Dakota Farmer

Crop Notes: Look for clues now to why yields will vary from one part of a field to another.

August 26, 2016

3 Min Read

September is a great time of year. Football is back, the weather is cooling down, hunting season is getting started and harvest is right around the corner. Maybe these are my preferences, but I think many of you can relate. One of my other favorite parts of September is evaluating my corn so I know how to improve my methods for next year.

We have a lot of technology at hand today that can help us, but putting boots in the field to get a look at the crop before harvest can fact check some of information we get from the technology.


Planting data, imagery from the summer and data from the combine can all be combined to paint the picture of your field for the year. This information is the result, but how do you find the “whys”?

Begin by getting an ear count per acre from four or five spots in your field in the same way you do a plant stand count. Ear counts can be different from stand counts, and since it’s the grain you will harvest, this information may be more useful. Ideally, you should be within 1,500 ears of your intended planting rate.

Next, check those ears for kernel rows, both around and length. You will now have your kernels per plant. Take that number times your ear count to get your kernels per acre and divide by 90,000 (average kernels per bushel, adjust for test weight differences).

Remember, ear girth is determined around V5, and ear length is determined just prior to tasseling (early to mid-July for most of you). However, environmental stresses affect ear length more than they do ear girth.

Look at the ear tips. A good way to check if you planted the correct amount of seed per acre is to take a look at the tips of the ears. Preferably, the ears should have three-fourths inch of unharvestable kernels. Ears filled to the end show that the soil had more than enough resources to support a higher population. Tip-back more than three-fourths inch shows that the plant ran out of resources and could mean more than that the population was too high. Were these lost kernels not fertilized or did they not fill due to lack of nutrition?

Investigate trouble spots. If inconsistencies are found in the field, investigate the area and note what you find to help you identify the issue. Lodging spots, stalk diameter differences (showing late emergence), insect damage and nutrient deficiency symptoms are all good indicators of yield variability and should be documented.

Knowing your fields “whys” will help you identify some “whats” this winter when looking at your yield maps.

Spelhaug is an agronomist with Peterson Farms Seed, Harwood, N.D. Follow him on Twitter at @PFSAgronomyGuy, and read his contributions to The Peterson Blog at petersonfarmsseed.com/blog. For more information, contact him at 866-481-7333 or [email protected].

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