In hydroponic and soilless growing, the grower builds the root environment from scratch. There is no soil to buffer mistakes, so the water underneath the nutrient solution matters more than in field farming. This article explains why many growers use RO water, how electrical conductivity (EC) fits in, and the mistakes we see most often. Our hydroponics sector page shows how AFG systems fit.
EC in plain terms
EC measures how well water conducts electricity, which rises with the amount of dissolved salts. Growers use it as a quick measure of nutrient strength. But EC cannot tell nutrients apart from unwanted salts. If the source water already has a high EC, part of the target EC is taken up by sodium, chloride and other ions the plant does not want, leaving less room for fertiliser.
Why RO base water helps
Reverse osmosis removes most dissolved salts, giving a low-EC, consistent base. The grower then adds exactly the nutrients the crop needs. The recipe stays the same from day to day, EC control becomes easier, and salts do not accumulate in substrates. For many Gulf sources, where well water is brackish, RO is the only practical way to reach a usable base.
Blending
Where the source is only moderately saline, mixing RO permeate with raw water can reach the target base EC while keeping some useful calcium and magnesium. The blend ratio should come from the analysis and the crop, and can be automated.
Common mistakes
Looking only at total EC
A source with acceptable EC can still carry too much sodium, chloride or boron. Boron is a frequent problem: many crops are sensitive to small excesses, and standard RO does not always remove enough. Where boron is high, a second RO pass or boron removal stage is added. In one AFG project for a greenhouse in Ankara, boron in the well water was reduced from 2.8 ppm to under 0.1 ppm.
Forgetting what RO removes
RO permeate has almost no calcium or magnesium. If the nutrient recipe was written for a harder water, the plants may go short of these elements. Adjust the recipe when switching to RO.
Undersizing for peak demand
Greenhouse water demand peaks in hot weather. An RO unit sized for the average leaves the grower short on the hottest days. Size the unit and the storage for the peak season.
Skipping pre-treatment
Iron, manganese, hardness and suspended solids in well water foul RO membranes. Filtration and, where needed, iron removal ahead of the RO keep output stable and membranes clean.
Reusing drain water without disinfection
Recirculating drain water saves water and fertiliser, but it can spread root diseases across the whole crop. Drain water should be filtered and disinfected, for example with UV or ozone, before it returns to the mix. Sodium and other ions also build up over cycles, so some drain water has to be discharged.
Ignoring water temperature
Warm water holds less oxygen, and in Gulf summers nutrient tanks and pipes heat up quickly. Low oxygen at the roots slows growth and encourages disease. Shading and insulating tanks, keeping storage short and planning irrigation around the heat help more than any change to the recipe.
Not testing regularly
Check the EC and pH of the base water and the drain every day, and send samples to a lab from time to time to track sodium, chloride and boron.
A reference from our projects
AFG supplied an RO and ultrafiltration system with filtration for a banana greenhouse in Antalya, Türkiye, treating 36 m³/h, which is 864 m³/day. Each new system is sized from the grower's own water and demand, whether the farm is in the UAE, Oman or elsewhere in the region.
What to send us
A recent water analysis including EC or TDS, sodium, chloride and boron; the daily demand or growing area; the crop and growing system; and whether you want to reuse drain water. Send these through the quote form.