Where Does The Water Come From ?

Soil Zone Sand and Gravel Aquifer Limestone or Granite Aquifer Sandstone Aquifer Examples of Variation in Groundwater Quality Well # 1Well # 2Well # 3

Frequency % Irrigation Water Alkalinity concentrations (ppm CaCO 3 ) from Florida <40 40– >400

The Goal Is To Achieve A Stable Medium pH Over Time

Plant Growth Cycle Active Growth Establishment Mature

 pH affects the solubility of fertilizers, and the efficacy of pesticides and growth regulators.  the higher the water pH the less soluble these materials are pHpH

pH Drift Alkaline Water pH NH 4 + fertilizers Time “Optimum” Range

A measure of water’s ability to neutralize acids – a buffering ability A measure of water’s ability to neutralize acids – a buffering ability Mostly carbonates and bicarbonates – associated with Ca and Mg (limestone) Mostly carbonates and bicarbonates – associated with Ca and Mg (limestone) May cause pH to rise in media over time, especially in small containers May cause pH to rise in media over time, especially in small containers AlkalinityAlkalinity Note: Alkalinity “controls” pH Must know alkalinity to manage pH

Expressed in ppm, mg/L, meq/L Expressed in ppm, mg/L, meq/L Expressed as CaCO 3 or HCO 3 - Expressed as CaCO 3 or HCO 3 - AlkalinityAlkalinity Irrigation water should have an alkalinity of less than 100ppm; if higher than 150 ppm, acidification is needed Irrigation water should have an alkalinity of less than 100ppm; if higher than 150 ppm, acidification is needed

CaMg(CO 3 ) 2 Dolomitic limestone Ca 2+ + Mg CO 3 2- Hardness Alkalinity Hardness and Alkalinity Generally Go Hand-In-Hand but They Are NOT One and the Same You Can Use the Water Hardness to Estimate Its Alkalinity

Alkalinity Terms Milliequivalents alkalinity mg/liter or ppm CaCO 3 of alkalinity mg/liter or ppm bicarbonate

H 2 CO 3 2CO H + H 2 O + CO 2 Substrate Acidity Alkalinity Both the alkalinity and the acidity are neutralized

Sample A Sample B pH = 9 pH = 7 One drop of acid to get pH 6 Ten drops of acid to get pH 6 The Effect of Water Alkalinity on Media pH and Acid Requirement Little or no effect on the growing medium pH Increases growing medium pH Alk = 50 ppm Alk = 300 ppm

Action Steps To Correct High Alkalinity reverse osmosis acid injection acid fertilizer and/or none less lime Alkalinity (ppm) bicarbonate

Salinity Salinity is measured by Electro-conductivity  Total Dissolved Salts (TDS) – all salts present in the water (1 mMho/cm=640 ppm)  less than 0.75 mMho /cm for plugs  less than 1.0 mMho /cm for other greenhouse crops  less than 2.0 mMho /cm for other nursery crops

Testing The Soil Solution !

Simple technique for measuring pH and EC Simple technique for measuring pH and EC Charts for recording pH & EC Charts for recording pH & EC Guidelines for crops Guidelines for crops Procedures to keep on track Procedures to keep on track Pour Thru Method

6 or 8-inch saucers are adequate for collecting the leachate

Distilled Water Volumes 4 inch 5 inch 6 inch 6.5 inch 1 Qt 4 Qt 12 Qt Pot Size mloz

Flats: Use 50 ml Distilled Water

EC Comparisons 0 to to to to to 2.3 > 2.3 1:2SME PourThru Indication 0 to to to to to 6.0 > to to to to to 7.8 > 7.8 Very Low LowNormalHigh Very High Extreme

Initial EC

Crop pH Ranges

Geraniums (6” pinched) 1/28 5/ to to to 6.0