“We need to apply ancient farming principles on a modern scale”
By: Anne Roos van Wijngaarden
From March 2, 'Onder het Maaiveld' can be seen in Dutch cinemas. The documentary is a snapshot of the soil situation in the Netherlands and addresses the question: what does sustainable soil management look like? IUCN ecologist Caspar Verwer is the initiator of the broader programme: “We must aim for an increase in organic matter in the soil. Then we feed the soil life, we increase carbon sequestration, and the soil starts to act like a sponge.”
'Healthy soil' should ring all kinds of bells, from the nitrogen crisis to the stricter fertilizer rules that came into effect on 1 March for arable farmers and dairy farmers. Due to conflicting interests from politicians, municipalities, farmers and interest groups, the subject of 'sustainable soil management' remains controversial, but healthy soil will require a major shift towards a balanced relationship with nature.
This is a major challenge, as Caspar Verwer knows from his career as an ecologist at the International Union for Conservation of Nature (IUCN). Fortunately, in recent years he has seen one promising sustainable soil project after another. The seed for a healthier Dutch soil has therefore been planted.
What characterizes a healthy soil?
“To measure that, we mainly look at the 'ecosystem services' that the soil can provide. At IUCN we use a list of services drawn up by the Food and Agriculture Organization (FAO). This concerns, for example, climate regulation, water purification, carbon sequestration, soil fertility and the quality of food production.”
Benthic life in the Netherlands is declining. How did that happen?
“Intensive agriculture in particular has a major impact on the soil. This includes heavy machinery that drives across the land, the use of chemical pesticides and the manure surplus that is injected into the land by farmers.
There is also still too much plowing, which keeps mixing up the soil life that has been able to build up. Plowing has long been a positive thing for agricultural yields, because new crops grow well in loose soil, but you now see – especially with more extreme weather conditions – that the soil no longer has the resilience it naturally has.
There must be more organic matter in the soil, so that more CO2 can be captured and the soil retains water for longer. Some farmers do that very well, but other farmers just continue as before.”
Which innovations are promising to prevent soil escalation?
“Most alternatives are not actually innovations, but very old agricultural principles. Take crop rotation, for example, where you ensure that a different crop grows on your plot every year. Another old principle is to keep the soil covered, for example with green manures that add certain nutrients to the soil. You can dig it under and plant it again.”
So disruptive innovations are not an issue?
“Well, you want to apply those old sustainable agricultural principles on a modern scale. That translation is the major challenge and calls for innovation.
I am reminded of North Holland bulb farmer John Huijberts. He has developed a machine that can lift a layer of green manure and plant the bulbs underneath. Then he throws down that layer again, which then dies and can then lie on the land to cover the soil, so that the weeds are immediately suppressed. The bulbs just grow through it. By leaving large parts of his land alone, the soil can recover and insects can increase in numbers.
We call such a farmer who is very innovative a lighthouse farmer. The problem with these frontrunners is that they often do not receive support from the government and that existing rules sometimes have an obstructive effect. They learn by trial and error and have to get to work themselves.”
What other industries affect the soil?
“Take, for example, the management of public space in the Netherlands. You can adjust the management of parks, public gardens, green strips and verges in such a way that the soil is disturbed less. An example is regular flail management. Clippings remain on the ground, resulting in an accumulation of nitrogen. As a result, the vegetation becomes overgrown and the species richness decreases. Instead, you can also remove the clippings, then the verge becomes atrophied and the diversity of species gradually returns.
The construction sector could also do more. An example is the Park Amstelwijck district of Dordrecht, which was recently built. The project developer ABB first looked at the existing vegetation and then included it in the design. This means, for example, that pipes had to be laid around trees. They also chose to only fill with sand where it had to be built, so that the houses are a bit higher than the garden. Those level differences are very complicated for managers, but great for the soil.”
What about the soil in the city? Is there still an environmental benefit to be gained?
"Absolute. Due to climate change you see that heat stress arises in urban environments and that is a major problem. You can partly tackle this by aiming for healthier soils with vegetation, because that cools the air (through water evaporation). Cities also suffer from flooding. The soil can function as a sponge that absorbs that water, provided you ensure good rooting and enough organic material.
Municipalities are working on this. For example, the Municipality of Arnhem is going to 'de-stone', so remove the pavement. Parking areas do not have to be completely paved, semi-paving or permeable paving can also be used. You can simply drive over it and at the same time rainwater can replenish the water table.”
Can healthy soil solve our nitrogen problem?
“It's actually the other way around. We have been emitting too many nitrogen compounds for decades. This nitrogen deposition has led to acidification, particularly in the higher sandy soils, as a result of which important building materials such as potassium and calcium have been displaced from the soil. The chemical balance is disturbed. You have to tackle this excess of nitrogen if you want to create the conditions to make the soil healthy again.
There is a lot of experimentation to speed up the recovery of degraded soils, for example with rock flour. Within the program Onder het Maaiveld we are looking at a different method, soil grafting. We have set up a test set-up in Wageningen with cylinders with sand-peat-clay soils. We then graft a piece of healthy soil onto those soils to see if you can promote the recovery of the soil life. The results of several soil transplant trials are positive.”
This is the only option. Trees for future organization has such a demonstration farm in Kenya which is really successful.