Del Voight - Penn State Extension - Crop Management
I have recieved a few calls on estimating soybean yield to determine which areas to select for the Soybean Yield Contest. I can relate that this is very difficult to estimate accurately. To come up with some idea of yield here is a simple procedure to follow to determine yield.
Determine plant population
Reference row needed to equal 1/1000th acre. I use this primarily since it is difficult to walk beans at later stages of growth.
(inches) Length of Row Needed to Equal 1/1000th Acre
6 87 feet 1 inch
7 74 feet 8 inches
7.5 69 feet 8 inches
15 34 feet 10 inches
30 17 feet 5 inches
Determine the Pods Per Plant
This will vary with weather. Be sure to count the pods on the branches as well. Do this for at least 10 plants to get more accuracy.
Determine Seeds Per Pod
Typically you will find 2.5 seeds per pod. In ideal weather 3 and 4 beans might be noted. In dry conditions this can drop to 1-2. Get a handle by counting a few and averaging what you think is the average seeds per pod.
Determine Seeds Per Pound. This is difficult. Beans vary in wieght dramatically from 2000-3600 beans per pound. The average is about 2500 and this is what I typically would use. If a drought year exists during pod fill then higher seeds per pound will exist.
Enter Information into a calculation to determine estimated yield
the following yield estimate is determined:
(plants per acre) x (pods per plant) x (seeds per pod) ÷ (seeds per
pound) ÷ (pound per bushel) = (bushels per acre)
121,968 x 22 x 2.5 ÷ 2,500 ÷ 60 = 44.72 or 45 bushels per acre
Keep in mind that accuracy is difficult. Harvest loss and other deviations can make the estimate way out of line.
Here is a sheet that may assist you in recording field information.