Analyzing Your Yield Map

Hunters and soil scientists may seem like an odd pairing but they have at least one thing in common – they know and appreciate that nature has an aversion to straight lines. Hunters spend a lot of time in and observing the great outdoors and getting an up-close look at the variability Mother Nature molded upon our landscape. Soil scientists not only spend time looking at the curvy contour lines that represent the transition from one soil type to another but their academic training is about the “how’s and why’s” of soil formation over the centuries.

Unlike nature, humans have figured out how to perfect designing straight lines! From early days of the very first mechanical planters and “cultivator blight”, the straightness of our rows was something that created neighborhood envy. Nowadays auto-steer has made it easy.

Straight lines are one of the first “gotcha’s” when studying a yield map. The cause for yield differences that follow straight lines are always man-made! It can be a variety change, a different nutrient application, a crop protection treatment, an equipment performance issue, a tillage pass or even something like a manure application we did years earlier. Seeing a straight line on a yield map instantly leads to digging deeper!

analyze yield data with your yield map

Yield maps are an awesome way to visualize data differences. However, a second “gotcha”, is not paying attention to the map legend! Years ago, I had a college friend send me an image of one of his yield maps, with a note that said “you see, we really don’t have much variability in our area.” But as I studied his map, I noticed that the predominant green color on his yield map had a 40-bushel-per-acre range.

use your yield data to check field variability

The two maps above use the exact same yield data.

There is not a “perfect” way to set map legends. The key is to also LOOK AT THE LEGEND – not just the map!

Use Your Data to Make Decisions

It’s almost the time of the year when making New Year’s resolutions are popular. Ever make a business resolution? If you haven’t been using your data to make decisions, how about making that your resolution?

How should you start? I’d start with your yield maps. Look carefully and hear the stories that they tell. What are some of the real-world examples of how you can use your yield map to make decisions?


1. Red circle – This one is easy, using the yield map to quantify yield losses associated with drainage issues. Up to 10 bushels per acres @$9.50/bushel = $95 per acre. The economic loss is just as severe with corn. Breakeven on running tile might be as fast as 5 years. Wonder if my land owner will work with me on solving this issue?

2. Blue circle – simple too much traffic!!! 15+ bushels less per acre – that’s $150/acre yield loss! We need a strategy to fix this! Maybe concentrated effort with a ripper and then more discipline about how we move in and out of the field?

3. Yellow rectangle – wow – between shading and competing for soil moisture, the trees in that fence row are sucking yield and money right off my balance sheet. I know the land owner wants habitat for game birds, but it comes at 10-15 bushel cost to me. Maybe showing him some of my yield maps will help in negotiating?

4. Orange circle – this i another drainage issue. I think this one is an easier fix – maybe some surface shaping and extending the waterway on the lower end.

5. Light blue circle – yikes – I remember this one – it’s my first small patch of resistant waterhemp. This is mild compared to some in the neighborhood – time to get serious.

6. Green area in NW corner – oh my – this one is a puzzle at first. Two years ago, my contract manure applicator needed a place to finish and I’m fairly sure that’s only part of the field that was knifed. This is definitely something I need to investigate – over 100 bushel per acre in many places!!!

You get the idea – your yield maps can be the first step in quantifying problems and figuring out solutions! Merry Christmas and best of luck with those New Year’s resolutions!