A recent posting in "Weeders of the West" a WSU blog [https://smallgrains.wsu.edu/weeders-of-the-west/2021/06/21/occasional-tillage-and-herbicide-resistance/ ] stirred me to make this posting. The link above will take you to their posting that I am referencing. For about 5 years I have been hearing WSU weed scientists introduce "occasional tillage" back as a practice to reduce herbicide resistance. For those of us that are die-hard no-tillers, that's like throwing gasoline on a fire, --it makes no sense what-so-ever.
I could rant on this all day, but I will try and limit my comments to a few references in the posting. I’ll start with a statement of my position. I’m not quite as old as dirt but I was around before there were synthetic chemistry or fertilizers for our crops. I have spent most of my life stirring dirt, destroying my little portion of the Palouse ecosystem. For the last 30 years I have been trying to figure out how to repair that damage. Since the year 2000, research on soil health has grown astronomically. It's to the point where I discount (not reject) research findings that are more than 5 years old.
--What is soil health? I find that it has many different parameters depending on who is speaking on the subject. I can accept Huberto Blanco-Canqui’s findings for the high quality, deep soils that probably make up their research sites. If the soil is deep, with high OM, and a near neutral pH, then, an occasional stirring probably is a minor setback to the ecosystem. Soils with a high level of biological life have the capacity to rapidly rebuild after a destructive event. Soils with low levels of biological life do not have that capacity, so rebuilding is slow. The post mentions tillage to break up compaction and reduce stratification of soils. Back in the 70's, WSU was researching ways to mitigate tillage compaction. Compaction was recognized as a problem through the use of moldboard plows, disc harrows, and rod weeders. I had fields where four tillage pans could be identified. Chisle plows and heavy cultivators were proposed solutions. Compaction layers were found to be moving lower in the soil profile because chisels and cultivators broke soil aggregates into finer particles that moved deeper into the profile. Deep chiseling and subsoiling was considered, but rejected because it was feared that compaction layers would move lower than implements could reach. We are still dealing with compaction layers in our soils. It has been demonstrated that we can influence compaction and stratification of our soils with plants and biology. We need to figure out how to incorporate them as part of our cropping practice. There are plants and macro fauna that are very good at these tasks and leave a better long term effect. Except for small acreages, soils in the Palouse, in general, are badly degraded from erosion from years of cultivation (erosion from cultivation, water, and wind), and from being mostly a monoculture cropping system. Any cultivation is a major setback to our ecosystem. I compare "occasional tillage" to burning your house down every few years. Many of the soil biological structures don’t rebuild very quickly in our climate and cultural environment. Tillage and fallow is a real downer for soil microbe communities. Biological networks are sliced, diced, burned, starved, --and are slow to recover from a major disruption.
--What is “occasional cultivation”? I have never heard a followup explanation as to what this term meant, or how it would extend a herbicides useful life. Retracing my memory of tillage I don't think there is such a term as "occasional cultivation. Nearly every year I see a farmer do reduced tillage, and weed escapement is always a problem, which results in more tillage, or chemistry applied with less than desirable results. My experience is that tillage bury’s seed, of which some emerge and the remainder stay in the soil bank, safe, for later emergence. Tillage destroys OM and emits CO2 and H2O into the atmosphere. Tillage degrades the soil through erosion, compounding our problems. I find that, the less the disturbance, the fewer the weeds that compete with the crop. I regularly see this in my fields. A mat of surface residue along with no disturbance is preferable. I often wish my equipment could levitate over the fields leaving no track. Wheel tracks are where the weeds are. An expanded crop rotation, and rotating appropriate chemistry will be more effective than tillage in reducing herbicide resistance in weed populations.
--The ultimate goal will be removing synthetics from crop production. As time passes this will happen because of weed resistance, environmental regulation, or cost. These pressures will force us to learn to incorporate cover crops, do inter-seeding, and use companion crops in our production of cash crops.
--Disciplines within soil & crop sciences need a closer relationship. Weed scientists need to look for solutions through microbiologists, crop specialists, and other related disciplines. Books like “When Weeds Talk” by Jay L. McCaman have a lot of potential for weed management, by manipulating soil chemistry and biology through plant cultivars. Research by crop specialists working with cover crop cultivars, intercropping, and companion cropping are showing some real promise in increasing yields and reducing weed competition and diseases in cash crops. Cropping problems need to be approached through coordinated discussion and research by cooperating disciplines instead of individual disciplines reverting back to old failed practices.
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