191-11 Crop Rotation Diversity and Yield Resilience: Evidence from 11 Long-Term Experiments in North America across a Precipitation Gradient.
Historical data from 11 long-term grain-based experiments comparing crop rotational diversity that comprise over 300 site-years were obtained. Data include rotations from one to five cash or cover crops and spanned a precipitation gradient from ~400 to ~1100 mm MAP. The objectives were to determine the extent to which more diverse rotations reduce corn yield losses in stressful years, and to determine whether corn yields increase more rapidly over time in more diverse rotations. Hierarchical Bayesian statistical approaches were used to assess these multilevel and longitudinal data. While yield responses to crop rotational diversity vary across sites, the overall response shows that crop rotation diversity provides increased yields in stressful conditions, takes better advantage of favorable conditions, and accelerates yield gains over time. This approach shows the potential of cross-site, large-scale synthesis to reveal foundational knowledge of agricultural production systems, which complement locally-applicable results. Synthesis efforts should increase as long-term agricultural experiment networks and databases that make historical data more accessible are established.