Fungal diseases can have a detrimental impact on soybean and corn yield. Foliar fungicides are

used to manage fungal diseases and minimize yield loss, along with cultural practices like tillage

and crop rotation. Prophylactic foliar fungicide use does not consistently increase yield for corn

and soybean, especially when disease pressures are low. Also, there are concerns about the

impact of fungicides on non-target organisms, including fungi living in the soil. We tested the

effects of tillage, crop rotation, and foliar fungicide use on corn grain and soybean seed yield

over three growing seasons. For both crops, rotation was key to achieving high yields, although

there was an interaction of tillage   crop rotation for soybean and crop rotation   fungicide for

corn. For soybean seed yield, both foliar fungicide treatments showed a small yield increase over

untreated plots. Additionally, we assessed bulk soil fungal communities in a subset of treatments

(crop rotation and fungicide treatments in no-till plots), using ITS sequencing and PLFA-FAME.

We observed distinct fungal communities in the continuously cropped treatments, while annually

rotated communities were very similar. There was also greater overall microbial biomass and a

higher relative abundance of arbuscular mycorrhizae fungi associated with continuous corn.

There were no differences in soil fungal communities or microbial biomass associated with foliar

fungicide treatments. Based on our findings, we recommend that farmers use integrated pest

management strategies to manage fungal diseases, which may include fungicide applications, if

they are justified by economic disease thresholds or prediction tools.