As corn yields continue to increase, it is important to look at how we manage our cropping systems.  Some changes to an existing high yielding system could help to maintain current yields and increase yields to maximize your corn’s true genetic potential.  

In theory, a bag of corn has the potential to produce 470 bu/ac before it is opened (Tollenaar et al 2001). Once the bag is opened the yield reductions begin to occur based on environmental factors such as:  poor fertility, poor planter maintenance, pests , poor soil health, and the list goes on and on.  

In this article we will focus on the management of plant densities (seeding rates) in high yielding environments, and how the following two factors must be considered when deciding to increase plant densities:  

• Hybrid Selection

• Fertility Increase Management (micronutrients).

 According to Bender et al 2013, advances in plant breeding, biotechnology, and crop management have resulted in increased average corn yields.  With these advancements in corn breeding, breeders have created hybrids that physically and agronomically respond to increased plant densities, and as populations are increased, both macronutrient (N, P, K, Ca, Mg) and micronutrient (Zn, Mn, Cu, B) intake increases (Ciampitti et al 2013). 

Hybrid Selection:

Hybrid selection is the first and most important decision made when increasing plant densities.  Fasoula et al 2004 stated that when selecting a hybrid for higher plant densities it should have two components:  Tolerance to stress and the ability to exploit added inputs. If these two factors are not considered, then there is an increased risk of a negative yield response when planting densities are increased.   

One more factor that should be considered is the ability for the cob to ‘flex’. A hybrid with a flex cob does not respond to higher planting densities because its upper yield potential is gained by the cob’s ability to flex longer under standard plant densities (32,000 plants/ac).

By contrast, a hybrid with a ‘fixed’ or ‘semi-fle’ cob; partnered with stress tolerance and the ability to exploit added inputs (strong roots) will respond to higher plant densities (34,000-36,000 plants/ac). The increased yield response can be attributed to the plant’s ability to produce the same size of cob under low, medium and high planting densities.

The following is a comparison between two hybrids to help emphasize the importance of hybrid selection when increasing plant densities. As you can see in Table 1 the two selected hybrids are similar in maturity ratings, and stalk strength.