Tag: High tunnels

Improving research in controlled environment facilities

University researchers, extension specialists, industry
representatives and USDA officials are working together to improve how research
is conducted in controlled environment structures, including greenhouses.

By David Kuack
North Central Extension & Research Activity–101
(NCERA-101) is a committee of the USDA
organized to help plant scientists understand how to use controlled environment
technology. The committee initially began in 1969 when plant scientists in the
American Society for Horticultural Science began to discuss how to effectively
use growth chambers to ensure consistent and comparable growth data. When the
committee was organized in 1976 as the North Central Research-101 (NCR-101)
committee, the group expanded to include all plant science researchers and
began encouraging private industry groups to participate.

NCERA-101 was organized to help plant scientists understand
how to use controlled environment technology.
Photo courtesy of University of Alaska

NCERA-101 now has
over 160 members from 102 institutions and industries. There are even members
from outside the United States.

“NCERA-101 is a project with USDA,” said University of
Alaska horticulture professor Meriam Karlsson, who is the chairperson of the
committee. “USDA has several of these working groups or committees that work on
special topics. This committee is particularly large compared to some of the
others because of the involvement of industry members along with researchers.”
Poster child for
cooperation

Karlsson said the NCERA committee has to apply for
renewal every five years to keep operating and to keep receiving funding from
USDA. The USDA funding is distributed to land grant universities and their
experiment stations.

“The committee is open to industry and non-university
persons working with controlled environment technology appropriate for plant
research and production,” said Karlsson. “That is part of the reason the
committee has become so large. Industry members provide input and support the
work the university and extension personnel are doing. We can also communicate directly
to the industry members what kind of technology is needed in both greenhouses
and growth chambers in order to control the environment.”
Karlsson said USDA officials are very happy with the way
NCERA-101
has been operating with the communication and cooperation that is occurring
between university scientists and industry members.
“USDA officials tell us this is how they would like other
committees to work together on multi-state projects,” she said. “USDA works
with a sizable list of working groups,
including animal sciences, forage, insects and diseases. There is no limit in
regards to the number of members the committee can have, although to keep
focused the group needs to remain manageable. NCERA-101 also collaborates with
similar working groups in Europe and Australia. In two years the meeting will
be international and held in Australia.”
Information sharing

As chairperson, Karlsson prepares an annual report and
the committee holds an annual meeting, which occurred in Alaska earlier this
year.

“During the meeting there is information sharing among
the members,” she said. “Everybody is asked to give station reports and talk
about what they are working on. It primarily has to do with how the researchers
are using controlled environment technology. It could be greenhouses, but much
of the research is being done in growth chambers, phytotrons and biotrons. The
discussions are very specific about how to run the growth chambers and what
kind of variables to measure.”
Karlsson said one of the hot topics of discussion among
the members is lighting and LEDs.
“Right now it’s very confusing as to how to evaluate LEDs,”
she said. “This is one of the committee’s areas of focus—light measurement, how
to provide sufficient light and how to use light. When using artificial lamps
there isn’t a natural spectrum.”
Another topic of discussion has been about humidity and
its effect on plants.
“How do you measure humidity and provide it
consistently?” Karlsson said. “Much of the discussion is related to how to
characterize the environment. The same types of discussions also occur
regarding the instrumentation that is used to measure these variables. The
committee works on developing guidelines for measuring these essential
variables.”
The guidelines developed by the committee can then be
used by scientists worldwide to consistently measure environmental conditions
regardless of where the research is conducted.
“Industry members also discuss the challenges they face
in regards to developing the measuring instrumentation that the scientists are
telling them is needed,” she said. “The scientists want the equipment to
measure a variable with limited influence of other factors.”
New greenhouse
open house

During this year’s NCERA-101 annual meeting, which was hosted
by the University of Alaska Fairbanks, Karlsson had the opportunity to show off
the new teaching and research greenhouse that was recently completed. The
4,500-square-foot Nexus greenhouse consists of an upper and lower level. The
upper level, which was completed in 2012, is used for teaching and
instructional purposes. The lower level, which was finished earlier this year, will
be used for research.

 The new greenhouses at the University of Alaska
are equipped with high pressure sodium lamps.
Photo courtesy of University of Alaska 
The greenhouses are equipped with both blackout and
shade/energy curtains. There is also a Mee fog system which is used to cool the
greenhouses and to increase the humidity.
“During the winter the natural humidity is really low,”
Karlsson said. “During the summer when the temperatures can reach into the 80s,
the fog system keeps the greenhouses cool.”
Karlsson said when the greenhouses were being planned
during 2010-2011 the decision was made to install high pressure sodium lamps.
“At the time the technology for the LEDs was not
developed enough for us to choose them,” she said. “We are doing research with
LEDs because the cost of electricity here is very expensive and LEDs are anticipated
to be more efficient. I expect LEDs will make a big difference for the
commercial greenhouse industry in the state. We are looking at how we can get
enough light from LEDs to substitute for high pressure sodium to promote the
kind of growth we want to have. And we need to determine how plants respond to
different light qualities under our growing conditions.”
Interest in food
crops

Karlsson said there is a lot of interest in many
communities in Alaska about hydroponics and the production of food crops.

University of Alaska researchers are studying the
feasibility of growing a variety of edible crops.

“Alaska is at the end of the supply line so there is a
lot of interest in extending the growing season and even possibly growing
during the winter months,” she said. “We are looking at growing hydroponically and what is the
easiest way to produce leafy greens, lettuce, tomatoes and cucumbers. Even
though Alaska is known for having major natural gas and oil reserves, having an
affordable energy source is one of the obstacles that has to be addressed. Some
communities have access to natural gas, which is almost an unlimited resource.”

Karlsson said because of Alaska’s cold, dark winters,
there is interest in growing hydroponically with vertical shelf systems.
“There is also a lot of interest in greenhouses and high
tunnels,” she said. “Alaska is a big state. South of Anchorage on the Kenai
peninsula, high tunnels are used to start the season earlier in the spring and
to extend fall production. The climate is more moderate there. As you go
further north, it doesn’t make sense to put up a high tunnel. Greenhouses would
be a better choice. Even during the summer when there is plenty of light, some
heat would be needed in the greenhouses to maintain the warmer temperatures the
crops would need.”

For more:
Meriam Karlsson, University of Alaska Fairbanks, (907) 474-7005;
mgkarlsson@alaska.edu.

David Kuack is a freelance technical writer in Fort Worth, Texas; dkuack@gmail.com.

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Hort Americas new Supplemental and Artificial Lighting Education Video

Hort Americas just released its newest video designed to help people interested in using supplemental or artificial lighting in hydroponic, vertical farming, urban ag, tissue culture and greenhouse applications.

Whether you are looking to purchase high pressure sodium lamps, need photo-periodic lighting, learn more about LED Grow Lights or simply have any other lighting questions…this video series will help.


Understanding Light Quantity and Its Effect on Commercial Horticulture from C Higgins on Vimeo.

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Consider edible greens as an alternative crop

Growers of ornamental plants can use empty greenhouses during winter to produce a variety of edible greens.

By Tina Smith

Ornamental plant growers who close down their greenhouses for the winter may consider using an empty house to produce an alternative crop such as greens during the winter months. Production systems range from high tech hydroponic systems for lettuce to growing mixed greens in ground beds using minimal or no heat. Researchers in the Department of Plant Science at the State University of New York (SUNY)–Cobleskill, are using existing ebb and flow benching for short-term hydroponic raft lettuce production.
One thing that is common to most greens production systems is the use of a greenhouse structure. Since many greenhouses used to grow spring ornamentals are vacant between November and February, greens may be an alternative crop.

Start small
When growing a crop of greens for the first time, especially if new to vegetable production, begin on a small scale. Growers are advised to research the markets including demands for certain types of greens, harvesting techniques, post harvest handling, storage and packaging. Areas with winter farmers markets have seen a high demand for winter greens, though in some cases the market is getting saturated and competition is high.
Resources are available on growing greens in high tunnels that can be adapted to greenhouse production. It may take some trialing to develop a production system that works for your operation.


Greens being grown in ground beds.

Minimum heat production
Greenhouse growers who produce ornamental crops tend to grow greens in soilless mixes or compost in containers on benches. For production systems that use minimal heat, greens are sown from early September through the first week of October and harvested in November and December.

Scheduling
Planting times are one of the most critical factors for winter harvesting of greens. Successful growers develop planting schedules including expected harvest dates and record yields for future use.
Early sowing is necessary because greens achieve most of their growth before short days lengths and cold temperatures occur. The growth rate slows during the winter months due to cold temperatures and low light caused by cloudy weather and shorter day lengths. There is very little or no growth when the day length drops below 10 hours per day, which usually occurs at the end of November through the beginning of February in Massachusetts. If minimum heat is used, winter production of greens relies on the plants making their growth throughout the fall. Recent research at the University of New Hampshire suggests that some species are more sensitive to temperature than to light whereas others such as lettuce are more sensitive to light than to temperature.
One of the keys to success is to plant enough of a crop early in the season to be able to harvest through the cold season. For example, spinach may take several months to grow during colder months. Spinach seed should be sown in September and October so it is nearly full-sized in December and can be harvested through February.


Greens being grown in flats.

Types of greens
There are several types of greens that are grown for winter production, including Asian greens such as mizuna and tasoi, kale, lettuce (red and green leaf, oakleaf and romaine), mustards, gourmet cabbages, Swiss chard, spinach, arugula and claytonia.
If you unfamiliar with some of these greens, taste them first and check out recipes for greens that are new to you. This can help with the best way to market the different greens.
Lettuces are not as cold hardy as some other greens and some lettuce varieties are better adapted to cold weather and short days. Seed catalogs can help with specific growing requirements.
Spinach is very cold hardy. However, during the darkest period of winter, spinach grows very slowly. As the day length becomes longer spinach regrows rapidly and some varieties bolt before the end of winter (February or later).
Crucifers, including mustards, raab and Oriental greens such as pak choi and tatsoi, are good choices for cold-weather production. Swiss chard (Beta vulgaris), which is grown for its large tender leaves and rapid re-growth, is cold hardy and productive.
Growers have found it best to plant different varieties in separate production blocks rather than mixed them together, since growth rates and times of maturity are different. Trial several varieties because they may grow better under various light and temperature regimes. Some varieties are quicker to bolt than others. Mixed packages of greens can be created after they are harvested.

Cultural methods
Containers. Greens can be directly sown in a variety of containers. Open seed flats are popular and fit well on benches. Some growers cover the benches with landscape fabric and fill with medium to create one large bed.

Growing media and fertilization. Soilless media or composts are used for growing greens. Organic production requires growing media that have been approved by an organic certifying agent or have been designated OMRI certified. Plants need less fertilizer as the growth rate slows. Avoid over-fertilizing, which can lead to soft growth and aphid infestations.

Irrigation. Automatic sprinklers or hand watering can be used. Irrigate plants in the morning to allow foliage time to dry before temperatures drop at night, especially as the day length shortens. Under short days growth slows and less water is used. Avoid overwatering, which results in soft growth. Soft plants are less able to withstand cold and have less flavor.



Greens being grown on subirrigation benches.

Temperature. There are many options when it comes to temperature. Temperature affects the growth rate and also the flavor of greens. For example, arugula has a stronger flavor when grown at warm temperatures. Some growers produce a succession of greens harvesting every 14-21 days (micro-greens) at 50°F nights and 55°F days. Other growers provide minimal heat to maintain night temperatures of 37°F. On warm or sunny days, greenhouses are ventilated or the side walls are rolled up to increase air circulation depending on the structure.
Some growers use ground beds without supplemental heat. Some crops such as lettuce and arugula do not grow well without supplemental heat. Growers who are using high tunnels without heat tend to use row covers laid over crops on cold nights. The covers must be removed during the day to allow the plants to receive light. Greens cannot be harvested frozen and must be thawed before harvesting.

Light. Light affects the growth and flavor of greens. Decreased daylight results in slower growth. Increasing the temperature cannot compensate for the reduction in daylight. Greens tend to have a milder flavor under lower light. Mesclun grown under lower light is lighter colored than when grown under high light conditions.

Pests. Some of the pests that may be encountered when growing greens include downy mildew on lettuce and spinach (two different species of downy mildew). Some newer varieties of spinach are promoted as having resistance to many races of downy mildew. However, this resistance may not be for all races of the disease. Powdery mildew is a problem on lettuce under low light and high humidity conditions. Voles can be also be a problem when growing greens.

Harvesting and marketing. Greens can be harvested using a sharp knife, scissors or manually picked with no tools, one leaf at a time. Growers use both short and long blade knives. Greens can be harvested by either removing outer, larger leaves at regular intervals or by cutting the entire plant within an inch above the growing medium allowing the crown to remain. Leafy crops re-grow and can be harvested again.
Once greens are harvested, some growers move the crop to a storage area to bag them for sale. If the greens are dirty, then they need to be double rinsed and spun to remove excess moisture. Spinach tends to grow close to the ground and may need washing. Growing in a soilless medium or compost in containers on benches can eliminate this step.
Two popular markets for greens are winter farmers markets and restaurants. Many community-supported agriculture (CSA) farms are offering winter shares and some may be interested in buying in greens to add to the winter and storage crops they offer.
Tina Smith is with the UMass Extension Greenhouse Crops and Floriculture Program, (413) 545-5306; tsmith@umext.umass.edu.
This article first appeared in the July-August 2012 issue of the UMass Extension Floral Notes Newsletter.

References and Resources
1. Summer Flowers, Winter Greens; http://www.growingmagazine.com/print-7190.aspx
2. Four Season Farm: “Growing Winter Crops in Maine” and “The Winter Harvest Handbook”; http://www.fourseasonfarm.com/books/index.html
3. Cornell High Tunnels website: Cold Hardy Greens; http://www.hort.cornell.edu/hightunnel/crops/vegetables/salad_greens.htm
4. Michigan State University Hoop House website; http://hoophouse.msu.edu

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