Estimating Soybean Yield

This is the time of year when many are wondering what kind of yield potential is out there.  You can estimate your yield using the steps outlined below.  But I will warn you that such an estimate is not very accurate until soybean reach the late-R6 or R7 stage.  In my experience, when trying to estimate yields during the late-R5 or early-R6 stages, cut the estimate in half – believe it or not, that usually works!

My point is to use extreme caution.  Never make additional sales based on these “estimates”.  But, such an estimate is useful if you’re thinking about entering a yield contest or just to help ease some worries (or maybe cause more).

To estimate soybean yield:

  1. Calculate the number of pod-bearing plants per acre.  Use the 1/100th of an acre method: Count the number of plants per 70 foot of row (7.5-inch spacing), 35 foot per row (15-inch spacing), or 17.5 foot per row (30-inch spacing) – You can adjust this for other row spacings; then multiply by 1000.  Do this in 5 to 10 locations per field, depending on field size or area of interest.
  2. Estimate the number of pods per plant.  Some say to collect 10 random plants.  I don’t particularly like this method because we tend to select the best plants and overlook the weaker ones with few pods.  I suggest taking 10 plants in a row from the same locations you sampled for plant population.  Divide the number by 10 to get pods per plant.
  3. Estimate the number of seed per pod.  This gets a little more difficult.  You can choose a number from visually observations or you can just use 2, 2.5, or 3 seed per pod to get a range.  If the seed are mature, you can shell and count all pods from several plants at each  sampling location (just remember how many pods you shelled).
  4. Estimate the number of seed per pound.  3,000 seed per pound is about average, but it can range from 3,500 to 2,500 per pound.  Also, be careful with varieties that commonly contain 3 seed pods; the seed of these varieties will almost always be smaller.  Another way to do this is to weigh the seed that you shelled from step 3 – be careful, you need to account for seed moisture and if the seed are not yet mature, they may have not stopped filling.

Use the numbers above to calculate yield using the equation below:

Bushels per Acre  = [(plants/1,000th acre) x (pods/plant) x (seeds/pod)] ÷ (seeds/pound) ÷ (60 pounds/bushel)

The easiest mistake to make is in steps 3 and 4.  I suggest using a range of seed per pod and seeds/pound.  With experience, you’ll get pretty good with yield estimates.