New perspective on tillage and speeding up soil drying in humid regions

As a young boy growing up on the farm, I enjoyed fall and spring tillage. Those days, behind the wheel of that tractor with the disk or field cultivator behind me, I felt like a respected young adult accomplishing important work; an equal and not a junior. The skill level required to do the task suited the capabilities of a young teenager… and it just felt plain awesome to command the power of the large tractors (my dad was always buying and selling farm equipment so I never had more than a couple of seasons on the same tractor). Accomplishing important work may have been the most important part, one that indicated the value to sustained farm operations that my hours pulling a chisel plower or field cultivator provided. I quickly took on the concepts or mental map used to make sense of tillage; namely that it helped speed up residue decomposition (topic for another time) but more importantly, it helped speed up soil drying in the spring so we could plant on time to make use of the short growing season northern Wisconsin affords. 

The concept was simple; expose wet soil to sun and wind to speed up drying. Conversely, delaying tillage (or skipping it entirely) meant delayed soil drying and thus, delayed planting. So, often our humid environment and significant snow melt in central Wisconsin meant we struggled with excess moisture, especially when it came to getting into the fields for spring planting. But what if we had it all wrong about tillage and speeding up soil drying in humid environments? What if the heuristic device missed some important details?

Research is now showing that in fact, we have missed a number of important details when it comes to tillage and soil moisture in humid environments. First, we missed the long-term consequences of previous management that often contributed to moisture management challenges. Tillage damages soil structure vital to moving excess water away from the planting zone while also causing surface crusting which in turn makes root growth and transpiration more difficult. Tillage also causes soil compaction or smearing, particularly in humid environments and clay soils. That compaction layer inhibits percolation of excess moisture down into the subsoil. 

So how did our assumptions feel so right but end up so wrong? Well, as with most assumptions, it starts with a partial truth that gets overgeneralized or mis-applied. Sure, exposing soil to sun and wind can speed up drying. That concept got reinforced by years of research from arid regions that conclusively proved that reducing tillage results in increased soil moisture. 

A key distinction often missed is the fact that in the sandy soils and dry environment of arid regions compaction rarely occurs and the challenge of draining excess moisture is so rare it would be welcomed. Further, when we made comparisons between tilling and no-tilling, it was almost always within a context of fields with extensive previous tilling, causing the soil moisture challenges noted above. Turns out, until recently, researchers often committed the same mistakes of missing important consequences of prior management.  

When we consider long-term consequences of prior management (namely compaction and soil structure degradation) and compare tillage to true no-till soils that have recovered from those issues, then it becomes clear that no-till is the best way to remove excess soil moisture in humid environments. Not only does no-till better remove excess soil moisture, its improved soil structure means growers can have improved field trafficability with wetter soil conditions without causing damage. I have personally experienced this advantage since implementing no-till in 2010. Thanks to better data collection and analysis, we can gain a better understanding of our soils and the practices that will give us the biggest advantage to dealing with our agronomic challenges.

By: Ryan Stockwell, Indigo Grower Engagement Senior Manager and Wisconsin farmer