ISSUE 15 August 15, 2002
ESTIMATING YIELDS OF ROW CROPS
Corn Yields
There are several techniques for estimating corn grain yield prior to harvest. This version was developed by the Ag. Engineering Department at the University of Illinois and is the one most commonly used. A numerical constant for kernel weight is figured into the equation in order to calculate grain yield. Since weight per kernel will vary depending on hybrid and environment, the yield equation should only be used to estimate relative grain yield. For example, yield will be overestimated in a year with poor grain fill conditions, while it will be underestimated in a year with good grain fill conditions.
Step 1. Count the number of harvestable ears per 1/1000th acre. (Table 1)
Step 2. Count the number of kernel rows per ear on every fifth ear. Calculate the average.
Step 3. Count the number of kernels per row on each of the same ears, but do not count kernels on either the butt or tip that are less than half size. Calculate the average.
Step 4. Yield (bushels per acre) equals:
(ear #) X (avg. row #) X (kernel #)
90
Soybean Yields
Soybean yield estimates are most accurate within three weeks of maturity, but are still only estimates. Assume 2.3 bean per pod.
1. Determine the number of feet of row needed to make 1/1000 of an acre (Table 1).
2. Count the number of plants in ten (10) different randomly selected sample areas. Calculate the average.
Avg. = _______________________ = A (plants/A)
3. Count the number of pods per plant on ten (10) randomly selected sample areas. Calculate the average.
Avg. = _______________________ = B (pods/plant)
4. Calculate pods/acre by multiplying plant population by pods/plant.
A X B = _____________________ = C (pods/acre)
5. Calculate seeds/acre by multiplying pods per acre by an estimate of 2.3 seeds/pod.
2.3 X C = ____________________ = D (seeds/A)
6. Calculate pounds/acre by dividing seeds/acre by an estimate of 3000 seeds/pound.
D ÷ 3,000 = __________________ = E (lbs/A)
7. Estimate yield by dividing pounds/acre by 60 pounds/bu.
E ÷ 60 = _________________ = Yield (bu/A)
Table 1. Length of row equal to 1/1000th acre. An accurate estimate of plant population per acre can be obtained by counting the number of plants in a length of row equal to 1/1000 of an acre. Make at least three counts in separate sections of the field, calculate the average of these samples, then multiply this number by one thousand (1,000).
Row Width 
Length of Single Row 

(inches) 
(feet) 
(inches) 
6 
87 
1 
Dry Edible Bean Yields
You can estimate dry bean yields by knowing the number of seeds per pod, pods per plant and plants per 1/1000th of an acre. At the same time of counting seeds and pods, the maturity status of each should be determined.
If a seed or pod will not mature, it shouldn’t be counted. Then count the total plants per 1/1000th acre to complete the data collection.
Yield Estimation
Within a representative and uniform plant stand, randomly select five plants each from at least five randomly selected locations in the field.
Keeping all plant data separate, pull and count the pods from each plant and then count the seeds to determine average seeds per pod for all five replications. These data are combined with the average number of plants per 1/1000th acre
Average number of seeds per pound  
Kidneys 
9001000 
Seeds per pound can vary 1020% for different varieties within a bean class. If available, use reported estimates for seed number per pound for your variety.
The accuracy of yield estimate can be improved by counting seeds and pods from at least 10 plants per replication.
Calculations
Duane R. Berglund
NDSU Extension Agronomist
dberglun@ndsuext.nodak.edu
FLAX HARVESTING AND MATURITY
Flax is starting to turn in many areas of the state and the grasshoppers will be soon attacking this vulnerable crop. It should be harvested as soon as its ready to reduce crop loss and boll drop. Maturity in flax is judged by color of the bolls rather than by color of the straw. Flax may continue to bloom until frost if sown late or if the season is wet and cool. Flax is most susceptible to cold damage during flowering and early boll stages. The immature seeds, which may contain as much as 75 percent moisture, will likely be killed by freezing temperatures that do not completely kill leaves and stems. The degree of injury from freezing is dependent on the minimum temperature, condition of the plant, the soil moisture and weather conditions both before and after freezing.
Seeds from these late flowers seldom mature and are lost during threshing and cleaning. Flax is ripe enough to combine when about 90 percent of the bolls have turned brown. Any delay after this stage increases the chance of storm damage and allows weeds to grow and become more troublesome. If a swather and pickup combine are used, harvesting a few days earlier than when 90 percent of bolls are brown does not affect yield or quality.
Flax may be harvested with a swather (windrower) or by direct combining. Direct combining is the cheaper method and is entirely satisfactory when the flax is thoroughly dry and free of weeds. The use of harvest desicants can help the direct harvesting practice. However, still the most common method of harvest in many growing areas is with the swather and combine with a pickup attachment because few fields are free of weeds and few ripen uniformly. Swathed flax usually is in condition to combine after a few days of dry, sunny weather. Swath rollers are often used to pack the windrow to prevent destruction and movement by wind.
Duane R. Berglund
NDSU Extension Agronomist
dberglun@ndsuext.nodak.edu