Doug Peterson sat under a pop-up canopy in 95 degree heat in northwest Missouri, in July to help a small group of producers, permaculture designers and homesteaders enhance their knowledge of soil health. Through demonstrations and a detailed description of soil function, Peterson advanced the group’s knowledge on how they can improve or ensure soil health in their own operation.
Peterson spoke at my farm to continue to spread the word about soil health and advance the mission of the Natural Resources Conservation Service, where he is a soil health specialist for the state of Missouri.
He began the session describing four keys to maintain and build soil health and function. “You need to disturb the soil as little as possible, keep the soil covered as much as possible, maintain a diversity of plant life and keep living root systems as long as possible,” he said.
No more tilling
Disturbing the soil can occur in several ways, Peterson explained. Tilling the soil is like a small natural disaster. What you end up with is bare compacted soil that has decreased or destroyed soil function. “Many farmers believe you need a nice fluffy seed bed to grow plants,” Peterson said. “Yet, what they are doing is creating a hostile environment in which the soil food web cannot function well.”
Healthy soil is packed with living organisms that form a food web along with plants. With hundreds of millions of bacteria, protozoa, fungi, nematodes and arthropods, an entire ecosystem exists in the topsoil that all have a role in soil function. “Tilling the soil exposes it to sunlight which vaporizes the moisture in it as well as raises the soil temperature to the point it kills off the microorganisms,” Peterson explained. “Regular tillage and cultivation also causes the soil – which is made up of particles of sand, clay, silt and organic matter – to compact and form an impermeable barrier to water which before long will run off and cause erosion.”
The particles are held together by a material (glomalin) that Peterson explained functions similar to glue holding the sand, clay and silt particles together in small clods. These clods are irregular shapes that create airspace within and between themselves that allow water and air filtration. Tilling, he said, breaks up the clods and reduces the airspace between particles.
Keep the cover on
Falling rain, hot sunshine and invasive weeds. Two of these seem like farmers’ friends while the third farmers tend to battle. But, all these things can be harmful to topsoil. “When rain falls, each drop is a little explosion when it strikes bare soil,” Peterson said. “We can slow down rain drops significantly by growing cover crops and leaving thick plant residue.”
Soil should always be covered. With a diverse mix of cover crops you gain protection over the soil that is critical. Hot sun raises soil temperatures that are detrimental to many plants, root systems and microbial soil life. “The soil microbes prefer soil temperatures from 70 to 75 degrees,” Peterson pointed out. “If we don’t keep the soil covered in cover crops or residue, the top soil temperatures get too hot for that microbial life to live.”
The other benefit of keeping the soil covered, according to Peterson, is weed suppression and moisture retention. A good thick mat of cover crop, once crimped down with a roller, is an ideal bed through which cash crops can be planted and the cover keeps the weeds from finding light. “The mat also keeps the sun from vaporizing the moisture in the topsoil.”
Polycultures equals diversity
Attracting and keeping beneficial species of animals, insects and microbial life is difficult in a monoculture. But, planting a diversity of crops and support plants – a polyculture – can create the kind of biologically diverse environment that helps create healthy soils and provides a diverse mix of the carbohydrates that the soil microbial life need to survive.
“A diversity of plant exudates is required to support a diversity of soil microorganisms,” Peterson said. “To achieve this, different plants must be grown. The key to improving soil health is ensuring that food and energy chains and webs consist of several types of plants or animals, not just one or two.”
Biodiversity is ultimately the key to the success of any agricultural system. A lack of biodiversity severely limits the potential of any cropping system and increases disease and pest problems.
Living root systems
One of the most under estimated techniques to fostering and preserving soil health and function is by keeping living roots in the soil for as long as possible. “Living plants maintain a rhizosphere, an area of concentrated microbial activity close to the root,” Peterson said. “The rhizosphere is the most active part of the soil ecosystem because it is where the most readily available food is, and where peak nutrient and water cycling occurs.”
One way to keep living roots in the soil is through cover crops – even among cash row crops. Many farmers think that competition for water and nutrients is not a good thing for their cash crops. Yet, many farmers are finding their row crops do well even when the ground is blanketed in a ground cover.
“Healthy soil is dependent upon how well the soil food web is fed,” Peterson explained. “Providing plenty of easily accessible food to soil microbes helps them cycle nutrients that plants need to grow. This has a wider effect on plants around cover crops because the soil food web is enlarged to include them.”
Managing landscapes for soil health and good soil function is a matter of maintaining suitable habitat for the myriad of creatures that comprise the soil food web. These four keys to soil health will aid any size operation no matter what stage of development.]]>