12 THINGS TO CONSIDER WHEN SELECTING A GREENHOUSE SITE: Solar Radiation & Water Supply

Selecting a “good” site for the location of a greenhouse is crucial. But what constitutes a “good” site? There are several things that should and must be considered in order to increase the
chances of a successful operation and business.
12 THINGS TO CONSIDER WHEN SELECTING A GREENHOUSE SITE:
1) Solar Radiation – Plants require sunlight in order to perform photosynthesis. When plants experience cloudy days their photosynthetic rates, and therefore their ability to grow and yield a product, such as tomatoes, cucumbers, peppers, etc., will be reduced. Therefore, a region and location with high light intensity year-round is desired.

2) Water – Water quantity and quality is crucial. Water will be needed for irrigation (maximum of 1 gal/plant/day for tomatoes). Water will be needed for the evaporative cooling system and can equal or exceed the irrigation water amounts (10,000 – 15,000 gal/acre/day). In the past, excess irrigation and bleed-off water from the evaporative cooling system was allowed to “run off” onto the ground adjacent to the greenhouse (with a rec. minimum percolation rate into the soil of 1”/hr.).
*HOWEVER, due to more strict regulations and a desire to avoid ground water contamination with high concentrations of salts, large greenhouses are now recirculating the nutrient solution.
*THEREFORE, excess nutrient solution should be recycled and/or mixed with the cooler bleed-off water and redirected onto designated areas, such as grass, shrubs, trees/windbreaks, etc.
*No matter what the source of the water, a water analysis should be done.
*Note: Sea water = 32,000 ppm (mg/l) VS Tucson water = 200-400 ppm.
Note: 640 ppm TDS (total dissolved solids) = 1 mmhos/cm or 1 mS/cm.

*Desired salt levels in the source water:
SO4 < 240 ppm_____ Cl < 140 ppm___ Non-Fertilizer Salts
Ca < 120 ppm______ Fe < 5 ppm_____ Na <50 ppm
Mg < 24 ppm_______Zn < 5 ppm_____Al < 5 ppm
K < 10 ppm________Mn < 2 ppm_____F < 1 ppm
P < 5 ppm_________B < 0.8 ppm
NO3 < 5 ppm_______Cu < 0.2 ppm
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