Importance of Timing Emergence

It is well known and documented that non-uniform stands in corn can lead to yield loss. Research has validated corn plants varying 2 leaf collars or more will experience a yield penalty. However, in recent years, messaging has arisen that emergence differences by 12, 24, 48 hours or more can lead to significant losses in yield.  Statements like this are misleading. It is more accurate to discuss non-uniform emergence in terms of growth stage differences in corn rather than time differences in emergence.

Many factors can influence temporal differences in emergence. Some may be very transient (short-lived) and inconsequential like slight variations in soil residue, soil moisture, soil temperature, seed orientation, or seeding depth. Other influencers of delayed emergence may be longer lasting and impactful like compaction or damage from pest or pathogens. It is impossible to know at emergence what the causes of temporal emergence may be and the degree of their consequence. Furthermore, timing of emergence and growth is strongly influenced by heat units. Depending on the weather, a 24- or 48-hour emergence delay could be 20 or possibly even 30 GDDs when planted into warm soils. However, in cooler conditions, a 24- or 48-hour emergence difference may equate to 5 or 10 GDDs. This also highlights why discussing emergence uniformity in terms of time is misleading. 

It is important to incorporate management practices that minimize stand non-uniformity. These things can include planting into proper soil conditions, maintaining consistent seed spacing, minimizing doubles and skips, planting at the proper depth, and including inputs to enhance emergence like fertilizer (zinc), insecticides, or PGRs. However, focusing too much on uniform timing (i.e. “within ___ hours of each other”) is exaggerating the truth.

Click here for a University of Illinois article on the subject.