Handy harvest info.
September 01, 2003
How to read tailing returns, estimate harvest losses and get the most out a desiccant
If you have grown dry beans for a while, you probably have forgotten more things than anyone can tell you about harvesting dry beans.
Here is some information that is always handy to have around at harvest.
What tailing returns tell you
Any appreciable quantity of threshed beans in the tailing return indicates that the adjustable chaffer is set too tight. Completely threshed beans returning through the auger for rethreshing will increase the amount of split beans and checked seedcoats.
Check the grain tank for dirt and foreign material and for beans that are split or have checked seedcoats. Excess dirt and chaff generally indicate that the adjustable sieve is adjusted too wide or that the fan blast is inadequate or improperly directed.
Excessive checks and splits generally indicate one or more of the following:
* The cylinder speed is too high.
* The cylinder concave clearance is too small.
* Too many concave bars or grates are being used.
* Too many completely threshed beans are being returned through the tailings system.
How to measure harvest losses
Five simple steps can provide a good harvest loss estimate:
Locate three random sites in the field
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.
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.
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.
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.
Table 1. 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
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
Great Northern 1400-1800
Pink/Small Red 1600-2000
There are two products currently labeled for desiccation of dry beans - Gramoxone Max (paraquat) and Drexel Defol (sodium chlorate).
Tips on using the two desiccants include:
Gramoxone Max Rate: 0.75 to 1.3 pt (0.28 to 0.49) per acre. Apply seven or more days prior to harvest. Apply when at least 80% of the pods are yellow and mostly ripe with no more than 40% (bush type beans) or 30% (vine type) of the leaves still green.
Drexel Defol Rate: 1 gal of a 6 lb/gal concentrate per acre. Apply 7 to 10 days prior to harvest and after pods are brown. Thorough coverage of foliage is essential. Apply in 5 to 10 gallons per acre by air or 20 to 30 gallons per acre by ground.
Gramoxone Max is a contact herbicide and is dependent on light and temperature for maximum control, says Richard Zollinger, NDSU extension weed specialist. "Application under full sunlight and hot temps allow the product to work best. Because the application is done later in the summer or fall, temps are cooler during this time and that is why some growers may have had less than ideal performance with this product. Also, being a contact herbicide, coverage is important because only plant tissue intercepting spray will be affected. Use sufficiently high spray gallonage to cover not only leaves but vines. Rain prevents desiccation and cancel the action of paraquat."
For more information, visit www.northarvestbean.org, and follow links to the crop production guide and the harvest section.