Approximately 10,000 acres of Vidalia onions are grown each year in Georgia with a farm gate value of $168 million, making the crop very important for the state’s economy (Center for Agribusiness and Economic Development, 2022). Despite the large area and value, Vidalia onion production requires a significant amount of manual labor since transplanting and harvesting are performed primarily by hand. With hand labor being performed simultaneously by several field workers, there could be some inconsistencies among them. These inconsistencies could be related to how deep the seedlings are getting transplanted, which could lead to poor root-to-soil contact and potential yield decrease.
Experimental Treatment
To measure the impact of possible hand transplanting inconsistencies, an experiment was conducted at the UGA Vidalia Onion and Vegetable Research Center in Lyons, GA. The treatments were designed to replicate previously seen field situations. A 10-ft bed was hand transplanted simulating onions well transplanted, partially transplanted, lying on the ground, and multiple transplanted. A list of treatments is shown below, and Figure 1 shows the visual examples of inconsistencies in seedling transplanting.
- Treatment 1: 25% of seedlings lying on the ground.
- Treatment 2: 25% of seedlings partially transplanted.
- Treatment 3: Control (100% of seedlings properly transplanted).
- Treatment 4: 25% of multiple transplanted seedlings. Multiple transplanted seedlings represent two or more seedlings transplanted in the same furrow.
- Treatment 5: 100% of seedlings lying on the ground (to measure mortality).
Results
Plant growth was measured by the number of leaves per plant, and plant mortality was determined by the bulb population.
The best results for leaf number were observed in Treatment 3 with an average of 7.33 leaves per plant, statistically differing from all the other treatments (Figure 2). Treatments 1, 2, and 4 showed no statistical difference among them, although the lowest number of leaves among them was presented by T1 (5.98).
All treatments differed from Treatment 5, which had the lowest number of leaves, with an average of 4.6 leaves per plant.
The highest population was observed in T4 (Figure 3) as expected (144.75), since this treatment received more than one seedling in 25% of the furrows. T3 (properly transplanted seedlings) showed a final count of 113 plants (right on the target population). T1 (25% lying on the ground) and T5 (100% laying on the ground) had populations of around 95 plants, representing a 16% mortality rate when compared to the control treatment.
The observed results in the treatments with seedlings lying on the ground was expected, as seedlings with exposed roots are sensitive to abiotic factors. These factors include water loss to the atmosphere because of sun exposure, difficulty in obtaining water and nutrients from the soil during the post-transplant period, and an increased likelihood of insect attacks and fungal and bacterial diseases.
The yield from each treatment is shown on Table 1. As expected, the higher yield was found where the most onion seedlings were transplanted, at the 25% multiples treatment. The second highest yield was observed at the properly transplanted treatment. The two lowest yields were observed at the treatments where seedlings were left on the ground. There was a significant difference of about 10,000 lb when comparing properly transplanted seedlings to the 25% lying on the ground treatment and about 4,000 lb when comparing properly transplanted seedlings with seedlings that were partially transplanted.
| Treatment | Yield, lb/acre |
|---|---|
| 25% lying on ground | 28,115 b |
| 25% partially transplanted | 44,104.5 ab |
| Properly transplanted | 48,460.5 a |
| 25% multiples | 51,183 a |
| 100% lying on the ground | 15,790.5 c |
| Means followed by the same letter within a column are not significantly different according to the Scott-Knott test at a 5% probability level. | |
Figure 4 shows the size grading for each treatment. Results show that the higher percentage of jumbo Vidalia onions was found when the seedlings were properly transplanted all the time (88.4%). The results also show that even though there was a higher population found at the treatment with 25% multiple seedings transplanted, the percentage of jumbo onions was lower.
There was a high concentration of medium onions at the 100% lying on the ground treatment, which shows that even though the population was lower, the plants didn’t have enough vigor to swell the bulbs. This also could correlate to the lack of leaves.
During the grading operation, we also found that there were several onion bulbs smaller than a medium, which passed through the grading machine (the grading machine used only grades medium, jumbo, and colossal). Figure 5 shows that on the treatments where seedlings were left lying on the ground, the bulb swelling was lower, resulting in smaller bulbs (1 to 2¼ in.); 24.6% of the medium bulbs were considered small on the 100% lying on the ground treatment, and 11.8% on the 25% lying on the ground treatment.
Conclusion
Properly transplanted seedlings showed the best growth and yield, with the highest leaf count and bulb population. Treatments simulating poor transplanting conditions (e.g., seedlings lying on the ground) showed reduced growth, higher mortality rates, and lower yields. The yield difference between properly transplanted seedlings and those lying on the ground was significant, underscoring the importance of transplanting quality. Properly transplanted seedlings also showed the most uniformity on onion size.
If you need any information about this article, please contact Luan Oliveira at 229-386-3377 or luan@uga.edu or Chris Tyson at 912-565-7822 or tysonc@uga.edu.
Reference
Center for Agribusiness and Economic Development. (2022). Georgia farm gate value report 2021 (Report No. AR-22-01). University of Georgia College of Agricultural and Environmental Sciences. https://caed.uga.edu/content/dam/caes-subsite/caed/publications/annual-reports-farm-gate-value-reports/2021_GeorgiaFGVReportDec2022%20(1).pdf
