Liquid nutrient solution is added to the water in the tank, which will be pumped around the plant roots. Only a small volume of nutrients is needed - typically 5 ml per litre of water, but this can vary based on the crop you are growing. Depending on whether the plants need more water, or more nutrients, the concentration of nutrients in the tank will go up or down. Maintaining the correct nutrient concentration will give you faster growth, healthier plants and a better yield.
Nutrient concentration
Nutrient concentration is measured in a number of ways, but they all relate to the same thing; it’s the proportion of nutrients to water. Some people use “Parts Per Million” (PPM), some use “Total Dissolved Solids” (TDS), and some use “Electrical Conductivity” (EC).
A sensor is provided with the Harvst grow system which gives you the EC reading. Most indoor veg, salads and leafy greens require an EC level of between 1.0 and 1.6 - it’s not a precise value, and can vary with temperature (even though the sensor is temperature compensated), so being within +/- 0.3 of the target EC is fine.
If your H-series is online and connected to your Harvst web account, you can get alerts when the EC level goes above or below set values. This will remind you to adjust the nutrient concentration.
Nutrient temperature
Plants need their roots and water to be warm enough, but they don’t like it too warm. The Harvst nutrient sensor will also tell you the nutrient temperature.
If it’s consistently too warm (over 25°C), you will need to consider moving the system to a cooler place, or if it’s a real problem (perhaps in a shed in the summer) you can circulate the water through a larger tank to keep it cool.
If it’s too cold (below 10°C) you can fit an extra heater pad under the tank. This is available as an optional extra.