The pic on the left represents the field with the 100+ history of tillage. The pic below (middle) represents the field with a long history of low disturbance direct-seeding. In 2020 both fields were in chemical fallow. The field in the top pic was chem fallow on spring wheat stubble. and seeded with a high disturbance drill. The field in the middle pic was chem fallow on spring canola stubble. It was seeded with a low disturbance drill.
The pic to the left (bottom) shows a part of the same fied that has a long history of conventional tillage. Shown is winter wheat stubble that is cut very short. This field is likely to be chem fallowed in 2021 and seeded to winter wheat in the fall of 2021. This stubble area is soft and mucky on the top 2" and frozen below 2", making it difficult to walk. The recent 0.29" of moisture (snow/rain) that helped thaw the surface is held in that top 2". I was able to compare this condition with a field on it's border with tall standing stubble that has a long history of low disturbance direct-seeding. That field was thawed and firm underfoot indicating that the 0.29" of moisture (snow/rain) had moved deep into the soil profile leaving the surface firm and near field capacity for moisture.
Observation: Both fields were thawed. This condition followed 10 days of hard freeze that provided ice sufficient to skate on our pond. A quick thaw followed. The field (top pic) was squishy, wet underfoot. The near-surface was well above field capacity for moisture. My loafers were mucked some when walking over the field. The field (middle pic) was firm, indicating water moved down into the profile leaving the near-surface soil near field capacity for moisture. Along with the surface armor, there was no danger of mucking up my loafers anywhere in the field. I could have driven my F150 over this field.
These field areas are close together and likely received the same weather, so what is making the difference in field conditions? Two possibilities come to mind.
1) there is no question that the soil structure is improved providing more porosity (lower bulk density) in the long term direct-seeded field compared to the long term conventionally tilled field. The slake test would easily prove that; however, in winter, with freezing or frozen conditions, soil structure with more porosity isn't the full answer.
2) There has to be a temperature factor involved. How does this factor in? Well, --there is 34 years where our direct-seeded fields have reduced or eliminated erosion compared to conventionally tilled fields. That's nearly a 1/3 of the time since native grass was removed from the landscape. That time has to have an impact on soil organic matter loss (SOM). Add to that, the time that SOM may have been building since 2010 with the introduction of our ultra-low disturbance no-till system, which includes the stripper-header, expanding our rotation to add more crop diversity, and beginning the introduction of cover crops. My bet is that we have been able to improve our "soils health" to the point that we are getting more biological activity. More biological activity results in more heat which in turn warms the ground resulting in faster frost melt, and along with increased porosity, allows moisture to enter deep into the soil profile drying down the surface soil to field capacity.
I have yet to followup by doing some simple tests, and I have missed the timing for the temperature component of my theory. My HOBO's should have been in the ground last fall and left until now. There are several simple physical in-field tests that can be done now that indicates a comparison of bulk density and soil porosity. I hope to get them done this spring/summer.
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