Jos Moerman, Sunny Bay Greenhouses
Canada: Delta greenhouse aims to be sustainable
Rainwater from the greenhouse roof is initially collected and stored in a large pond at the back of the facility. From there it is pumped to two fresh water holding tanks.
When needed, it is taken and mixed with the right amount of nutrients before it is applied, via drip irrigation, to the crop roots.
Slightly sloped gutters collect the water and fertilizer that drains out of the growing media and gravity feeds it to a storage tank. This drain water is mixed with the rainwater to get the electrolytic balance right before it is reapplied to the crop.
"The cycle is repeated endlessly with no water or nutrients leaving the system," said Moerman proudly. "Basically, it is like a large green roof system."
In addition to collecting the drain water, the gutters also help the crop to "root in." More specifically, by having the grow bags on gutters, the coco fiber growing media is warmed to air temperature and roots are stimulated to grow faster and stronger.
"A healthy root system is important," said Moerman, "because it allows the plant to produce more fruit and to better resist pests and diseases."
Healthy plants combined with the release of "good bugs" to fight insect pests have resulted in less reliance on pesticides.
"By closely monitoring the crop for pests and releasing beneficial insects and mites at the right time," said Moerman, "I haven't yet had to apply any pesticides this year."
Natural gas is burned during the day to generate carbon dioxide for the crops, which, through photosynthesis, they use to build plant tissue and fruits. The heat generated by the natural gas is stored as hot water in a large tank. Later at night, when temperatures drop, the hot water is circulated through rail pipes located close to crop roots to warm the plants.
Keeping the plants warm is complemented by a retractable screen which is computer deployed above the crop at night.
"The screen is like a giant blanket," said Moerman. "It keeps the heat from escaping and I can achieve 40 per cent in energy savings."
The screen can also be used during the day to shade the crop if there is too much sun.
The new greenhouse is six metres high, allowing the crop to grow up to five metres tall. A taller crop has many advantages.
"I can grow the crop and pick fruit for longer," said Moerman, "right until the end of November. Other growers have to stop earlier because the plant has no more space to grow."
Another advantage of tall varieties is there are more leaves at the top of the plant. This means the plant is better able to shade the fruits, thus avoiding fruit damage by sunburn.
Article supplied to the Delta Optimist by the B.C. Greenhouse Growers Association