Use of north wall of a greenhouse for nursery raising

An existing greenhouse was modified for nursery raising on the north wall using optimized stacks along with regular crop raising on the greenhouse floor. Nursery trays were optimally designed and mounted in two stacks on the north wall in such a way that at solar noon no fraction of solar radiation leaves through it and also does not cast any shadow of the upper stack onto the lower stack and on the plants grown on the floor. It was computed that from November to February, the optimum ratio between the height of two consecutive stacks (H) and width of the tray (W) is 1.07. Two nursery raising cycles of tomato seedlings were successfully completed from 15^th Nov 2009 to 5^th Jan 2010. About 4500 nursery plants per stack (three trays) were produced in one cycle. Hence, during the four winter months of November, December, January and February in Punjab climate, the small greenhouse of 600 cm × 400 cm size having 600 cm long and 210 cm high north wall can be used commercially to produce more than 20000 nursery plants by completing five cycles. By selling four plants for one rupee (current market rate for tomato crop), significant extra revenue (Rs 5,000) can be generated in addition to the returns obtained from the matured crop.