Additional Author: Jorge Rodriguez
Episode 30 of Battle for the Belt is now available: https://www.youtube.com/watch?v=twoDYf8N9cA
In episode 30, Taylor Dill, a Ph.D. student, and Jorge Rodriguez, a visiting scholar in Dr. Laura Lindsey’s lab, demonstrate a soybean yield estimation methodology on planting dates one and five at all three Battle for the Belt locations.
Soybean Yield Estimation
Soybean yield measures four yield components; plants per acre, pods per plant, seeds per pod, and seeds per pound. There is also a printable worksheet available for yield estimates here.
The first step is to count plants per acre. We do this by counting pod-bearing plants in 1/1000th of an acre. In 7.5-inches row spacing, count all of the plants in 69 feet, 8 inches of row. For 15-inch row spacing, count 34 feet, 10 inches of row, or both rows at 17 feet, 5 inches. For 30-inch row spacing count one row at 17 feet, 5 inches.
Next is pods per plant estimation. Select 10 random plants and count all the pods on each plant that contain one or more seeds. Add up the total pod number and divide by 10 to get the average number of pods per plant.
After pod counts, we then count seeds per pod. To do this, we randomly take ten pods and count the seeds. We add up the number of seeds and divide by 10 to get the average number of seeds per pod. The number of seeds per pod is normally 2.5 but can be lower if the crop faces difficult environmental conditions.
Next is estimating the number of seeds per pound or seed size. We assume that there are 3,000 seeds per pound unless the soybean plant has faced environmental stress, then the size of the seed will be smaller (suggesting more seeds in one pound). If smaller seeds are anticipated in your field, use a seed size estimate of 3,500 seeds per pound.
Finally, we can calculate the yield estimate:
Soybean yield is difficult to predict with accuracy because of plant-to-plant variability and fall weather conditions affecting seed size. So, proceed with caution because soybean yield estimates can be inaccurate.
Battle For the Belt Location Updates and Soybean Yield Estimates
The Wooster location has corn that is still in R4. Planting date five is taking some time to mature. The decrease in temperature, moisture, and sunlight, maturation seems to have slowed down for this planting date. Planting date one in soybeans have reached R7 but the rest of the planting dates are at R6. The yield estimates for planting date one soybeans were 34 bushels per acre. Our population was 17,000 plants per acre because at this location during our first planting, the ground lay wet and cold for about three weeks (plus seedling damage was observed). Our pods per plant averaged 127.6 pods per plant and the average seeds per pod was 2.8. For planting date five, our estimation was 87 bushels per acre. The population was 104,000 plants per acre, with 47.2 pods per plant and 3.2 seeds per pod. The population effect on these two planting dates is evident, with the low population having almost three times more pods per plant on average than the higher population.
At the Western location, all the corn has reached R6 or physiological maturity. We are just waiting for the corn to dry down to harvest. Planting dates one, two, and three in soybeans all have some plots that are in R8 (95% of the plant has pods with mature color). However, only planting date one was consistently R8. Planting date four and five are both at R6 (Figure 1.) The yield estimate for planting date one is 90 bushels per acre. The population was 65,000 plants per acre, the pods per plant were 80.4, and seeds per pod were 3.1. The yield estimate for planting date five was 95 bushels per acre. The population was 79,000 plants per acre. The average number of pods per plant was 74.5, and the average number of seeds per pod was 2.9.
The Northwest corn is almost all at R6 except for a couple of planting date five plots. For soybeans, planting date one and two are at R7 (one pod at mature color) and the rest of the planting dates are at R6. The yield estimate for planting date one soybeans at this location is 119 bushels per acre. The population was 91,000 plants per acre, the average pods per plant was 75.8, and the average seeds per pod was 3.1. The planting date five yield estimation was 98 bushels per acre. The population was 106,000 plants per acre, the average pods per plant was 61.4, and the average seeds per pod was 2.7.
Figure 1. Soybeans at the Western Agriculture Research Station. Planting date one through planting date five from left to right.
Table 1. Planting dates one, two, three, four and five in the trial at all three locations with day of planting, soil, air temperature averages, and Growing Degree Days (GDDS). Information from CFAES Weather System, https://weather.cfaes.osu.edu/.
Keep following the ‘Battle for the Belt’ this growing season to learn more and get further updates! You can find the full video playlist of Battle for the Belt on the Ohio State Agronomy YouTube channel.