From the Field-Agronomy Notes
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February 25th, 2016-
For the 2016 tobacco season, it is the Agronomy programs goal to provide up-to-date information as the crop progresses from seeding to market. We plan to report observations directly from the field as we see them or as we are made aware. Throughout the course of this new endeavor we hope to share with everyone specific recommendations that will assist with timely decision making and useful updates pertaining to the cropping situations found throughout North Carolina.
As of the last full week of February, many producers in eastern and south-central production regions of the state have finished or are quickly wrapping up much of the effort that goes into seeding greenhouses. We’ve also received a number of reports that growers in the Piedmont region are gearing up as well. The staggered effort of producers is to be expected as conditions in the east are favorable for seeding and transplanting two to four weeks ahead of those typically experienced in the Old Belt, depending on specific location.
We remind producers that it takes 50-60 days to produce a field ready transplant, with the lower range of the estimate becoming more realistic in later seeded houses. Day length is a major driver behind how quickly plants will grow as longer exposure to sunlight provides more opportunity for photosynthesis to occur within the seedlings. In addition, temperature is another critical factor for seedling growth. Greenhouse temperatures should fluctuate between 68 (nighttime) and 86 (daytime) degrees Fahrenheit during germination. This fluctuation essentially tricks the seed into “thinking” that conditions are favorable for survival. A constant temperature, no matter how warm, will not promote germination as the seed “thinks” that it is buried under the soil/media and knows that it does not have the energy reserves required to push through the soil/media profile. Now, this analogy of seeds “thinking” is a bit of a stretch but this is basic seed physiology specific to all tobacco plants. Once maximum germination occurs, typically 12-15 days after seeding, temperatures can be reduced to as low as 55 degrees without any negative effects to seedlings. The time required to reach maximum germination will vary, once again based on daylight and temperature. We recommend that seeding occur when the forecast predicts four to five consecutive days of clear, sunny days. Good sunlight penetration coupled with reasonable temperature fluctuation tell the seed that it is time grow!
Recent weather forecasts did not call for clear, sunny days….much of this was experienced yesterday (2/24) as central and eastern North Carolina experienced unseasonably harsh weather. With that being said, I might expect a slight delay in seedling emergence and instead of seeing cotyledon emergence (the first two leaves to crack the seed) at day four or five, it very well may be day six to eight before this takes place. This is not a major concern for seedling production, assuming germination is uniform across an entire house. With germination perhaps being delayed in some regions of the state, it might be in a producers best interest to add fertilizer a few days later than normal. Standard practice is to wait until seven to 10 days after seeding before adding fertilizer to the floatbed to hedge against injury from soluble salts. Waiting until 10-12 days under the referenced scenario is probably not a bad idea, but I would not wait any longer than 14 day or uneven growth could occur with older seedlings rapidly outpacing the younger ones.
There’s certainly much more to greenhouse production, so be sure to check back with us periodically. In our next post we’ll discuss cold injury (shock), how to deal with those rare dry cells, as well as any other issues that make an appearance between now and then.
As always, if you have any questions, comments, or issues, please contact your local Cooperative Extension Agent. We can also be reached through Facebook, Twitter, and Instagram, so be sure to give us a like or a follow!
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