Dear No-Till Farmer friends,
This website and its following community is a tremendous source of education for all of us. I so appreciate the articles contributed here and also the reader comments posted. Just read Mark Watson’s column, “Soil Health: It’s All About Carbon” in the March 10 edition of Dryland No-Tiller.
We all know that no-till management can never be a “one-size-fits-all” entity. No-till is just one tool in our growing toolbox to better manage our soils for crop production. It’s certainly one of the best tools, because the master of all plant production — Mother Nature — uses it!
There are other management tools also available — strip-till, minimum-till, ridge-till and vertical tillage — all with their own advantages and disadvantages. While all these “tillage” systems may address soil compaction, they all have one thing in common: macro-aggregate disturbance. Just one pass of ANY kind of tillage implement will damage macro-aggregate stability.
In a southwest Nebraska fine sandy loam soil, for instance, I’ve found just one tillage pass after 8 years of no-till management (early-spring disced following a rapid thaw — cattle were on corn stalks a little too late) changed the aggregate stability test from all aggregates remaining 80-100% stable after 5 minutes of agitation to 60% or more slaking through the screen in less than one minute, and less than 40% of sample aggregates remaining on the screen for the full 5 minutes.
I hypothesize that the aggregates that remained on the screen for the full 5 minutes weren’t disturbed by the disc pass, while those that were moved slaked in the first minute. There were no in-betweens —less than a minute or greater than 5.
Macro-aggregates allow water to infiltrate rapidly (similar to sand and gravel), but macro-aggregates are very fragile. The larger a soil aggregate, the more fragile it is. Macro-aggregates form under native vegetation, no-till, and to a much lesser degree, strip-till. You will not likely find significant macro-aggregates in conventional tillage systems in the Great Plains.
Organic carbon was low here in this example, and your results with higher organic carbon might not be so dramatic — but the point is, the stability of your soil aggregate — the HABITAT of the soil livestock is damaged and soil health is set back for years. This is especially true for the physically larger predatory livestock that eat the bacteria and fungi and release soil nitrogen (N) back into a plant-available form.
In addition, with tillage, soil carbon is rapidly lost from the system in the form of CO2 released back to the atmosphere, and surface evaporation is increased, with a big hit to your water efficiency.
If you have soils that are very wet in spring and early summer and are subject to compaction, choose high-water-use cover crops that grow in the spring and use up some of that excess moisture. Add deep tap-rooted species to your cover crop or rotational mix to punch through the compaction.
No-till will often show slight compaction in concave (receiving) areas of your fields, but this compaction isn’t necessarily detrimental if your crop roots are growing down through it without significant horizontal deflation.
Crop roots will follow the tubular paths of previous roots and earthworm channels, because those are the preferential flow paths for infiltrating water and roots will follow this water deep into the profile.
Tillage destroys infiltrating water’s access to these preferential flow paths, and if your soil is loam, silt loam or anything with higher clay amounts, your effective precipitation into the lower parts of the soil profile from rainfall and irrigation will be reduced.
Below is an educational video from Washington State University that demonstrates what I am describing with preferential flow paths.