FERTIGATION SYSTEMS AND NUTRIENT SOLUTIONS - NUTRIENT DELIVERY SYSTEMS & SOLUTIONS

R NUTRIENT DELIVERY SYSTEMS

1. Simple systems: Non-recirculating/air gap system or the raft system where the roots hang down directly into the nutrient solution. Basic wick system in which the nutrient solution is drawn up by an absorbent wick into an aggregate where the roots grow.
2. Complex systems: The flood and drain, top feeder, NFT or Aeroponic systems all of which require pumps to move the nutrient solution from a reservoir or series of tanks to the plants via PVC, poly and drip tubing, emitters, etc.

NUTRIENT SOLUTIONS

The importance of good quantity/quality water for hydroponic plant production:

Any hydroponic nutrient solution begins with the “source water”. A grower can obtain source water from:

1) City water supply 2) Private wells 3) Water harvesting (channeling rain water into catchments)

The source water must have the appropriate quantity and quality:

Quantity: There must be sufficient water available for plants and for cooling. Ex: For tomatoes in greenhouse hydroponics: ~4 liters/plant/day or if 2.5 plants/m2, then 10 liters/m2/day.

If evaporative cooling is used, especially in desert areas, water needs may be doubled!

Quality: Factors to consider include pH, EC (salt levels) and contaminants:

1) pH: The p(Potential of) H(ydrogen): Acid or base character of the water. pH = - log [H+] (neg. log of the H+ conc.) Scale = 0-14 Ex:

• If [H] = 10-7, then pH = 7 (Neutral)
• If [H] = 10-4, then pH = 4 (Acidic)
• If [H] = 10-9, then pH = 9 (Basic)

Ways to test the pH: Litmus paper (color change), pH meter (analog or digital)- meas. [H+]

For most plants: pH 5 – 7. For tomatoes: 5.8 – 6.3. Above pH 7 may cause problems with nutrient uptake. Below pH 5 may cause abnormal absorption of certain ions resulting in deficiencies or toxicities.

2) EC (Electrical conductivity): a measure of the total salts in water. Pure water (no salts) does not conduct electricity: EC = 0. The higher the salt levels, the higher the EC. Measured in: mS/cm (milli-Siemens per centimeter)

3) TDS (total dissolved solids): For tomatoes: EC = 2.5 – 3.5 mS/cm (depends on light, plant architecture desired, etc.)

Elevated salt levels: Certain geographic areas have high salt levels in the water :

• High boron, fluoride, chloride, sulfates and sodium: -Can cause poor plant growth. -May influence soluble salt levels in the water.

• High iron, especially in “hard water” (having high Ca and Mg): -Can cause rusty spots on leaves with overhead irrigation.

• High salt levels can also cause rapid salt buildup on cooling pads. -May need to bleed off and replace pad water regularly.

Heavy metal contaminants: Certain geographic areas have high levels in the soil and/or water. High lead, cadmium, aluminum, silver, etc.: -May be excluded or absorbed on a limited basis by plants. -May be absorbed and stored (but not toxic to the plants).