LER is the Land Equivalent Ratio, or the amount of land it would need to grow the two crops separately. When LER is greater than 1, then there’s a yield advantage, but not of course necessarily more profitable. So the calculation is made for the Relative Total Value, the Monetary Equivalence Value or the Income Equivalence Value.

He found farmers experienced both benefits and drawbacks of mixing plant species. The benefits are the way combining species increases the resistance of thee crop as a whole to pests and pathogens Ian Wilkinson was persuaded to use companion cropping after meeting Nim Barnes who ran a charity called Foresight. “You are an agriculturalist,” she said, “have you thought about the minerals in your diet?” We hadn’t. “You analyse plant tissues,” said Nim, “so analyse yourselves!” We did, and we found that we were deficient in many minerals.

Ian found that over 50 year period there has been a falling levels of minerals in milk, meat and vegetables as production has become increasing intensive, and at the same time herbs and deep rooting legumes have been ignored. He bought into the idea of raising mineral availability by using these unfashionable plants to mine minerals through livestock and cover cropping. Ian’s expertise of crops comes through his position as MD of Cotswold Seeds. In 2013 he bought a 107 acre Cotswold farm, mostly made up of brash and which produced an annual crop of spring malting barley. The farm now has deep rooting leys as a break, using nurse crops and inter crops, undersowing clover to wheat, and rye and vetches as winter green manure. Instead of the land being bare for much of the year, the aim now is to keep it covered, and with mixed species.

Sheep are brought in to do some mob grazing which is providing a youngster the opportunity to build a flock, and at the same time make major improvements to soil quality. Ian says the ultimate companion crop is a diverse herbal ley which works well when mob grazed, which makes it more palatable, so intakes are higher. With better protein there’s greater lightweight gain and more milk. Sanfoin is the winner in Ian’s eyes. The diverse deep rooting ley is its drought resistance. Ryegrass, with its shallow roots, stops growing in a drought while thee deep rooting ley keeps going. Companion crapping is as vital as cropping, and Ian has fund the sheep have done wonders on his Cotswold farm. The trick is to integrate livestock with the arable acreage.

Tips from horticulturalists

Sue Sanderson from Thompson-Morgan says that companion planting is all about creating communities which have mutual benefits for each other. The benefits can be pest control, or improved pollination of fruit and vegetables. Intercropping, where fast growing crops like lettuce or radish are sown between wide rows of Sprouts or parsnips makes good use of space and suppresses weeds. Tall plants like peas and sweet corn create shaded conditions which prevent crops like lettuce, coriander and spinach from bolting. Most herbs have scented leaves that help repel insects. Others attract insects and birds and these can be useful in drawing in natural predators which feed on slugs, hover flies and other pests which they like eating. Not all species are good companions, however, and the advice is never grow these plants side by side: Alliums (onions, shallots, leeks, garlic) with legumes (peas, beans, peanuts). Tomorrow’s agronomist will need knowledge not only of chemical products but also of companion cropping. And so the wheel turns full circle!

Mike Donovan