By John Thomas, Extension Educator, Box Butte County
In recent years more growers in the central high plains are moving toward direct harvest of dry edible beans instead of the conventional method of undercutting/windrowing, and then combining.
Direct harvest is accomplished by one pass with the combine. About half the time a crop desiccant herbicide is applied pre-harvest when direct harvesting beans.
Currently in the Panhandle more than 20 percent of growers are direct harvesting their dry beans. Other growing regions such as North Dakota, Michigan and Canada are using direct harvest for the majority of their dry bean harvest.
Direct harvest has several advantages: There are fewer harvest operations; beans are less vulnerable to wind and moisture because they are not placed in windrows; there is little soil disturbance, leaving more residue on the field; and less soil passes through the combine if harvested correctly.
Disadvantages to direct harvest include a later harvest date, higher potential harvest loss, need for a proper flex header, a need to learn a new system, and less availability of bean varieties as prostrate varieties are not suitable for direct harvest.
Harvest loss is often the major concern with direct harvest of dry beans. Using the conventional harvest method, an average of about 1½ bushels per acre total harvest loss can be expected in good conditions. This is based on research done in a two-year study on 24 farms by the University of Nebraska Panhandle Research and Extension Center. If conditions are poor with significant wind or rain after cutting, bean yield losses can go up significantly.
Further data gathered by the Panhandle Center indicate that direct harvest losses for pintos would average about 3 bushels per acre, and great northerns around 4 bushels per acre, if good field practices are followed. Many factors play into this harvest loss, but total harvest losses can be minimized to an acceptable level with a suitable upright bean variety, proper level field conditions, good weed control, the correct combine header, proper combine and header settings, and favorable weather.
Survey of harvest loss from grower fields
Eighteen different fields were surveyed during the fall of 2015 that were direct harvested, and harvest loss counts were taken. The range of yield losses we measured demonstrate that care must be taken when planning to direct harvest.
Total harvest loss ranged from 1.5 to 11.7 bushels per acre on the direct harvest fields sampled. The primary reasons for harvest loss exceeding 4 or 5 bushel per acre were: using non upright varieties, field surfaces that were not level, weather events that weakened plants and lowered pod height, and improper combine speed or header adjustments during harvest.
It is very important to determine harvest loss in order to make adjustments to your combine during harvest to reduce loss, or to determine what went wrong to improve your system next year. To accurately determine harvest loss you must get off the combine and do some loss counts. Two pinto or great northern beans per square foot is about a one bushel per acre harvest loss.
For an extensive guide to the direct harvest system, and more accurate means to determine harvest loss, see “Direct harvest of Dry Edible Beans”, EC309, on the University of Nebraska web site (extensionpublications.unl.edu/assets/pdf/ec309.pdf).
Direct Harvest Variety Trial
In the 2016 growing season UNL collaborated with the Kelley Bean Company in cooperation with a grower in Box Butte County to conduct a direct harvest variety trial near Alliance, with four varieties replicated four times. The beans were planted with a drill at 15-inch row spacing. Plant populations ranged from 100,000 to 120,000 plants per acre. The varieties were planted on June 7 and harvested Sept. 16 with a Case 7088 combine and a Case (by MacDon) 2162 flex draper head (30 foot). The crop was desiccated on Sept. 6.
Torreon, La Paz, Sinaloa and Monterrey varieties were compared. These are all good upright pinto varieties suitable for direct harvest. They are classified as a 2b upright indeterminate bush type bean as opposed to the type 3 prostrate plant types. See Nebraska Dry Bean Variety Trials to observe the growth types of different varieties (http://cropwatch.unl.edu/varietytest/othercrops).
The accompanying graphs show results of this trial. The top graph compares yields. These four varieties had yields ranging from 43 to 45 bushels per acre. These were good yields and would have been better if the field had not been damaged by an early August hail storm.
The bottom graph shows harvest lost. Torreon had a significantly higher harvest loss than the other three varieties at 3.6 bushels per acre. This may be due to a slightly higher yield and beans being a little dryer at harvest due to maturity.
The pod height at harvest of these varieties was not significantly different ranging from 83 to 85 percent of the pods being 2 inches or more above the soil surface. We generally like to see the pod heights above 90 percent for direct harvest, but the hail knocked the plants down somewhat. The varieties showed no significant difference in yield when analyzed statistically.
The take-home message is to choose a good-yielding variety of upright structure and do everything possible to minimize harvest loss by using farming practices suitable for the direct harvest system.