Scientists have dedicated many decades and resources to studying the effects of tillage on soil properties and crop yields. However, the literature lacks empirical data on corn/soybean yields and their stability to variable-weather years under long-term management at multiple locations in mid-Western USA. Thus, the objective of the current study was to evaluate yields and their stability from 2009 through 2013 at eight long-term sites with no-till (NT) and chisel-plow (CP) managed continuous corn (CC) and corn (Zea mays)-soybean (Glycine max) rotations (C-s and c-S for corn and soybean phase). The tillage-treatment durations among the eight sites ranged from eight to 51 years in the Midwestern U.S. Corn Belt. The data indicates that tillage had no significant effect on long-term crop yields, with a few exceptions. During one site-year (southern Minnesota in 2012) in the CC system, NT yielded significantly 15.2% more than CP (9.1 vs. 7.9Mgha-1). However, CC yields averaged across sites were significantly 10.5 and 13.6% more in CP than NT in 2009 and 2010, respectively (12.6 vs. 11.4Mgha-1in 2009; 12.5 vs. 11.0Mgha-1in 2010). In the corn-soybean rotations, CP yielded significantly 18.7% more than NT (12.7 vs. 10.7Mgha-1) when averaged across years at one site in Iowa for the C-s phase. Yield stability indexes to environmental conditions indicated no differences in NT than CP yield stabilities among variable-weather years. However, NT had significantly lower range of relative yields across the variable-weather years as compared to CP for the CC system and C-s phase. These direct and synthesized data provide evidence of little to no differences between CP and NT managed corn/soybean research plots exist in the Midwestern US. Although CP may produce greater yields when averaged across the region's research plots during some years, this effect was not evident at the individual research plot scale.
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