Photo: Fogelina Cuperus
Large-scale agriculture is the main cause of biodiversity decline in rural areas. But if farmers adopt a different approach, they could reverse this decline, according to research by scientists at Wageningen. They discovered that strip cropping can help restore biodiversity. What is more, it makes the food production system more robust.
According to project manager Dirk van Apeldoorn, perhaps one of the best side effects of strip cropping – more on that later – is that the farmers who implement it start to enjoy their work more. That is quite something. Van Apeldoorn is an agronomist who seeks to boost biodiversity in agriculture; in other words, he acts in the interests of plants, animals and the soil. But it is people – the farmers who cause biodiversity loss through their (often imposed) large-scale approach – who can resolve that problem, says Van Apeldoorn.
That is more likely to happen if they are motivated and derive pleasure from their work.
But what is strip cropping exactly and what makes it a nature-based solution? Van Apeldoorn: “In strip cropping, arable farmers sow multiple crops alongside one another in a single field. In doing so, the farmer increases the diversity on the land. That leads to a more robust system than larger plots, which are susceptible to diseases and pests.”
‘Strip cropping leads to a more robust system than larger plots, which are susceptible to diseases and pests’
Photo: Dirk van Apeldoorn
In a nature-based solution, you move in tandem with nature instead of trying to thwart it, explains the WUR scientist. “For example, you let natural pest surpressors such as hoverflies eat your aphids rather than using chemicals. But that does mean you need to make sure the hoverflies can do their job. On farms that are large-scale monocultures, the hoverflies can’t reach the middle of the field because they can only fly 150 metres. After flying that distance, they need nectar and sheltered spots. That is why we include strips with flowering arable plants in the strip cultivation, rather than just along the verges.”
A varied ecosystem is naturally stable, explains Van Apeldoorn. There is variation along the dimensions of time and space, and there are a variety of different habitats. Strip cultivation replicates that situation, with diversity in the crops over time (crop rotation) and space (multiple strips in a single field). That makes it more difficult for diseases and pests to spread: they get stopped by the next strip along, which contains a different crop.
The variety of habitats in the field thanks to the different crops also creates stability, with more room for insects and birds to forage and find shelter. Van Apeldoorn: “We are also experimenting with agroforestry, where we combine nut trees with annual crops such as carrots. You plant trees and hedges to create a strip of land that is not tilled, which can become a source of biodiversity. What is more, you can prevent damage to crops from the wind.”
Returning to the subject of the farmers’ pleasure in their work, Van Apeldoorn says, “In large-scale agriculture, the farmer sits up high on their tractor and has little contact with the soil or the plants. Farmers who practice strip cropping visit their fields more often because the different crops have different harvest times. That increases their involvement in their land, so they become more interested and get more pleasure from their jobs.”
‘When farmers practice strip cropping, people come to watch. This reawakens interest in food’
One key result from the research is that yields from relatively wide strips are at least on a par with the yields from large-scale cultivation. Farmers can also try out combinations of crops that boost or protect one another. Furthermore, strip cropping always spreads the risk: if one crop does not do well, there will always be a couple of others that do perform well.
As an example of a beneficial crop combination, Van Apeldoorn cites winter cereals and cabbage. “Aphids are attracted by the winter cereals but they will not cause much damage. However, many of their natural enemies are attracted too. Their presence then keeps the cabbages free of aphids later in the spring.”
Potatoes and a grass-clover mix also make a good combination, with yields that are up to 20 per cent higher in trials. “We don’t yet fully understand what the reason is for this. Perhaps something is going on in the soil or maybe there is a particular microclimate, but we need to investigate it further.”
On the subject of soil, it too can improve with strip cultivation. Not only are larger areas left untouched (for example, the flowering verges and hedgerows), but smart use of neighbouring strips as routes for the heavy farm machinery can prevent the compaction of soil in the other strips. And once nature is allowed to do its job, fewer pesticides are required.
What about biodiversity? Does it really increase in fields with strip cropping? “Absolutely,” says Van Apeldoorn. “After switching to this method, we see a gradual increase over the years in the numbers of insects, spiders and birds. But it depends in part on the surroundings. After all, the creatures need to be able to reach the strips and if the strip cultivation field is surrounded by green deserts, there is no animal life all the way to the field so it fails to attract anything. There has been a dramatic decline in field bird populations anyway. The only field bird that has managed to adapt to the monoculture to some degree is the yellow wagtail. Despite that, the wagtails still seem to prefer strip cropping to the same crops as monocultures.”
Monocultures are a big threat to biodiversity in agriculture. The solution, according to WUR researcher Dirk van Apeldoorn, is to reduce the areas – for example by strip cropping – and to combine different species.
As regards insects, Van Apeldoorn finds a clear rise in diversity. The same applies for wild plants. “We have been studying this for four years now and we are still seeing development. But there are big fluctuations. We saw ten times as many ground beetles some years compared to others. More research is needed to understand how everything interacts and what more we can do. But the fact that we see an increase in diversity is already very good news. It shows nature can recover if only we give it the chance to do so.”
Van Apeldoorn feels the time is ripe for a transition in farming. “Everyone can see we are at the limits. The soil is becoming exhausted and diseases and pests are becoming resistant to crop protection agents. Farmers have long pinned their hopes on technological innovations, but that will take too long. By switching to strip cropping, they can already take action. It doesn’t require a major change in their farming practices either because the strips are wide enough to allow standard farm machinery to drive along them. Farmers themselves want to make the change and call us for advice, to such an extent that we can hardly cope with the demand.”
It is not only farmers who are enthusiastic, the general public is too. Van Apeldoorn: “Strip cropping looks attractive with its patterned variation. I know a farmer in Wageningen who says he can hardly get on with his work because every ten minutes someone comes up to the hedge and asks where they can buy his vegetables. Nobody ever asked where they could buy his sugar beet when he had a large-scale farm in the polder in Flevoland.”
Van Apeldoorn cites another example of a farm just outside Almere. When the farmer practised large-scale cultivation, local residents were always complaining about the dust and noise. “Now she practices strip cropping, they come to have a look, with parents showing their children the farm. That generates interest again in where food comes from. Agriculture is currently a source of problems, but it should become a source of enjoyment. We need to make a choice as a society. If we think the only purpose of agriculture is to produce food, that will lead to yet further increases in scale and efficiency. But if we say farmland should also deliver biodiversity and cultural landscapes, then strip cropping is a good option. It would be ideal if we were also to pay farmers for such ecosystem services.”