Understanding the Effect of Dry Planting Conditions On Potential Corn Yield: A Modeling Study.

Abnormally dry conditions during the fall of 2011 and winter of 2012 concerned Iowa farmers and agronomists.  Many asked, “What if the corn seed bed is still dry at planting?” Reduced seeding rates and earlier hybrid maturities were possible changes in management practices that could mitigate risks associated with planting into dry seedbeds.  The corn model, Hybrid-Maize, allows users to alter seeding rate and hybrid maturity with different soil moisture contents at planting. The objective of this study was to compare the effects of seeding rate and hybrid maturity changes with normal (100% field capacity) and dry (50% field capacity) seed beds at planting on yield. The intention was to help farmers with planting decisions.  A unique facet was that the model simulated conditions  never experienced on a broad scale in Iowa.  Five locations were simulated.  With no management changes, dry soils at planting reduced simulated yields from 2 to 25% depending on the location.  Early-season hybrids (100 heat units earlier than ‘full-season’ hybrids) improved yields in more than half the years at one location but in as few as 13% of the years at another.  Plant populations - reduced by 5000 plants per acre compared to ‘normal’ populations – did not improve yields in any year at some locations but up to a third of the time at other locations.  The simulations with drier soil moisture conditions always resulted in more years in which the scaling back of management increased yields.  However, the risks of lower yields associated with the management changes outweighed potential gains.  Farmers likely did not alter their approaches to either hybrid selection or seeding rates in 2012.