Presentation of yield data revisited (article from HortScience 30(3): 420, 1995).
I was interested to read the letter by John D. Downes in HortScience 29(6):606 encouraging authors to present yield in standard units. I have studied yield trialing techniques (HortScience 22(6):1220-1223) and concur with his statements. Timothy K. Hartz is correct in his reply that plot yields may be inflated relative to what is expected for growers. However, it does not help the situation to present the data as kilograms per plot because the yields are still inflated and the units presented are more difficult for the reader to interpret. (Plot sizes used in experiments are quite diverse, depending on the research goals and resources available.)
The best way to present yield data is to use standard units (megagrams per hectare) so that growers and scientists can compare published experiments easily and then remind the growers about factors that reduce yields when translating from the experimental situation to the grower’s field. We get 33.8 Mg/ha in our trials with cucumbers (Cucumis sativus L.), but growers get only 9.8 Mg/ha. However, if oversized and cull fruit and plot end effects are removed and data are corrected for the addition of 15% monoecious pollenizer to the gynoecious hybrid cultivar (asuming the pollenizer has approximately 70% the yield of ‘Calypso’), then we would get 19.8 Mg/ha. Thus, good growers should expect to get 19.8 Mg/ha from ‘Calypso’ in the spring season in North Carolina using the recommended cultural practices (in fact, they do). My calculation of those factors in the case of pickling cucumber are in Table 1.
Todd C. Wehner
Department of Horticultural Science, Box 7609
College of Agriculture and Life Sciences
North Carolina State University
Raleigh, NC 27695-7609
Table 1. Estimated yield of pickling cucumber for the average North Carolina grower.
|Yield of ‘Calypso’ pickling cucumbers in North Carolina
Maximum in North Carolina State Univ. trials, spring season (1978-93)
Mean in trials, NCSU spring season (1978-93)
End effect (1.5-m alley separating 6-m-long plots), -15%
Oversized fruit (>51 mm in diameter not marketable), -15%
Cull fruit (crookeds and nubbins not marketable), -15%
Add 15% pollenizer to gynoecious hybrid, -10%: corrected yield
Mean yield for North Carolina growers (county agent estimate, 1978-93)