title: Field-scale experiments reveal persistent yield gaps in low-input and organic cropping systems.
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.
authors.affiliation: Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI 48824; kravche1@msu.edu.
authors.forename: Alexandra N
authors.initials: AN
authors.lastname: Kravchenko
authors.affiliation: Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI 48824.
authors.forename: Sieglinde S
authors.initials: SS
authors.lastname: Snapp
authors.affiliation: Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI 48824.|W. K. Kellogg Biological Station, Michigan State University, Hickory Corners, MI 49060.
authors.forename: G Philip
authors.initials: GP
authors.lastname: Robertson
mesh_terms: D000383:Agriculture / Q000379:methods*; D008824:Michigan; D011891:Rain; D012987:Soil; D013025:Glycine max / Q000254:growth & development; D014908:Triticum / Q000254:growth & development; D003313:Zea mays / Q000254:growth & development
chemical_list: D012987:Soil
keywords: corn soybean wheat rotation; field experiments; organic agriculture; scaling; weed control