A new app for estimating soybean yields is now available from K-State Research and Extension. KSUSoyYieldCalc is a native Android application that helps with yield estimation of soybeans before harvest following the conventional approach of counting or estimating plant populations, pods per plant, seeds per pod, and seed size. This approach was explained in detail in a previous eUpdate article: https://webapp.agron.ksu.edu/agr_social/eu_article.throck?article_id=313
The soybean yield calculator has only four inputs for predicting the final yield:
1. Plant population (plants/acre). This component can be estimated by counting the number of plants in a 21-inch row length for 30” row spacings (1/10,000th of an acre), and by multiplying that number by 10,000. For example, 10 plants in the 21-inch length of row would be the equivalent of 100,000 plants per acre.
2. Pods per plant. This factor can be obtained by counting all pods per plant in the 21-inch row length.
3. Seeds per pod. A good average number is 2.5 seeds per pod, but the range available on the app is from 1 to 4 seeds per pod.
4. Seed size. Seed size typically ranges from 2,000 (large) to 3,500 (small seeds) seeds/lb, with an average of 2,800 seeds/lb.
The last factor, seed size, is the same as the one presented in the “conventional approach.” This factor normally varies from 2,400 to 3,200 seeds/lb. If the conditions until harvest will be favorable, then the seed size component should be a lower number (e.g., 2,400 seeds/lb). If conditions are likely to be unfavorable, resulting in a short seed-fill period, then this factor should be higher (e.g., 3,200 seeds/lb). This factor will be ultimately determined as the crop approaches maturity, but an estimation is needed considering the importance of this factor for influencing final soybean yields.
Here is one example of how to use this app:
1. Plant population: 13 plants (measured at 12 sites within the field) in 21-inch row length x 10,000 = 130,000 plants/acre (measure 1 row for 30” row spacing; 2 rows for 15”; and 4 rows for 7.5” row spacing)
2. Pods per plant: 24 pods per plant, averaged over the number of plants counted
3. Seeds per pod: 2.5 seeds per pod (estimation)
4. Seed size: 3,000 (assuming “normal” conditions during seed-fill period)
Final yield estimation: 43 bu/acre
The coding for the KSUSoy YieldCalc app was developed by Tania Bandyopadhyay, Department of Computing and Information Sciences (CIS) graduate student, under the supervision of Dr. Dan Andresen, Department of CIS, in combination with Dr. Ignacio Ciampitti, Department of Agronomy. Credits: Departments of CIS and Agronomy, K-State. Downloads are free. You can download from the Google Play link:
Go to the above link or search for “soybean yield” within the Google Play website and download the application.
Ignacio Ciampitti, Crop Production and Cropping Systems Specialist