Normalized Yield Map

Last week I decided it was finally time to start using our VARIABLE RATE SEED DRIVE on our corn planter for more than just easy adjustment between seeding rates for different custom jobs.  With the seed being the by far the highest expense in our corn crop budget we need to utilize this technology.  I spent about a year and a half asking every agronomist I came across this question.

“Should the wet area’s that typically yeild low on the farm get more seed or less?”

The consensus seemed to be to reduce the population. The logic being that the investment per acre is lower and if the corn suffers from moisture stress you have less input loss in those area’s.  If conditions are good a lower population should still give an economic return in those area’s.

To implament the technology I had to do a little work.


Step 1.  I created a normalized (indexed) yield map based on multiple years of yield data. With some tweaking of the ranges of the zone we were able to come up with the following map which i can vouch for being a great representation of what the farm is like from the seat of the tractor.

Planting Prescription Map

Step 2 .  The goal is to use the normalized yield zones as a reference to create a planting prescription map assigning the desired population values to the high and low yielding areas.    So i created a planting prescription map that transferred the zones over.  I needed to convert the zones to a grid format of 30′ x 30′ to make it easier for the machine to respond and we were ready to assign seeding rate values.

Step 3 .   I have never done any trial on population on corn so I needed a little help from an expert.  I had a visit with an agronomist from Dekalb named Todd Woodhouse. To help me understand how the varieties that were going to be growing on this farm would react to different populations.  This is the rates we settled on. Thanks Todd.


Seed Rate We Settled on

Step 4.  Evaluate.  We are going to plant this farm every other pass Variable Rate and plant the balance at our normal rate.  When we take it to yield we can evaluate on a comparative basis if we are headed in the right direction with where we put high and low populations.