With renewed interested in planting corn comes additional corn-on-corn acres.  The continuous corn yield penalty is a well know phenomenon, however, why the penalty exists is not well understood.  Research at the Illinois State University identified three main factors which may help when positioning fields for corn-on-corn acres.

Common belief in the countryside is that the continuous corn yield penalty stabilizes over time.  Researchers at Illinois found the yield penalty escalated annually for seven years.  Researchers also found that management factors such as incorporating residue, additional nitrogen fertilizer, use of corn traits and fungicide applications improved continuous corn yield versus not incorporating these strategies, however, corn yield remained significantly lower compared to corn in rotation. 

The most significant factor to reducing the yield penalty was the soil’s ability to mineralize/immobilize nitrogen.  Research showed that the smaller the difference in corn yield between well supplied nitrogen and zero nitrogen, the lower the continuous corn penalty.  To put it practically, the more stable corn yields are in a given field over time (years), the higher the probability the soil is mineralizing adequate nitrogen for the crop.  Mineralized nitrogen was a key factor due to the slow release of the nutrient over time, resulting in more availability later in the crop season matching crop demand.

The residual accumulation over time of corn stover was a smaller significant factor in the continuous corn yield penalty.  When 30% of the stover was physically removed from the field following harvest, corn yields rebounded to be similar to rotated corn yield.  Removing stover is not an option for most; however, if silage corn is included in the rotation, it may be prudent to plant first year corn as the silage crop and second year corn as grain.  Another option may be limiting the years a field is in corn to manage stover, knowing continuous corn yields decline annually.  Simply incorporating corn stover did not significantly affect the magnitude of the yield penalty in the following corn crop.

The third factor influencing the magnitude of the continuous corn yield penalty was weather.  Simply put, if weather during critical growth stages is favourable for the corn crop, the yield difference in continuous corn was comparable to corn in rotation.  However, if the growing environment was negative for corn yield, the continuous corn yield penalty was significantly larger in comparison to rotation.

The continuous corn yield penalty can be managed.  Cropping plans which factor in the resiliency of soil to stress, limit the number of years in corn and identify the soil’s ability to mineralize nitrogen can reduce the yield penalty.  However, it is important to note that each year the factors affecting the corn yield penalty vary in magnitude and there is no silver bullet approach.

Source: Agronomy Journal 105:2:2013 – Identifying Factors Controlling the Continuous Corn Yield Penalty

Shawn Winter, CCA-ON, Maizex Seeds Product Development Manager
Twitter: @SWinter_Maiz