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.”