Farming 101: How do farmers estimate their corn yields before harvest?

If you drive around the countryside this time of the year (mid August) you will find number of farms with their shed doors open, some farm machinery sitting around the yard, and farmers busily prepping for the coming harvest.  Our farm is no different.  For the last few weeks we have been taking steps to prep for this years harvest.  (You can follow many farmers harvest on twitter with the #harvest14 hashtag.)

One of the most important things we do this time of the year is to create yield estimations of our corn fields.  This is very important, and gives us a good idea about what yields to expect in our fields at harvest.  By having the estimates we can develop a “Plan A” for #harvest14 which will determine how many acres worth of corn we can store in our bins, how many acres of corn we will need to haul to the grain elevator straight from the fields and how much LP (liquid propane) we will have to purchase to dry the corn we store in our bins.  While the estimates are just that, estimates, they help provide us with a pretty accurate guess as to how many bushels per acre in our fields.


Corn picked and labeled from various fields

Corn picked and labeled from various fields

Here is how we do a corn yield estimate:

Conducting a corn yield estimate is actually fairly simple, and if you have any sweetcorn handy, you can do this too!   We start by picking a handful of sample ears from a few fields, label them by field name with a marker to keep them separate from the other fields corn.  Yields can vary from field to field and corn hybrid to corn hybrid, so we try to be as thorough as we can when picking the sample ears and keeping them separate.

 When we go into a field to grab ears, naturally we are drawn to the large ears.  Its hard not to pick the best looking ears out there, but that’s not what we are after.  We want to pick ears that are a good representative of the field.  To do so we choose the ears at “random” from at least 2 different areas in the field.

We first choose an area of the field  that looks “average” meaning it’s not the best spot in the field, but it’s not the worst either.  After choosing those areas, we enter the fields, walk at least 100 feet into the fields and find a row or two that again, qualify to be considered “average”.    Now comes the hard part, avoiding picking those nice LARGE ears that you naturally get drawn to.  To avoid doing so, we literally close our eyes and take a few steps forward, feeling for an ear.  When we touch an ear, we pick it, then take a few more steps and pick another, then another.  Generally speaking, we take 2-3 ears from each area we walk into.  This “random” picking of a few ears in multiple areas in the field gives us a decent representation of what the entire fields ears may look like.

While in the same area, we also need to determine now many ears per acre there are.  To do so, we measure 17.5′ long (1/1000th of an acre using 30″ wide rows) and count every ear in that length.  While picking these areas, we found the average number of ears to be 32.  So we multiply 32 by 1000 to get, 32000,  the overall ear population in one acre. (this is important for later)

Ears picked from a 100 ac field of 105 day #2 Yellow Field Corn

Ears picked from a 100 ac field of 105 day #2 Yellow Field Corn

After we pick and label the corn, we take it to the shop to be husked and counted using a simple formula to estimate their potential yield.

Here is how:

Take an ear of corn and simply count how many kernels it has on it.  Simple right?  That may take a while.  Instead of counting every kernel, we simply count how many rows of kernels (Around)  there are on the ear and write that number down.

AG FACT:  A ear of corn will ALWAYS have an even number of rows around on it.  Usually ranging from 14-18.

After you have the number of rows around, we now need to count the number of kernels long.  Starting at the bottom end of the ear, and omitting the last few kernels on the bottom and top, count the number of kernels in one row long.  These numbers usually range from 28-42.  We do this for each ear, then average them all together.


Here is an example of how the estimates work.

Lets say you have 5 ears, after counting them all up, you come up with:

36 kernels long on average

16 rows around on average

and had the 32000 ear population stated above.

So: 36 x 18 x 32000 = 18,432,000 kernels of corn in one acre

From here we need to turn those kernels into bushels.  Normally, a bushel of corn weighs around 56lb and can contain anywhere from 75,000 to 90,000 kernels.  In order to keep our yield estimates on the conservative side, we will use the 90,000 figure, keeping our estimates lower.

18,432,000 / 90000 =  204.8 bushels per acre

Here is an example from our fields taken yesterday:  NOTE:  This particular variety has larger kernels than normal so we also conducted an estimate using a 80000 kernels per bushel figure.

Ears picked, and estimated from our field on 8/19/14

Ears picked from our field on 8/19/14.  This field has some wind damage causing the ears to be smaller than normal.

This group of ears averaged 36.3 long x 15.3333333333 around x 32000 ear population = 17,811,200

17,811,200 / 90,000 = 197.90 bushels per acre

17,811,200 / 80,000 = 222.64 bushels per acre

Although the combine will tell us what the yields really are, now that we have some basic yield estimates we can make a plan to haul the correct amount of bushels to our bin sites or the grain elevator for storage during harvest.   

The next time you have corn on the cob for dinner, you can do the exact same yield estimate on your ear as we did here to see what it could have yielded if harvested like field corn would be.

Have any questions or comments?  I would like to hear from you!  Please comment below!  I look forward to talking with you!

10 thoughts on “Farming 101: How do farmers estimate their corn yields before harvest?

  1. In the world of scrap metal, we have a somewhat unusual situation. We can look up the commodity price, but local scrap buyers generally only purchase at 1/3 the commodity price. For instance, lead is trading at $1.01/lb today. If I brought some lead in to sell to my scrap buyer, they would pay me 33 cents/lb, and I’ve found that buyers around town here can fluctuate over 10% (in this case, ~10 cents) above or, usually, below the “one-third” rule at their whim. Perhaps the local scrap buyer turns around and has to sell at commodity price to the regional buyers.

    But when you go to sell your grain (where do you sell it — a grain silo?) you get the Chicago Board of Trade commodity price as it’s being traded that day, or a price that you agreed to in the past, or what?


    • We have a very similar situation to yours. Our prices are always based off of the CBOT trading prices but the grain elevators, ethanol plants, soybean processors etc that we sell to have their own prices which are often 10-25 cents per bushel lower than the CBOT price. It all depends on supply and demand, just like the metal price does. We also have the option to sell grain early promising to deliver it at a certain time. Basically, we could sell corn for a promised delivery in December, using the CBOT Price. The grain elevator then adds or subtracts (usually subtracts) from that price to allow them to make a profit as well.


  2. If you were able to sell your corn in September, what price would you get? It looks like CBOT Sept 2014 corn is valued at between $5 and $6 per bushel ($5.4250/bu as of Aug 18). So a harvest of 200 bushels per acre might mean $1000-$1200/acre in revenue for you? Or is your price determined in a different way?


    • I wish it was that much income in reality. Here are our local cash bids (what we actually get paid by grain elevators) as of today at 1030am:
      C aug4 3.63
      C oct4 3.4175
      C jan5 3.60
      S FHA4 13.0275
      S Oct4 10.2775
      S dec4 10.4075

      We also need to be mindful that we need to subtract storage, (20cents) trucking (9-15cents) and drying (15-25cents) per bushel from that price. So if we sell in January for example, we could actually get a $3 price ($600/AC) before any of our input expenses are taken into account. Farming is not a get rich quick career by any means. It’s the biggest gamble of our lives.


      • Nice, thanks for the insight. I’m now reading the CBOT C price correctly in the neighborhood of $3.50… Can you say what your net income might be this year? I’ve read that in the early 2000s breaking even or making $10-$30/acre was normal, whereas a couple years ago corn netted $100-$200 or more per acre. That’s a pretty big fluctuation, though we’ve seen similar ups and downs in metal prices (steel, copper, brass, aluminum, lead) over the past 10+ years.


      • At this point our income is completely up to mother nature. Yields can vary considerably as we go through hot spells, dry spells, humidity that can bring on plant diseases etc. The one thing I can tell you for sure is that overall farm income will be down considerably for the overwhelming majority of farmers. Some may even farm for a loss next year if the current prices stay the way they are now. If you take 200bu corn at $4, thats $800 per acre income. Subtract land rent, which can vary from 180-450/acre and you take a good chunk of that away. Take another $300 and up or input costs, machinery costs, interest, labor, etc and your $800 is gone. Keep in mind, I have yet to add in cost of living expenses. There are times where a big crop, does not equal big income, and this year is one of them. Hopefully next years prices will be more favorable.


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