Field-scale experiments reveal persistent yield gaps in low-input and organic cropping systems

  1. Alexandra N. Kravchenko
  2. Sieglinde S. Snapp
  3. G. Philip Robertson

http://www.pnas.org/content/114/5/926.abstract

Proceedings of the National Academy of Sciences of the United States of America

Significance

Meeting future food needs requires a substantial increase in the yields obtained from existing cropland. Prior global analyses have suggested that these gains could come from closing yield gaps—differences between yields from small-plot research versus those in farmer fields. However, closing this gap requires knowledge of causal factors not yet identified experimentally. Results here suggest that yield gaps can be closed using farming practices that use conventional synthetic chemicals, but practices that rely more on biological management—as is the case throughout much of the developing world and in organic agriculture—require renewed attention to field-scale resource demands and place greater emphasis on the importance of field-scale experimental research.

Abstract

Knowledge of production-system performance is largely based on observations at the experimental plot scale. Although yield gaps between plot-scale and field-scale research are widely acknowledged, their extent and persistence have not been experimentally examined in a systematic manner. At a site in southwest Michigan, we conducted a 6-y experiment to test the accuracy with which plot-scale crop-yield results can inform field-scale conclusions. We compared conventional versus alternative, that is, reduced-input and biologically based–organic, management practices for a corn–soybean–wheat rotation in a randomized complete block-design experiment, using 27 commercial-size agricultural fields. Nearby plot-scale experiments (0.02-ha to 1.0-ha plots) provided a comparison of plot versus field performance. We found that plot-scale yields well matched field-scale yields for conventional management but not for alternative systems. For all three crops, at the plot scale, reduced-input and conventional managements produced similar yields; at the field scale, reduced-input yields were lower than conventional. For soybeans at the plot scale, biological and conventional managements produced similar yields; at the field scale, biological yielded less than conventional. For corn, biological management produced lower yields than conventional in both plot- and field-scale experiments. Wheat yields appeared to be less affected by the experimental scale than corn and soybean. Conventional management was more resilient to field-scale challenges than alternative practices, which were more dependent on timely management interventions; in particular, mechanical weed control. Results underscore the need for much wider adoption of field-scale experimentation when assessing new technologies and production-system performance, especially as related to closing yield gaps in organic farming and in low-resourced systems typical of much of the developing world.

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