Four steps to help you make sense of yield data

Wednesday, October 6, 2010

Drowning in data at harvest time? Here are some approaches that will help you make sense of the masses of numbers and find the biggest potential for yield increases

by KEITH REID

With more and more combines in the field having yield monitors, I get the sense that many farmers feel they are "drowning in data" at harvest time.

In the worst cases, growers may be completely overwhelmed and give up trying to sort through the masses of numbers. They may actually end up with less useful information than their neighbour who keeps track of the loads coming out of each field with a pencil and notebook. 

The first step in overcoming data overload is recognizing that "data" is not the same as "information." The raw materials may be there, but there needs to be structure and organization applied to the data so it can be used for making decisions. The second step is to realize that not every number generated is important, or even correct, but that averaged numbers can provide useful information.

There are many ways to approach the interpretation of yield results, and the one you choose will depend on your individual strengths and preferences. We all know those people for whom juggling numbers is as natural as breathing, while most of us are more comfortable looking at a map or a graph.

I am going to suggest a step-wise approach that should allow you to pull out the most important information first, while being open-ended enough to allow more in-depth analysis for those with the skills and interest.

Step One: field averages. Looking at the average yield from each field seems so basic it is easy to overlook. These comparisons should look at how the yields vary between fields this year, as well as how yields vary within a field across the years. How do the top third differ from the bottom third? Can you point to the causes of yield differences? Are any fields performing significantly better or worse than previous years? Why?

Fields at the low end of the yield scale should be the first candidates for a closer look, since these are probably the ones with the greatest opportunity to increase yields. One important consideration, however, is how big the yield differences are between fields. A three bushel yield difference won't justify nearly as much expense to correct problems within a field as a 30-bushel yield difference. The average-yielding fields will be the next candidates for assessment.

Step Two: obvious differences within fields. The next level of detective work is to look for broad patterns of yield differences within fields, as this will provide clues to identify the causes of yield loss. Do the knolls or the hollows yield better? Are there patterns that match up with differences in soil type or field traffic? Can you see the patterns of the old field boundaries? All of these help to sort out if you should be looking for poor drainage, low soil pH or nutrient deficiencies.

Step Three: follow up with field measurements. Confirm your suspicions of the causes of poor yielding areas by walking the fields, probing for compaction or excess moisture, or collecting samples to analyze for nutrient and soil pH levels. A small investment here will ensure that larger investments are made properly.Step Four: correct the problems that will give the biggest payback. Few farmers have the resources to solve all of the potential problems at once, but the numbers provided by a yield monitor can help to identify the areas with the biggest potential for increases in yields and net returns.

As the most serious issues are dealt with (and sometimes the solution is to walk away from that property completely), the results can be assessed and plans made for the next set of steps. BF

Keith Reid is soil fertility specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs based in Stratford. Email: keith.reid@ontario.ca