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How to bring life to dying soils

Together, these techniques have transformed their land. “The soil should crumble like a brownie would,” Overby explains. When he took over the farm from his parents, the soil had a lot of fine particles. The silt, sand, and clay making up the soil would come apart easily. After a heavy rain, the soil would become very sticky, as the fine texture didn’t allow much room for drainage.

Today, the soil is dark and full of large clumps, with bigger gaps between the particles. Water is now able to reach the deeper layers of the ground. “When you walk across my fields, it feels like you’re walking on a carpet,” Overby says.

For farmers like him it isn’t an option to ignore what lies beneath. Soil is critical for the food everyone eats. Healthy soils matter not just for producing 95% of global food supplies, but also for safeguarding other aspects of human health. Soils sequester a massive amount of carbon (over twice as much as the atmosphere and all plants combined). In addition, microbes in healthy soils lead to the development of antibiotics and other medicines. 

So it’s alarming that this foundation of food production and health is in trouble.
 
Up to 40% of the world’s agricultural land is already degraded, but fairly simple techniques can reverse the damage
 

Up to 40% of the world’s agricultural land is degraded, and it’s estimated that the economic losses amount to $40 billion (£30bn) per year. But almost all of the world’s arable land is already being farmed, so it’s not an option to leave existing plots and move on to new ones.

Intensive farming, climate change, deforestation, industrial activity and natural processes have all taken their toll on soil. The effects can be physical (such as erosion of fertile topsoil), chemical (such as acidification of soil), or biological (such as loss of microbes). Where soil remains, overworking it makes it weaker due to less nutrient absorption and drainage of water – for instance, when soil becomes compacted by overgrazing of livestock.

But fairly simple techniques can make a big difference. In Ghana, planting elephant grass helps to hold soil together. In Burkina Faso, the zai (half moon) method involves farmers digging large holes in soil and putting in compost when rains are arriving in order to conserve water and soil. In India, using trenches and small walls during the rainy season helps to preserve nutrient-rich topsoil and prevent soil erosion.

READ MORE- Soil: it’s what keeps us clothed and fed

Indeed, around the world farmers and scientists are working to invigorate soil where possible. And they’re finding that sometimes the best solutions are the basic ones.
 
In many ways, the best way to reverse nutrient depletion in the earth is simply to leave nature to it. This is the basic principle behind practises like regenerative agriculture, conservation agriculture and no-till agriculture. 

These approaches share a commitment to reversing human-induced stress to soil. For instance, growing perennial crops reduces the need to till and disturb soil, preserving its integrity and increasing its resilience to drought. In essence, regenerative agriculture aims to minimise soil disturbance, combined with other techniques for improving the health and productivity of soil. 

The transition isn’t always completely smooth. Overby reports that soon after going no-till, the farm saved time, fuel, and wear and tear on tillage equipment. But they did initially need more herbicide to deal with the weeds that would previously have been removed by tillage.

And while the overall philosophy may be of embracing natural processes, some human management is needed, especially for subsistence agriculture. Eugene Rurangwa, a land and water officer for the Food and Agriculture Organization of the United Nations (FAO), is based in Dakar, Senegal. He says that in the West African region where he works, “we are dealing with an increasing population, sometimes a very poor population, that really needs to use land. More than 80% of our population are using agriculture as the main means of living. To tell them just to leave the soil, which actually could be an ideal situation, is very difficult. So we hope for a sustainable soil management practice, to be able to manage the healthy condition of the soil.” 

Plus, in some cases minimal management may be healthier than the absence of management. Rurangwa explains that minimum tillage, or disturbance of the soil, allows for aeration of the soil, thus enabling the circulation of water, air and nutrients to plants.

Low-till farming is often combined with the use of cover crops, which help to suppress the weeds in place of vigorous tilling. There are other benefits as well: keeping soil covered with organic matter nourishes it, improves the absorption of water, and shelters it from wind erosion.
 
 
A subset of regenerative agriculture is farmer-managed natural regeneration (FMNR), where farmers plant woody vegetation or trees alongside crops. This practice, most common in West Africa, has led to increases of up to 25-46% in soil organic carbon (a key measure of soil health), as well as lowering wind speed and creating more shade and greater soil moisture. This is crucial because the 15 West African countries under Rurangwa’s aegis all face water scarcity. “Water is the first important input, the first element for soil to live,” he says. 

As with all regenerative practices, farmers need to see the benefits of FMNR to remain committed to it. Research in Niger has suggested that households observing FMNR have had their revenue increased by around 10%. These households can sell the wood and other biomass produced from FMNR while improving soil health in the longer term.

With agroforestry, or the integration of trees into farmed areas, it can take several years to see the full benefits, for instance increased crop yields. But Rurangwa says that some benefits appear even from the first season, such as less erosion.

Yet these benefits won’t appear at all if farmers don’t have secure rights to the land they farm. “It’s really very difficult to apply any techniques or, or to put any kind of long-term infrastructure on land that doesn’t belong to you,” Rurangwa points out. “So land tenure security is really, really key in advancing and sustaining those techniques.” Paying attention to land governance can also help to resolve conflicts that might lead to land damage. For example, conferring with traditional authorities could build collaboration between pastoralists and farmers for integrated crop and livestock management.
 
 
Part of doing less is applying fewer agrochemicals to the soil, which if used without expertise can be damaging. “If you apply fertilisers without knowing the status of your soil, it is really inappropriate and very dangerous” for the plant, the soil and the environment, according to Rurangwa, who sees some farmers he works with misapplying chemicals. Soil pollution, whose causes include agrochemical use, degrades land, reduces crop yields and sickens humans and animals.

Rurangwa advocates for using organic fertiliser, and less of it, for instance through more precise microdoses of fertiliser using fertigation (application of fertiliser through irrigation water).

Fertiliser briquettes – which can release nutrients more slowly across a much smaller surface area – also have led to higher maize yields and increased nitrogen uptake compared to conventional granular fertiliser in Ghana.

Bio-organic fertiliser may be especially beneficial. As it contains living microorganisms, such fertiliser can improve microbial balance and ultimately crop quality. These microbial communities do a lot of invisible work in the soil, such as converting atmospheric nitrogen into a form that plants can use. Rosa Cuevas, a soil scientist at FAO’s Global Soil Partnership, calls biofertiliser “an inexpensive and safe alternative to chemical fertilisers”. For instance, “in the case of nitrogen, biofertilisers have the potential to reduce nitrous oxide emissions (a greenhouse gas around 300 times more powerful than CO2), and contamination of groundwater and coastal ecosystems”.

Coating seeds with special microbial cocktails can also help the plants stay robust. FAO provides some farmers with enhanced seeds and fertilisers. But Rurangwa warns, “It doesn’t replace the improvement of soil health. Even if you have improved seeds, you can’t put improved seeds in poor soil and think you’ll get good results.”

Overall, with less disturbance of the soil, Overby says, “The microbes all have a chance to kind of rebuild the soil pretty quickly… once you start building up that whole underground bunch of living organisms, they do that for you. And different crops exude different types of secretions from the roots.” He credits glomalin, which has been called “soil’s super glue”, for helping to bind together clusters of soil on his farm. Glomalin is a sticky protein produced by certain fungi in plant roots, which clumps together particles of soil and coats their surface. This clumpier soil can retain water longer and helps to sequester carbon.

Genetic manipulation can build on the beneficial properties of these microorganisms. For instance, scientists have also been able to isolate certain soil-dwelling bacterial species that produce toxins fatal to insects, such as Bacillus thuringiensis (Bt). Though genetically modified plants remain controversial in some areas, Cuevas argues that “biopesticides generally tend to be specific toward their target, do not leave toxic residues, reduce the risk of resistance development in the target species, and produce a lesser overall impact on the environment than traditional problematic chemical pesticides” when used inappropriately.

More generally, diversity of plant species and diversity of microbial species feed each other. Lee Farms traditionally grew flax, wheat and barley. But the Overbys have expanded the crop range. The commodity crops now include sunflowers, field peas and oats (the farm has been working with multinational food company General Mills on its regenerative agriculture program). 

The cover crops include plants like radishes, lentils and buckwheat, although the Overbys don’t always have the time and labour power to plant these. They’re continuing to experiment, by planting prairie strips – parcels of varied vegetation alongside rows of crops. And they’re thinking about planting pollinator strips – lengths of wildflowers alongside crops. 

“Having a lot of diversity, including the cover crops, it built up the soil much faster,” Overby says. It took them about a decade to see the benefits reach the lower layers of the soil, which eventually became more porous and absorptive, so that they didn’t have large wet patches sitting on the ground or running off in wet years. 

He says that embracing varied life forms is essential for farmers like him. “You can no-till and still degrade your soil. You need to have diversity in it to truly build up your soil over time.”
 
While tired soils can be seen and felt, it takes more analysis to know exactly what kinds of nutrients and microorganisms are missing from soil. This is why soil testing is paramount, Rurangwa says, and laboratories in under-resourced countries need more equipment and more training to carry out soil testing. “It’s like a human being when you go to the doctor. He can’t give you a product before he makes some tests to see what illness you have,” he says. 

Ultimately soil health is in the best interests of everyone, not only farmers. In wealthy countries where labour costs and technological resources are high, the “restoration economy” has attracted a number of innovators. These use tools like drone-based analysis of soil conditions to ensure that the trees they plant have the best shot at a long life.

Land Life Company, based in Amsterdam, primarily works on soils that are degraded past the point of immediate agricultural use. Theirs is a high-tech model of tree planting, recognising that planting trees is costly and the trees often die young. “Despite people’s best intentions, there’s no greater way to kill a tree than to have a volunteer plant it, as it is really easy to damage the tree during planting,” says Rebekah Braswell, the chief commercial officer of Land Life Company. She refers to “the two ends of the spectrum: we found a lot of examples of people crossing their fingers and kind of hoping for the best, or taking the other side of the spectrum where they were irrigating the wilderness, trying to make sure that those trees survived”.

Instead, Land Life Company collects as much data as possible to optimise restoration, such as by geotagging trees, then monitoring their health via drones and eventually satellites. They’re also developing machine learning algorithms to determine the best forms of tree care. “I think planting automation has huge potential to increase the scale of nature restoration,” Braswell says. She reports that these methods have led to decreased resource consumption and increased survival rates over three years, although more tracking will be needed to assess the long-term impacts.

The Overbys have been using smaller-scale versions of these techniques for years. They’ve divided their land into zones of 5-22 acres to allow for more targeted attention. A vendor of satellite imagery happened to live near them some years ago, so they’ve used such imaging along with soil tests to monitor changes in, for instance, soil organic matter over time. 

But some of the biggest benefits are hard to quantify. Paul Overby says that since moving to regenerative agriculture, he’s been seeing more diversity of insects, birds and mammals. The soil can’t be isolated from other parts of a healthy ecosystem, he believes. And while some farmers might not welcome seeing moose on their farmland, he’s been enjoying the flourishing of life. “What’s the value of being able to watch a pheasant from your backyard?” he muses. “Some things, there’s no price tag for.”


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