Corn School: Protect cob row numbers for highest yield potential


How important is the number of rows on a corn cob? When row numbers shrink from 20 to 18 you could be looking at a 20-bushel per acre yield loss, says Illinois-based BASF agronomist Jeremy Hogan.

On this edition of RealAgriculture’s Corn School, Hogan breaks down four components of yield – protecting row numbers, maximizing ear count, kernel count, and seed size and weight.

Hogan says the key to ensuring high row numbers is to manage plant stress at the V5 and V6 plant stage. Quite often evidence of these stresses can be seen on the corn cob. Extra rows can be observed at the butt of the cob but the rows converge to create fewer rows further up the cob. These staggered rows are often the product of environmental conditions – the arrival of a cold weather snap, for example – but they are also the product of stresses that growers can control.

In many cases, tillage layers can prevent plant roots from pushing down into the soil to pull out nutrients and moisture. The plant senses this challenge and reduces the number of rows it will set.

Weed pressure can have the same impact. “I’ve seen situations where we didn’t put down a good, strong residual herbicide and we get to the V4 or V5 stage and those young corn plants are competing with these weeds and the plant senses that and goes from 18 (rows) down to 16,” Hogan explains.  “The plants says ‘I just can’t hold on to that many rows if I have to compete with these weeds’.”

Soil density is another factor that reduces row numbers, says Hogan. “Most farmers probably don’t realize where that density layer changes from the A horizon to the B horizon. If there is a density layer in there that’s natural then how do we incorporate those two layers and make a smoother transition for the root when it does get to that layer?”

See related: Boost kernel size for more yield

Hogan says soil density issues can also be compounded by tillage passes in the spring when the soil is unfit. This creates tillage layers that can stop roots and force them to grow horizontally, restricting moisture and nutrient uptake at critical periods.

Hogan also discusses the need to prevent immobilization of nutrients. “If we have immobilization happen at the wrong time, we could have a stagger in the rows, reducing overall yield potential.” He adds “it’s important to make sure that we have nitrogen, sulphur and phosphorous right there at that young corn plant’s root mass.”

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