On Estidamah, the Low-tech greenhouses are single-span pad and fan-cooled high tunnels. The medium-tech greenhouses are tall, multi-span, glass-covered greenhouses with a soilless growing system, a heating system and a controllable shade screen. The Medium-tech greenhouses are also pad & fan-cooled. The High Tech greenhouses are also glass cladded, tall greenhouses. Instead of a pad and fan cooling system, the Hi-Tech greenhouses are equipped with air conditioning, which allows to seal the greenhouse environment from the outside air. Because of this sealed environment, CO2 can be injected to elevate the inside concentration to 800 ppm that promotes production. High technology level makes the greenhouse more expensive, of course, which has to be paid back from additional production value and from savings on resources. In Saudi Arabia, water consumption can be diminished by the application of high-tech greenhouses to increase production. On the other side, expenditures on electricity go up with increased technology level, just as the capital costs.
Experimental History
- Seed Sowing: 12 June 2017
- Transplanting: 8 July 2017
- Plant density: 2.5 plants per m²
- Harvesting Period: 3 September 2017 – 25 March 2018 (29 weeks)
Obtaining bench mark figures for production levels and consumables for three tomato greenhouse technology levels
- Three greenhouse technology: Low, Medium and High
- Two cultivars: Dafanis and Cluster (RZ)
- Water consumption for irrigation and cooling is about 88 liter/kg in Low-tech, 47 liter/kg in Medium Tech and 2.5 liter/kg in High Tech greenhouses.
- In Air Conditioning cooled greenhouse, 95% of the water transpired by the crop can be re-used, so almost no water loss
- Electricity consumption is 1.2 kWh/kg for Low-tech, 2.4 kWh/kg for Med-tech and 12 kWh/kg for High-tech greenhouses
- Hi-Tech greenhouses can only be economically viable at low electricity price (< 0.15 SAR/kWh) and or high costs for water (> 1 SAR per m³)
Recommendation
- High Tech greenhouse production is a capital-intensive production system that needs a high turnover and throughput to be economically relevant. Good arrangements with customers on price and quality are therefore crucial.
- The very dry outside air conditions in the Riyadh-region allow for good evaporative cooling. Despite the high outside temperature and radiation levels, pad and fan cooling provide a favorable inside climate for growing tomatoes.
- With the current water and electricity prices, from an economical point of view, a medium-tech greenhouse is the best option.