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Core Ideas Analysis of 748,374 yield records showed a 4.3% yield penalty for continuous corn. Corn yield penalties were more severe in areas with low moisture and low yields. Continuous soybean showed a 10.3% yield penalty, worse in low‐yielding years. Corn yield penalties grew with up to 3 yr of continuous cropping, but not more. Soybean penalties increased monotonically with number of years continuously cropped. The effects of crop rotations on yields have historically been assessed with field trials, but new datasets offer an opportunity to evaluate these effects using data from commercial farmers’ fields. Here we develop a unique dataset of 748,374 joint observations of field‐level yields, crop histories, and soil and weather conditions across the U.S. Midwest to empirically evaluate crop rotations. For rainfed fields, we found an average continuous corn (Zea mays L.) yield penalty (CCYP) of 4.3% and continuous soybean [Glycine max (L.) Merr.] yield penalty (CSYP) of 10.3% during the 2007 to 2012 growing seasons. The CCYP is greater in locations with low moisture, while the CSYP shows the opposite pattern. Relatedly, irrigation decreases the CCYP but not the CSYP. Both penalties increased with the number of years a field had been continuously cropped, and while the CCYP leveled off after 3 yr in corn, the CSYP showed significant increases out to the (very rare) 5‐yr continuous soybean sequence. An analysis of weather, soil, and planting date interactions with the CCYP and CSYP suggests that timely planting, favorable soil‐climate, and warm early and late‐season minimum temperatures correlate with reductions in the CCYP, while dry conditions and less favorable soil‐climate correlate with reductions in the CSYP. The results of this study not only help refine estimates of rotation effects in commercial fields, but also shed light on the relationships between rotation effects and other factors, thereby offering insight into potential causal mechanisms.

Supplementary material for this article is available online Corrigendum AbstractThe original raw dataset used to generate this work contained a number of duplicate entries-roughly 7% of the total farm fields. The substantive majority of these were from one large farm that had conducted their operations in a way that caused duplication as a side effect in our data generation process. Unfortunately, as the error was in the raw dataset, its correction required a re-run of the entire data pipeline, resulting in numerous small downstream changes. With respect to the most important numbers, the accuracy of the classifier went down slightly from 91.5% to 91.2% measured in absolute terms but increased from 0.68 to 0.74 measured by kappa. The trend in cover cropped acres grew slightly stronger, and the yield effects in maize and soybean moved from 0.65% to 0.71% and 0.35% to 0.29% respectively. None of the overall conclusions of the work have materially changed. Below, we provide all changes to the applicable sections of the original manuscript in bold underscore (or strikethrough) where applicable, in addition to modified versions of the corresponding figures and supplementary materials. OPEN ACCESS RECEIVED AbstractThe practice of planting winter cover crops has seen renewed interest as a solution to environmental issues with the modern maize-and soybean-dominated row crop production system of the US Midwest. We examine whether cover cropping patterns can be assessed at scale using publicly available satellite data, creating a classifier with 91.5% accuracy (.68 kappa). We then use this classifier to examine spatial and temporal trends in cover crop occurrence on maize and soybean fields in the Midwest since 2008, finding that despite increased talk about and funding for cover crops as well as a 94% increase in cover crop acres planted from 2008-2016, increases in winter vegetation have been more modest. Finally, we combine cover cropping with satellite-predicted yields, finding that cover crops are associated with low relative maize and soybean production and poor soil quality, consistent with farmers adopting the practice on fields most in need of purported cover crop benefits. When controlling for invariant soil quality using a panel regression model, we find modest benefits of cover cropping, with average yield increases of 0.65% for maize and 0.35% for soybean. Given these slight impacts on yields, greater incentives or reduced costs of implementation are needed to increase adoption of this practice for the majority of maize and soybean acres in the US.

In adapting US agriculture to the climate of the 21st century, a key unknown is whether cropping frequency may increase, helping to offset projected negative yield impacts in major production regions. Combining daily weather data and crop phenology models, we find that cultivated area in the US suited to dryland winter wheat-soybeans, the most common double crop (DC) system, increased by up to 28% from 1988 to 2012. Changes in the observed distribution of DC area over the same period agree well with this suitability increase, evidence consistent with climate change playing a role in recent DC expansion in phenologically constrained states. We then apply the model to projections of future climate under the RCP45 and RCP85 scenarios and estimate an additional 126-239% increase, respectively, in DC area. Sensitivity tests reveal that in most instances, increases in mean temperature are more important than delays in fall freeze in driving increased DC suitability. The results suggest that climate change will relieve phenological constraints on wheat-soy DC systems over much of the United States, though it should be recognized that impacts on corn and soybean yields in this region are expected to be negative and larger in magnitude than the 0.4-0.75% per decade benefits we estimate here for double cropping.