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Five steps to measuring field losses.
August 12, 2004

Three percent is the harvest loss gold standard. Most careful operators can keep harvest losses at 3% or less, says Duane Berglund, NDSU extension agronomist.

Heres how to measure how you are doing:. The following five simple steps can provide a good harvest loss estimate:

1 Locate three random sites in the field.

2 At each site, outline an area that is 1 ft. in the direction of equipment travel and is as wide as the effective width of the implement. For example, if a combine is picking up windrows containing 12 30-inch rows, the width of the measurement area should be 30 feet. Examine the entire width of the implement pass, not just behind the threshing section of the combine where loss can be concentrated.

3 Search the soil surface and through any soil loosened by harvest implements within the outlined area for seeds and unthreshed pods. Count all bean seeds.

4 Divide the number of seeds found by the number of square feet within the outlined area. This will provide the average number of bean seeds lost per square foot. Take an average of the three areas sampled within the field.

5 Use Table 1 to convert average number of seeds lost per square foot to pounds of seed lost per acre for specific seed sizes.

For example, if a sampled area over the full effective width of an implement pass averaged 1 pinto bean seed per square foot, the field loss would be approximately 36 lb/A, assuming 1200 seeds/lb. To extrapolate to 3 seeds/ sq. ft. for the same seed size of 1200 seeds/lb, one could multiply 3 by 1.0 by 36 lb/acre = 108 lb/acre field loss.

Short cut
Heres short cut to estimating yield. It wont be as accurate as the five steps above, but it is faster.

Take a 1 foot square frame and randomly lay it on the ground in a combined field and count the seeds inside the frame. Do this is four or five places, including sites that are not directly behind the combine. Average the count and refer to the number of pounds of seed lost. 

Use the following information to estimate the number of seeds per pound for the specific market class of the harvested bean:

      Market Class   Seeds per Pound 
        Kidney         800-1000
        Pinto         1200-1400
    Great Northern     1400-1800
    Pink/Small Red     1600-2000
      Navy/Black       2400-2800


Field loss based on the average number of seeds lost per square foot of soil and seed size of the variety harvested.

Average no. of seeds lost per square foot
 Seed Size 0.5   1.0   5.0  10.0 
 Seed/lb pounds/acre field loss
    800    27    55    272   545
   1200   18    36    182   363
   1600   14    27    136   272
   2000   11    22    109   218
   2400    9     18    91    182
   2800    8     16    78    156






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Northarvest Bean Growers Association | 50072 East Lake Seven Road | Frazee, MN 56544
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