winter lettuce production
“local growers who can provide a steady supply of
fresh, gourmet-quality lettuce can often charge premium
prices or above, while saving money on shipping costs.”
Lettuce is a great crop
for year-round greenhouse production,
particularly in northern latitudes. Lettuce
is a low-light, lowtemperature crop,
so supplemental
lighting and heating
costs can be kept to a
minimum. Lettuce is
also a perishable crop,
giving local growers who
pick fresh and deliver daily
a competitive advantage.
For example, shipping lettuce from the West Coast to the
East Coast in temperature-controlled containers may cost
as much as 40 cents per pound, and the longer the lettuce
is in transit, the more that may be lost as scrap. On the
other hand, local growers who can provide a steady supply
of fresh, gourmet-quality lettuce can often charge premium
prices or above, while saving money on shipping costs.
What to Grow
Head lettuces, such as iceberg lettuce, are not usually
recommended for hydroponics, but there are many leaf
lettuces and other leafy vegetables that are well-suited for
hydroponic applications. Bibb lettuces are the most popular,
with fast turnaround times and excellent quality. Romaine
lettuce takes a little longer to grow, but can command
higher prices, especially in years when field production is
poor. Spinach is great for hydroponics since there is no
sandy grit, and other green vegetables such as bok choy and
arugula can be grown for specialty markets. Another emerging market is microgreens. Microgreens are baby lettuces,
mustards and herbs that are densely sown and harvested
in days, and they often bring in premium prices in niche
markets. Whether growing for home use or for commercial
production, a wide variety of lettuces and leafy vegetables
can be successfully grown in hydroponic systems.
The System
By far the most popular hydroponic system for lettuce production in the United States and Europe is the nutrient
film technique (NFT) system. The lettuce is placed in plastic gullies, usually between 2.5- and 6-in. wide, and a thin
film of nutrient solution trickles over the bare roots. The
nutrient solution is stored in a reservoir, and a submersible pump pumps the solution to the far end of the gullies.
The gullies are placed at a slight slope so the nutrient
solution flows down the gullies to be collected at the other
end and returned to the reservoir. The system then recirculates the nutrient solution over and over again. Since
the nutrient solution is flowing in a thin film, aeration at
the root zone is optimal, and since the reservoir is in a
closed system, it is possible to capture, clean and reuse the
nutrient solution for maximum efficiency. Only a fraction
of the water and nutrients required for field production is
necessary, and there is little or no runoff of concentrated
fertilizer salts to pollute the environment.
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Maximum Yield USA | January 2015