Wednesday, September 22, 2010

Assessing hail damage in mature soybeans

Significant yield loss can occur when hail events strike mature soybeans (Image 1). One such event occurred this past week in Dane County. Though the damage was relatively isolated to a few fields we measured yield losses nearing 7.5 bushels per acre. If you run into similar hail events this fall below is an equation to help you estimate the possible damage to your field. If you believe significant yield loss did occur to your field remember to call your hail adjuster before you combine.
Image 1. Shattered soybeans.

To estimate soybean yield losses from seed that has fallen on the ground:

  1. Select several random areas of the field
  2. Use a hoop or other device of known size to delineate an area and count the number of seeds in that have fallen to the ground in that area
  3. After counting the seeds that have fallen, use the following formula to calculate the yield loss:
Estimated yield loss (bu/a) = ((#of seeds on ground/average seed number per pound)/60 lbs. per bu)/((3.14 x radius x radius of hoop in ft.)/43,560 sq. ft per acre)

For example:

A 3' diameter hoop was used to determine soybean losses after a hailstorm (Image 2). An average of 220 seeds were counted inside the hoop:

((220 seeds/3000 seeds per pound)/60 lbs. per bu)/((3.14 x 1.5' x 1.5')/43,560 sq. ft per acre) = ~7.5 bushel per acre yield los

Image 2. 3' Diameter Hula Hoop

This will determine your pre-harvest losses. Any losses from the harvesting operation will be in addition to this.