Cropping in Arid Area Greenhouse

In hot, arid regions, yields are low and unstable, growing season limited to one. Greenhouses can stabilize and improve yields and extend seasons. But their adoption is impeded by the requirement of large amount of water for (evaporative) cooling. Arid Area Greenhouse (AAG) is being developed to reduce or eliminate this need by employing earth-tube-heat-exchanger (ETHE). A prototype AAG was installed in the year 2002 at village Kothara (ϕ 23° 14 N, λ 68° 45 E, at 21 m a.s.l.). AAG is of 20 X 6 X 3.5 m size. ETHE is buried 3m deep and coupled to AAG in closed-loop. ETHE provides 20 air changes per hour. There is provision of closable vents - two along the base of long sides and one along the ridge. A retractable shading curtain is provided over the roof. By now five rounds of cropping have been done. ETHE was able to heat the greenhouse from 9° C to 22-23° C in half hour in the cold winter nights. Static ventilation along with shading was effective for day time control till early March. Subsequently ETHE was operated. It limited the greenhouse temperature gain to just 2.5° C. Yield of tomato was 1.5 to 2 times, water used 44% of that in open-field. Water used was mostly for plants, only a small part was for foggers which were some times needed as supplement. ETHE and natural ventilation hold promise as environmental control devices for greenhouses in hot arid regions. [IIM A WP]