Sustainable agriculture depends on the long-term availability of the resources needed to produce a quality product. Arguably the most important of these resources is a suitable soil/land base that can continually grow an economical crop with a sustainable yield potential.
One of the most-often written about and researched subject matter areas dealing with land and crop production is how the amount and kind of tillage will affect the soil’s characteristics that are known to affect soil health and subsequent plant growth. It is generally accepted dogma that tillage is or can be used to control weeds, incorporate crop residue, and prepare land for planting a crop. It is also generally accepted dogma that minimizing soil disturbance and maintaining soil cover are critical practices for maintaining and/or improving soil health.
Any tillage operation can and likely will affect soil properties that are desirable for optimum soil health. And this effect is most often negative; thus lack of tillage has become the preferred production practice. Click here for a White Paper that discusses the issues associated with various levels of tillage and here for a White Paper that discusses issues related to soil health.
Tillage in some form or another has been researched for decades. However, many of the tillage research projects that are often cited were of short duration because of length of tenure of the principal scientist (e.g. graduate student) or because funding for such projects was (and still is) of short duration. Thus, there was no way to accurately measure tillage effects on preferred soil processes that take many years to manifest themselves when a tillage system is changed.
An article titled “Long-term research avoids spurious and misleading trends in sustainability attributes of no-till” by Cusser et al. (Global Change Biology 2020:26:3715-3725) reports on research that delved into this issue. The title of the article succinctly defines its contents, which are summarized as follows.
• The premise for the study is that management recommendations to producers that are based on short-term studies can be misleading or even wrong. Results from many management changes can be slow to develop and detect, especially for soil attributes that are affected by a change in tillage system.
• Economic concerns are the largest barrier to adopting sustainable agricultural practices such as no-till or minimum-till systems. Many of the positive results from adoption of these systems may take a lengthy period to consistently increase yields and profits.
• The researchers analyzed results from a 29-year experimental dataset that was collected from a long-term research site in the upper Midwest to: 1) determine the time required to detect significant differences in crop yield, soil water availability, and NO2 fluxes; 2) determine the time required to recover the initial management costs of adopting a continuous no-till system; and 3) investigate the consistency of trends over time.
• This analysis involved comparing conventional till and no-till management systems in corn, soybean, and wheat cropping systems. The no-till system consisted of planting a crop into untilled soil, and had been managed without tillage since its establishment in 1989.
• Both environmental responses (soil water availability and NO2 fluxes) and relative profitability were examined over the 29-year period to determine the time required for the effects of conversion from conventional tillage to continuous no-till to be manifested.
• The analysis used (∝ = 0.05) indicated it would take at least 19 years to detect a significant and consistent positive effect of no-till on crop yield and 25 years to detect a significant positive effect of no-till on soil water availability. A more liberal analysis (∝ = 0.20) indicated that it would take 16 and 19 years, respectively, to have a significant positive effect on yield and soil water availability. There was no long-term effect of no-till on NO2 flux.
• No-till was a money loser in the early years of its adoption, but initial expenses associated with its adoption were recovered because of increased yields after 13 years of implementation at this site.
• These results suggest that analyses performed on no-till research results of less than 15 years would provide misleading results and/or trends about its positive effects. More than a decade was needed to detect the consistent benefits of continuous no-till on the economic and environmental attributes measured in this study.
• These results also show that longer periods of no-till implementation increase the likelihood that continuous no-till management will prove more profitable than conventional tillage. Periods of 3 to 10 years after no-till implementation had a significant number of years with negative profitability, while results in years 21 to 29 after its implementation were all more profitable than conventional tillage.
• These results highlight the importance of conducting no-till research on a long-term vs. short-term basis; i.e., no-till recommendations based on short-term studies can provide bogus, misleading trends because the early years of such research represent a strong disturbance to the soil ecosystem that will take many years to equilibrate.
• These results also show that continuous no-till vs. conventional-till over many years will benefit producers.
As stated above, the data used in this analysis were obtained from a location in the upper Midwestern US. Thus, there is no assumption that the absolute values cited above will be the same as those obtained from similar studies in the Midsouth. However, it is quite likely that the cited findings on duration of time (short- vs. long-term) needed to detect the positive benefits of no-till adoption will be representative of those from Midsouth studies–i.e., there is little doubt that short- vs. long-term no-till vs. conventional-till studies can or will provide misleading results no matter where the study is conducted. This is a point that funding entities–both public and private–should consider when determining whether or not to fund tillage research.
Composed by Larry G. Heatherly, June 2020, firstname.lastname@example.org