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Think about preparing now for robust transplants in the spring.
As the 2006 season comes to an end, growers can rest, right? Well, not so fast …. Now is the perfect time to think about plant production. Experts in this article provide good advice for preparing the greenhouse for the plant-production season.
Flue-cured plant production
You may not want to think about it now, but work awaits in that shelter that’s been vacant for the last six months. “Some growers have not been to the greenhouse since they took out the last tray to be planted,” says Derek Day, county Extension director in Person County, N.C. “Old plastic used to hold the bay water needs to be removed as soon as possible. This plastic is a good home for mice, crickets, ants and other critters capable of eating an entire tray of plants in a single sitting.”
Day also advises removing weeds and grasses as they harbor insects and mice. Handle herbicides carefully in the greenhouse, he says, because some growers have injured plants in the spring by using chemicals in the fall when they cleaned up weeds and grasses. Day also suggests removing dried clippings left in the greenhouse from last season.
Two weeks before seeding, Day advises growers to take a water sample and send it off for analysis to the North Carolina Department of Agriculture & Consumer Services in Raleigh, N.C.
“Many growth problems in greenhouses could have been avoided if the greenhouse water had been tested and corrective measures taken early,” he says. “The water should be allowed to run at least 15 minutes before the sample is taken.”
In the fall of this year, check greenhouse heaters annually to avoid failures during the plant-growth stage. “Clean heaters burn more efficiently,” Day says, “and will give less trouble. No one wants a heater out when the [temperature] drops below freezing. Be sure to check all connections for gas leaks. Minute leaks can severely stunt plant growth.”
Moisture content, uniformity and a consistent mix free of sticks and clods are things to consider when choosing a quality growing medium, says Wilbur Taylor, general manager of Carolina Soil Co., in Kinston, N.C.
Cooperative Extension suggests lightly wetting the medium to decrease the amount of fill that goes through the tray holes. This may also speed up emergence.
Day advises doing an inventory on trays for any that are unusable and discarding them. “If a grower has had problems with certain plant diseases in the past, he probably will have them again this year,” he says. “Consider purchasing new trays. Be sure to fumigate all old trays to help remove some pathogens.”
Choosing the best tray often comes down to what works best for and is the most comfortable to the individual grower, suggests Chuck Miglianti, president of Beltwide Inc. in Tampa, Fla.
“We started the float system with a 200-cell tray and went all the way to a 392,” Miglianti says. “Neither is used very much any more. My guess is that a 288-cell tray is used by 75 percent of the growers. It is a good compromise of a larger, expensive 200-cell plant and the greenhouse space economies of a smaller 338 or 392-cell plant. All have worked; all have been university tested.”
He adds that after trial and error looking at cell depth and media capacity of individual cells, he found that the traditional cell capacities of the trays used in the horticultural industry were not needed.
After growers pick out the best tray for their needs, they can turn to choosing the right seed and soil. “Do not try to cut corners,” Day says. “Use good seed and soil.”
He adds that growers need to keep up with the lot numbers for each, and where each specific lot went in the greenhouse. “This will help with diagnosis if there are issues later in the season,” Day says.
Miglianti advises growers to use the mix they are comfortable with rather than changing for change’s sake. “But be aware of new technologies that might benefit you by lowering your input costs and try them on a small percentage of the crop.
“Growers should always look for medium that has been produced specifically for tobacco-float systems and not just because it says so on the bag,” he continues. “Float systems are unique in that water evaporates from the cell surface, and incorrect chemicals or ratios of chemicals in the media can gather at the media surface and can cause germination or spiral-root problems.”
The same mix in an overhead-feed system might not have these problems, Miglianti says, because the chemicals are continually flushed out of the bottom of the cell. He adds, “Moisture for wicking, wetting agents, and the right fertilizers and lime are chemical ingredients that good mix companies build correctly into mix for the float-system application for the producer.
“Particle-size distribution, water-holding capacity, air space, drain-
age—even in a float system—are physical characteristics of a mix that producers pay attention to when making a tobacco-float mix,” Miglianti says. “Costly aggregates are now less important as Canadian peat producers fine-tune their art.”
Before filling trays, “make sure the soil is all the way to the bottom of the tray,” Taylor advises. Not doing this will cause improper and non-uniform germination.
Another aspect to consider when filling trays is to focus on how the seeder drops the pellet. Taylor advises growers to make sure the pellet drops in the middle of each dibble, so they will achieve uniform seed placement.
Taylor says other things to consider when seeding include ventilating properly, and Day suggests keeping a close eye on temperature. Plants germinate better when growers seed during periods of sunny weather rather than cloudy days.
“If the extended forecast is for gloomy days, seeding should be delayed,” Day says. “The same is true for unusually cold days in the forecast. It may not be necessary to burn that extra fuel.”
Day says temperatures that are too hot are just as bad as those that are too cold. To obtain optimum germination in the greenhouse, keep temperatures between 68 degrees Fahrenheit (F) at night and 86 degrees F in the daytime. After most seedlings emerge, growers can cut back their inside temperatures from 55 degrees F to 60 degrees F at night and from 80 degrees F to 85 degrees F in the daytime.
Besides proper temperatures, Miglianti says air space and oxygen levels in the cell are important factors for good germination. “I would recommend a grower use his filler box agitator [at] the slowest rate possible that still ensures good wicking,” he says. “Packing the media results in poorer germination and poorer root growth of the plant.”
Add only the proper amount of fertilizer needed, Day advises, and monitor the salt levels in the bay water as well as the growing media. “If salts get too high in the media, be prepared to flush trays from overhead,” he says.
Finally and importantly, Day suggests that growers purchase a lock for their greenhouse door, because they really don’t know who may be visiting when they aren’t there. He says mosaic has been introduced to several houses by visitors who used tobacco products and handled plants along the walkway.
Burley plant production
Growers will do well to choose the best variety before even setting a transplant in the ground. This sets the stage for the road to not only healthy transplants but a more uniform stand. “When the producer purchases a package of seed to be placed in the trays, the course is set for that season,” says Richard Hensley, University of Tennessee research associate at the Research and Education Center in Greeneville, Tenn.
When choosing a variety, he advises growers to identify the diseases they normally deal with based on their previous field histories. They also should consider the agronomic characteristics of the varieties, such as growth habit, size and maturity group. “We are blessed with many good varieties today,” Hensley says, “but all are not good for all situations.”
After selecting the right variety, growers can evaluate their tray selection or inspect the trays they used previously. “The trays to be used in plant production need to be as close to sterile as is practical,” Hensley says.
Proper sanitized trays should have begun with the previous year’s plant season, cleaning them immediately after transplanting. When transporting trays before loading transplants, Hensley advises lining the truck bed or trailer with clean plastic, “because we tend to forget the 2-4 D we hauled or that the cow manure is a really good source of disease.”
The next step in good plant production is to choose the best media from a reputable dealer. “The media should not be from the previous year, because some of the additives tend to degrade over a period of several months,” Hensley says. “Fill the trays uniformly but do not pack the media too tightly in the cells, as this tends to make the cells hold too much water. Make sure the media goes all the way to the bottom of the cells and does not flow out the bottom before placing on the bed. If enough of the media does flow out, an air space between the surface of the water and the tray media occurs, and wicking will not occur.”
A good water source means the difference between healthy plants and very sick-looking, floppy leaves. The water source should be free of disease and chemical contaminants and kept that way, Hensley advises. Growers would be wise to avoid surface water such as streams or ponds. They also should realize that hoses and buckets used in the greenhouse can be possible contaminant sources.
Hensley suggests beginning with a minimum depth of 4 inches, maintaining this depth throughout the plant-growing season. “Be mindful that as water is added during the season, the fertility needs to be adjusted accordingly,” he says.
During transplant growth, maintaining ideal temperatures between 70 and 80 degrees F is important for good germination, Hensley says. After germination finishes, growers can lower their thermostat to 60 degrees F so they can conserve energy. Temperatures exceeding 90 degrees F for long periods of time can stop germination and slow plant growth.
“Generally speaking, if plants are smaller around the outer edges, the temperature inside the house is too cool,” Hensley says. “If plants are smaller in the center of the house, the temperatures are too warm.”
Usually, plants are ready to transplant in seven to eight weeks, so Hensley advises not to seed too early.
Proper clipping can produce uniform plants with good stem diameter, he says. Removing some of the leaf canopy allows light and air to penetrate down the stem area, which helps ward off disease organisms. Hensley advises to begin clipping when plants are about 2.5 inches tall and to remove no more than 1 inch at a time. Important: clean the mower between clippings and apply fungicides after clipping.
When applying fungicides for disease control, Hensley advises growers to spray on a seven- to 10-day schedule. “The old adage ‘an ounce of prevention is worth a pound of cure’ rings true,” he says.
Before selecting fungicides, he suggests growers contact their local Extension agents. He also warns them to read and follow label directions to avoid disaster situations that could destroy a whole greenhouse or plantbed of plants.
Another important step to effective plant production involves applying the right amount of fertilizer. Hensley advises to start slow and end slow, applying 100 parts per million of a fertilizer such as 20-10-20, which will produce enough plants in seven to eight weeks.
“Germinating seedlings do not need 100-parts-per-million nor do plants which are eight weeks of age,” Hensley says. “Start with 50-parts-per-million until approximately three weeks of age, and then increase to 100-parts-per-million. Remember that as the water level in the bed drops, the concentration of fertilizer increases. Check the water level frequently and add to maintain the desired level.”