For the past several decades, farmers have been abandoning their plows in favor of a practice known as no-till agriculture. Today, about one-third of U.S. farmers are no longer tilling their fields, and still more are practicing conservation tillage—using equipment that only disturbs the soil to a minimal degree.
No-till and, to a lesser degree, conservation tillage maintains or improves soil quality by preserving soil structure and moisture, increasing soil organic matter, and providing habitat for soil microbes.
As it turns out, it’s the microbes that matter most.
“Soil microbes are the workhorses of the soil. They break down crop residues and release nitrogen, phosphorus, potassium, and other nutrients back to the soil so they’re plant-available. We want a healthy, diverse microbial community so that those processes can happen and improve our soils,” says University of Illinois doctoral student Stacy Zuber.
Until now, most studies linking tillage intensity and microbial activity have been done at the scale of individual farms. Most of these studies do find more soil microbes with no-till management, but the magnitude of that result varies a lot from farm to farm, and with differing environmental factors, agronomic practices and soil types.
Zuber wanted to cut through the confusion to detect a true “signal” of the effect of tillage on soil microbes. To do that, she compiled and analyzed data from 62 studies from all across the globe.
“When you’re doing individual field experiments—even if you have several in one area—you’re still focused on the one region,” Zuber notes. “Sometimes it’s hard to see the big picture because there’s so much variability.”
When the data from all 62 studies were analyzed together, it turned out that microbial biomass and enzymatic activity were greater in no-till than in tilled systems. In tilled systems, the type of tillage equipment mattered. In contrast to other tillage equipment, such as moldboard plows or disc plows, the use of chisel plows was associated with greater microbial biomass. Chisel plows, which theoretically result in minimal soil disturbance, are commonly used as part of a conservation tillage system.
But experimental use of a chisel plow, as represented in the studies Zuber analyzed, may be different from how they are used in the real world.
“Tillage seems simple: you break up the soil or you don’t. Things get complicated when you start looking at tillage implements, because there is no clear definition and common use for them. You can have two implements called chisel plows, but they can work the soil completely differently. For example, if they go across the field in one pass, that’s not much disturbance. But if they make two or three passes, it’s a lot more disruptive,” Zuber explains.
The study suggests that since soil microbial biomass and enzymatic activity can stand in as proxies for soil quality, farmers should consider moving toward no-till or conservation tillage systems.
Zuber says, “Helping the soil function better helps your crops grow better, and can also maintain high quality soil for sustainability purposes. In Illinois, we have such great soil; it’s our biggest resource. Farmers can help protect it by making sure the microbial community is healthy.”
For more information on University of Illinois Extension programming in Coles, Cumberland, Douglas, Moultrie and Shelby counties, visit our website at http://web.extension.illinois.edu/ccdms/index.html or call us at (217)345-7034.