It’s always a little disappointing when you see the educational institutions who are supposed to be enlightened and progressive fall into the tillage trap again — much less promote it to farmers.
But that’s exactly what happened last month:
- On Jan. 21, University of Nebraska Extension carried an article, “Strategic Tillage for the Improvement of No-Till Cropping Systems,” that concluded that occasional tillage might be OK every 5-10 years for integrated weed management, fracturing a compaction layer, incorporating a soil amendment such as lime or manure, reducing vertical stratification of nutrient availability, increasing soil organic matter to greater depth, or reducing crop residue accumulation.
- Three days earlier, the Hays (Kan.) Post penned a story “Limited Tilling Found to Produce Crop Benefits.” Bob Gillen, head of the Kansas State University’s Western Kansas Agricultural Research Center, is quoted as saying some tillage may be necessary to control herbicide-resistant, tough-to-kill weeds that have emerged. The article shares no links or data from whichever study he is referencing. “We want the no-till benefits (of no-till), but we can’t figure out how to control all the weeds, without doing some tillage,” he says.
Let’s take the Kansas article first. I have talked to a few no-tillers the last few years who’ve had to till a field to eradicate weeds that were herbicide resistant and got away from them, with kochia or Palmer amaranth often being the culprit. One farmer told me he couldn’t stand the thought of hauling out a tillage tool, so he asked his father to do it. Nobody likes to see that happen.
But there’s also no discussion in this article about the weed seed bank or what weeds seeds possibly will be stirred up to germinate with tillage. And what about the effect of tillage on all-important moisture reserves in semi-arid areas?
There is an assumption, also, that no-till systems and herbicides are to blame for weed issues, when timely field management is also an issue. Particularly with kochia, it’s important to get the sprayer rolling early.
The Nebraska article discussed a 5-year study at the High Plains Agricultural Laboratory (HPAL) near Sydney, Neb., using moldboard plow tillage, and three 5-year trials in eastern Nebraska in which five occasional tillage (OT) practices were compared. The university says multi-year trials in Australia, Brazil, Canada, Spain, and Turkey, as well as in Indiana, Kansas, Kentucky, Oregon, Texas, and Wyoming have also been done.
The effect of OT on crop yields was evaluated for 2 or more years in 35 trials globally with no effect in 72% of the cases, decreased yield in 7% of the cases, and increased yield in 21% of the cases, the article says.
“Overall, most soils are resilient to any negative effects of OT if erosion is controlled,” the article concludes. “The practice of OT once in 5 to 10 years or more is not likely to adversely affect no-till systems. However, to be beneficial the OT has to be well-planned and implemented to target a well-characterized problem such as a weed control or a compaction problem.”
I wouldn’t judge someone who has to disc or chisel plow a field when they have no other choice. But advocates for this approach who are citing research ought to be honest about all the pros and cons for hitting “reset” in this manner, and mention alternatives as well.
Tighter plant canopies, cover crops, or better crop rotation that allows for different herbicides to enter the picture are also viable methods to preventing weeds, rather than breaking out the iron as a reactive measure.