The first experiments in the new research centre for protected horticulture in Riyadh, Saudi Arabia, developed with support from Wageningen University & Research experts, show that water savings of over 90% can be achieved in local tomato growing.
Saving up to 90% water
The manager of the research facility Dr Khalid Al Assaf is very pleased by these early results. “The new research facility allows us to conduct precisely the type of research we have been aiming for. We can now make a comparison between the cultivation common in our country with the more advanced systems used in the Netherlands. Initial results show that we can save up to 30% of the water we previously consumed simply by deploying a mid-tech greenhouse system. In the high-tech greenhouse, we were even able to realise water savings of more than 90%. The results show that it is feasible to grow tomatoes in Saudi Arabia using a limited quantity of water, which would be a major leap forward.”
Three levels of technology are currently being analysed in the research facility in Riyadh:
- The ‘low-tech’ greenhouse is a simple plastic tunnel greenhouse cooled by a so-called pad and fan system using evaporating water. This type of greenhouse is commonly deployed for year-round production in Saudi Arabia.
- The mid-tech greenhouse has a glass covering and is also cooled using the pad-and-fan system, the difference being that the ventilation is regulated by frequency-controlled fans.
- The high-tech greenhouse is a closed system where the cooling and dehumidification is provided by coolers.
Exceptionally high yields
After 4.5 months of production, the yield of the low-tech greenhouse was 20 kg/m². Jouke Campen, a greenhouse horticulture expert at Wageningen University & Research, advises the research facility in Riyadh.
“This yield is exceptionally high compared to those commonly achieved in this type of cultivation system. It is mainly due to the covering of the greenhouse being new and very clean, transmitting a very large amount of the light to the crop. The fact that the soil in which the plants are growing has not been used for plant growth before is also beneficial.”
Production in the mid-tech greenhouse is similar to that of the low-tech cultivation system, although the light level is higher. The fact that the yield is comparable is primarily due to the fact that shading was applied at the start of the experiment to bring more balance to the crop’s architecture. The high-tech greenhouse produced a harvest of 30 kg/m², 50% more than the other two.
5 litres of water use instead of 168 litres
The low-tech greenhouse required 168 litres of water for one kilogram of tomatoes. The mid-tech greenhouse allowed for substantial water savings: only 108 litres of water were required per kilogram produced. Finally, the high-tech greenhouse showed extraordinary results, with only 5 litres of water needed for an equivalent production. This astounding water use efficiency can be explained by two factors: firstly, all the water transpired by the crop condenses in the coolers before being recycled and reused to irrigate the crop, and, secondly, cooling is carried out without any water evaporating.