Fertigation and Dosing Strategies

Fertigation transforms irrigation from simple moisture replacement into real-time crop nutrition. In a soilless system with minimal substrate buffer, the concentration, pH and timing of each irrigation shot directly alter the root-zone electrochemical balance within minutes.

Modern commercial systems decouple stock tanks into Tank A (calcium nitrate, iron chelate, potassium nitrate), Tank B (potassium phosphate, magnesium sulphate, potassium sulphate, micronutrients), and Tank C (acid/alkali for pH regulation). Automated fertigation units inject concentrates in precise ratios into an in-line mixing manifold or batch tank before distribution.

Fixed-interval clock timers deliver identical water volumes on bright sunny afternoons and cool overcast mornings. On hot days with high light, plants consume water rapidly and run dry; on cloudy days, the same timer causes over-saturation, root hypoxia and wasted fertiliser.

Irrigation triggering methods

Commercial fertigation controllers trigger irrigation shots primarily through solar radiation accumulation (e.g. initiating a shot every 150–250 J/cm² of cumulative global radiation), supplemented by substrate moisture threshold sensors (TDR) and minimum/maximum time gates.

Root EC steering

When drainage EC rises significantly above dripper EC (delta > 0.8–1.0 mS/cm), the plant is absorbing water faster than nutrients, indicating high transpiration and salt accumulation. The grower lowers dripper EC or increases shot volume. Conversely, when drainage EC equals dripper EC, nutrients are passing unabsorbed, signaling low light, over-watering or low crop demand.

• Start the first irrigation cycle 1 to 2 hours after sunrise, once the crop has initiated transpiration and slab temperature begins to rise.
• End the final irrigation cycle 1 to 2 hours before sunset to allow the slab to achieve target overnight dry-back (8–12%).
• Measure input EC/pH and drainage EC/pH daily using handheld calibrated meters to verify controller accuracy.
• Install in-line disc or screen filters downstream of dosing units to prevent fertilizer precipitates from clogging drippers.

Modern automated fertigation incorporates feedback from drain EC and drain volume sensors. Closed-loop algorithms dynamically trim the next day's base EC and shot interval based on yesterday's total solar sum and drainage profile, maintaining target root-zone salinity with zero manual recalibration.