Field-specific yield response to variable seeding depth of corn in the Midwest

Sufficient soil moisture is crucial for corn (Zea mays L.) germination and emergence. As within-field soil moisture varies, it is often expected that corn seeding depth should vary accordingly. As seedbeds get drier, deeper planting increases the chances of higher soil moisture and faster emergence. The goal was to evaluate the corn yield response to shallow and deep seeding depths compared with the standard seeding depth while making use of management zones delineated using relative elevation data as surrogate of spatial patterns of soil moisture. We hypothesize that crop yield responds positively to shallow seeding depth in zones with low relative elevation values, wet zones, whereas the opposite would be expected in drier zones in a range of locations across the U.S. Midwest. Landscape position (LSP) values (i.e., relative elevation values) were computed from LIDAR data and used to approximate the spatial soil moisture distribution by splitting variability into dry, transitional, and wet LSP zones. Field-long strips were planted in 17 commercial fields in 2014 and 2015 at shallow, standard, and deep seeding depths. The LSP zones were a significant predictor of the yield response to shallow or deep seeding depth only in 5 and 2 out of 17 field-years, respectively. Significant overall responses of yield to shallow or deep seeding depth were found in 6 and 8 out of 17 field-years, respectively. The yield response to variable seeding depth of corn showed high field-specificity and was likely attenuated by favorable conditions for corn planting and during the growing seasons.