At this time of year, we get a lot of question about estimating soybean yield. Luckily, once again, there’s an app for that and its called the MPSG Bean App. Once beans reach or surpass the full seed stage (R6 for soybeans), yields can be estimated and the MPSG Bean App will do the math for you and make it easier.
Let’s explore how this happens by working through an example:
Step 1 – Select the Soybean Yield Estimator
The above image shows the opening page of the MPSG Bean App. Select Soybean Yield Estimator from the menu.
The Soybean Yield Estimator Data Entry Page
The above image shows the top portion of the Soybean Yield Estimator data entry page. You will be working off this one page to do your yield estimate. All the data needed will be entered here. As well, there are links provided for any clarification regarding the data you need to supply to the app so that it can calculate a yield estimate.
Entering Your Plant Population
Your first task is to enter the plant population (live plants per acre) in the field you are using for a yield estimate. In the image above you can see the box where you will enter that information. If you don’t know your plant population, you are able to determine it at the time of doing your estimate and a link is provided the the Plant Stand Assessor page on the MPSG Bean App. For this example I have entered 140,000 plants per acre.
Enter the Pods per Plant
In the image above you can see the pods per plant data I have entered for this example. I have entered 10 individual counts but you can enter as many as you would like. Buttons are provided for adding additional plants or removing counts. This is data you would collect in the field at the time of doing your yield estimate. We delay doing yield estimates until R6 so that we are able to accurately count the number of pods that will be contributing to yield since flowering and new pod formation are usually done by the R6 growth stage and only pod filling continues. I would encourage you collect several pods per plant counts and to sample the whole field thoroughly. The more accurate the data entered into the app, the more accurate the yield estimate provided.
Estimate Seeds Per Pod and Seed Size
In the image above you can see the sliding scale buttons that are used to estimate the seeds per pod and the seed size of the harvested crop. This the point where the accuracy of the yield estimator can really suffer as these are data points are harder to determine for the field you are assessing.
The long term average across the Manitoba soybean crop over the years has been 2.3 seeds per pod and so the sliding scale defaults to that number. If the growing season is stressful you would want to reduce the number to about 2.0. Or, if the growing season has been particularly stress free, you might want to increase the seeds per pod number. If you want to be as accurate as possible, I would encourage you to do actual counts. You have already pulled plants to determine pods per plant so use those samples to collect data for your average seeds per pod number. Again, the more data that you use to determine your average seeds per pod, the better!
For seed size, we recommend entering the seed size according to the variety you have grown (found on the seed tag label). If you expect larger seeds due to good growing conditions decrease the value to 2400 seeds/lb (larger seed). If you expect smaller seeds due to poor growing conditions, increase the value to 3200 seeds/lb (smaller seed).
In my example above, I have set the seeds per pod to 2.3 and my seed size to 3000 seeds/lb.
The Big Moment – Estimate Soybean Yield!!
As per the image above, now that all the data has been entered for my example, I tap the Estimate Soybean Yield button and I get the happy news of 41.5 bu/ac. But, before I run off and put a down payment on that new combine, I need to exercise some caution around the yield estimate.
Yield estimates are only as good as the number of counts taken. Yields are highly variable within fields, so increasing the number of counts and taking counts from different areas can improve the accuracy of estimates.
Further, I would treat, even the most well done yield estimate, as only a guideline that, at best, can tell you if you are looking at a very poor, average or very above average crop. Technologically we are not at the stage yet where commercially available highly accurate whole field yield estimates are possible. I definitely wouldn’t head to the bank or dealership until after harvest is done!!
The MPSG Bean App features six unique, interactive tools to assist soybean and dry bean farmers with important crop production decisions.