Transplant Performance Research
Some warm season crops need to be transplanted for maximun harvest, while others can grow to maturity and produce well from either direct seeding or transplanting; other factors such as earliness and quality of harvest, cost, and equipment availability then determine if a crop is to be transplanted or seeded directly.
Optimal transplant size and seedling age, influencing costs, space, and ease of handling, need to be determined for transplanted vegetable crops.
This page contains a collection of articles detailing some of the Vegetable Program's past and current research on vegetable transplant performance. The articles are available in HTML or as PDF files.
Impact of Transplant
Age and Cell Size on Cabbage Performance PDF
Influence of Transplant
Age on Performance of Muskmelon PDF
ABA Analogs Improve Drought
Stress Tolerance of Transplants PDF
When arranging to purchase cabbage transplants, the optimum age of the seedlings at delivery and the amount of media or space each seedling is given in the greenhouse need to be determined. These factors influence both the cost of the seedling and the seedlings’ subsequent performance in the field. The longer the plants are held in the greenhouse and the greater amount of space given each plant, the larger the resulting seedling at transplanting time. The cost per seedling also increases with the time and growing space provided. Although putting the largest seedlings possible into the field might appear advantageous in terms of getting the crop off to a quick start, larger seedlings are also more prone to transplanting shock. In the 2003 and 2004 growing seasons, this study looked at the effect of age of transplants and the greenhouse space provided each seedling on the subsequent field performance of cabbage transplants.
Seedlings of a relatively slow growing cabbage cultivar (cv. Lennox) were grown in 50, 72, 128 or 288 cell trays. Greenhouse conditions and the practices used to produce the seedlings were kept as near-ideal as possible. In the 3rd week of May the seedlings were transplanted into the University of Saskatchewan Vegetable Research plots. At transplanting, one group of seedlings was 3 weeks old while the other group was 5 weeks of age. The seedlings were watered in at transplanting in an effort to minimize stress. Standard management practices were employed for the duration of the growing season. The cabbage were harvested once they reached marketable size. Time to 50% harvest, head yield and quality were evaluated.
Weather conditions at transplanting were extremely hot, windy and dry and consequently some of the seedlings were lost to transplanting stress. Transplants were also lost to rodents and birds. The remainder of the 2003 growing season was very favorable for cabbage production. The size of the seedlings at transplanting was obviously influenced by their age - the 3 week old seedlings were smaller and more compact than the 5 week plants. Seedlings coming out of the 288 cell trays were smaller and more spindly than when more space was available. Losses to transplanting stress were more severe in the older seedlings - likely because the larger older plants lost moisture more rapidly. Survival of the seedlings coming out of the 50 cell trays was superior to seedlings grown with less available space. Although the seedlings grown with plenty of space would have been larger they were also apparently more robust than the weaker plants produced in over-crowded conditions. On average, the crop grown from 3 week old transplants was ready for harvest 6 days earlier than when older transplants were used. The added stress associated with putting larger plants into the field appeared to substantially delay crop development. Cell size had an even greater impact on the rate of crop development - the crop grown from seedlings provided with the most space in the greenhouse was ready for harvest over 2 weeks earlier than the crop grown from seedlings provided with the least space in the greenhouse. Seedling age and transplant size had no impact on head quality.
The 2004 growing season was exceptionally cool and cloudy, with above normal precipitation. The size of the seedlings at transplanting was again influenced by their age - the 3 week old seedlings were smaller and more compact than the 5 week plants. Seedlings coming out of the 288 cell trays were smaller and more spindly than when more space was available. Losses to transplanting stress were not influenced by either the age of the seedlings or the size of cell the seedlings were grown in. On average, the crop grown from 5 week old transplants was ready for harvest 3 days earlier than when younger transplants were used. Cell size had a much greater impact on the rate of crop development - the crop grown from seedlings provided with the most space in the greenhouse was ready for harvest over 4 weeks earlier than the crop grown from seedlings provided with the least space in the greenhouse. Seedling age had no impact on yields. Yields obtained using the smallest size cells (288 cell) were substantially lower than the other size options. This reflects the fact that over 20% of the crop raised from the 288 cell size failed to reach marketable size prior to the final harvest in late October. Age of the seedling used had n impact on head density at harvest. However, head densities were reduced when the crop was established from the 288 cell trays.
This trial suggested that the optimum age of transplants and amount of space required by the growing seedlings varies depend on conditions during the grow out period. In 2003, heat, drought and wind stress experienced at transplanting selected against older and weaker seedlings. Under those conditions, relatively young cabbage transplants provided with abundant growing space in the greenhouse went on to produce the best stand and fastest crop development. Under the exceptionally cool conditions of 2004, better developed seedlings allowed an earlier harvest but did not provide any significant yield advantage.
Successful production of muskmelon in Saskatchewan’s short growing season hinges on the use of transplants. Transplanting allows the temperature sensitive germination process to occur under ideal conditions in the greenhouse. Transplanting also extend the effective length of the growing season. Typically cucurbits like melons are transplanted when relatively young (<2 weeks old), as they tend to become root bound and sensitive to transplanting shock. However, use of larger, more advanced transplants may be advantageous when long-season crops like melons are grown in regions with an exceptionally short growing season.
This trial evaluated the impact of transplant age on the performance of two muskmelon cultivars - Athena and Earligold. The transplants used were either 10 or 28 days old. The seedlings were planted into the field in the 3rd week of May onto IRT mulch with clear polyethylene row covers and drip irrigation. Conditions following transplanting were relatively cool and transplant survival was excellent. The cool weather however persisted for the duration of the 2004 growing season and development of the melon crop was slow. The trial was damaged by a late August frost and subsequent growth, fruit yields and fruit quality were poor.
The 28 day old transplants were substantially larger, with more leaves and better developed root systems than the younger seedlings. Because of the near-ideal conditions at transplanting, the older seedlings were not exposed to excessive transplanting shock. However, despite the developmental head start, use of older seedlings provided no yield advantage for either cultivar. As older seedlings are more costly to produce and difficult to handle these results would seem to strongly favor use of relatively young transplants for production of muskmelon. Athena performed far better than Earligold under the relatively adverse conditions experienced in 2004.
Drought and transplanting shock are common causes of loss during establishment of horticultural crops such as vegetables, ornamentals and flowering annuals. Application of abscisic acid (ABA) to young seedlings or transplants can increase their tolerance to drought stress and cold. Unfortunately, the beneficial effects of ABA applied in this way are short lived as the chemical is rapidly metabolized. PBI/NRC has generated ABA analogs which are more physiologically active and longer-lasting than standard ABA. This research program tested several ABA analogs for use in preventing drought stress in vegetable transplants.
Two week old pumpkin seedlings (cv. Jack-o-Lantern) and four week old tomato seedlings (cv. Spitfire) were treated with various concentrations of the ABA analog PBI 365 as either a root dip or as a foliar spray treatment. Following treatment, the plants were grown out under greenhouse conditions. Water was withheld from the plants and the time to wilting was recorded for the various treatments. The experiment was terminated once all plants in the stressed trial had wilted.
There were no visual indications of any acute effects of the PBI 365 dip for either crop. As indicated by Figure 1, treating pumpkin seedlings with PBI 365 as either a root dip or through foliar application significantly slowed water loss, thereby increasing the plants' tolerance to water deficits. The time to wilting was positively correlated with the concentration of PBI 365 applied. The root dip treatment was more effective at each concentration than the corresponding foliar treatment. However, given that the root dip treatment involved the application of much more of the active ingredient, foliar treatment would appear to be a promising option in terms of cost-efficiency.
The tomato plants were relatively large when treated and conditions in the greenhouse were very warm, with abundant sunlight. As a consequence, water use rates were high. Control plants wilted within two days of the cessation of watering (Figure 2) as did all the plants treated with PBI 365 via the foliar spray. Application of PBI 365 as a root dip at 10-3 and 10-4 M significantly increased the period of time prior to wilting (Figure 2).
Synthetic analogs of ABA slowed water use by transplants of tomatoes and pumpkins. This reduction in water use could protect the seedlings against the desiccation following transplanting. The extent of the protection increased with the concentration of ABA applied. Applying the ABA as a root dip was more convenient and effective than foliar application, but utilized more chemical. The ABA analogs occasionally produced some dosage dependant phytotoxicity but treatment concentrations which were both effective and safe were easily determined. Treatment with ABA analogs may also temporarily slowing the growth of seedlings - allowing handling storage or marketing at an ideal size.
Sharma, N., S.R. Abrams, and D.R. Waterer. 2006.
Abscisic Acid Analogs
Sharma, N., S.R. Abrams, and D.R. Waterer. 2005. Uptake, Movement, Activity, and Persistence of an Abscisic Acid Analog (8' Acetylene ABA Methyl Ester) in Marigold and Tomato Journal of Plant Growth Regulation. (28 July 2005: published online).
Waterer, D. 2000. Enhancing stress tolerance of high-value crops using ABA analogues. ADF Report No. 97000289 Final Report