These are the average weights for the 5 brassica green cultivars grown inside of the hoop house:

Ruby Streaks: 0.224g/plant

Mizuna: 1.112g/plant

Sue li hueng: 0.529g/plant

Surrey Arugula: 0.579g/plant

Astro Arugula: 0.464g/plant

And these are the average weights for the cultivars grown outside the hoop house:

Ruby Streaks: 0.024g/plant

Mizuna: 0.028g/plant

Sue li hueng: 0.017g/plant

Surrey Arugula: 0.027g/plant

Astro Arugula: 0.041g/plant

As you can see, the cultivar that grew most successfully inside the hoop house during the month of March was mizuna, while the most successful cultivar grown outside of the hoop house was astro arugula.

Average plant weights for each cultivar.

Based on the average weight per mizuna plant grown inside the hoop house, we can estimate the weight that could be harvest in early April if an entire hoop house were planted with mizuna in early March. Leaving a one foot row space beside each bed and a 1.375 foot border near the sliding doors, we could plant the equivalent of 990 trays of mizuna. With 100 plants per tray, and the average plant weight of 1.112g, this results in the one month hoop house production of 110 kg of mizuna! This results in a gross profit of  just over $1, 940. This is, in our opinion, an extremely low figure. In our calculations, the seeding rates are as low as the seeding rates we used in our trial. We would recommend starting the seeds in the greenhouse soil, which would allow for a much higher seeding density.

Note: Market demand is strong for out of season brassica green production. According to Jacob Slosberg, the research coordinator at UBC farm, the UBC farm could sell as much out-of-season greens as they could produce. The demand mostly comes from high-end restaurants, who are constantly on the lookout for fresh, local vegetables, which are rare at the end of March and in early April.

Calculation:

Hoop house dimension: 25 ft across x 99 ft deep

Ten 1ft row spaces across + nine 1.6667ft beds (the width of 2 trays) = 25 feet across

55 x 1.75ft tray lengths = 96.25 ft deep, leaving 1.375 feet of room by the sliding doors.

There are nine rows, each planted with the width of two trays and the length of 55 trays = equivalent of 990 trays per hoop house.

(990 trays/hoop house) x (5 rows/tray) x (20 plants/row) x (1.112g/plant) x (1kg/1,000g) = 110.088 kg/hoop house

(110.088 kg mizuna) x ($17.64/kg mizuna) = $1,941.95

Reference:

McMahen, K. (2010). Design, vegetation, and management plan for the new UBC AMS student union building rooftop garden. Retrieved from https://circle.ubc.ca/bitstream /handle/2429/34060/APBI_497_Rooftop_Garden_Final_Report.pdf?sequence=1