1. presented by
Burrell Scarlett
EVERGROW HORTICULTURAL PRODUCTS

2. Irrigation Water Quality
Management
Fertilizers, Pesticides & Drip Irrigation
Performance

3. The efficacy of fertilizers and pesticides are significantly
affected by the quality of the water used to apply these
chemicals. Bad Water Quality, as it relates to Acidity and
Alkalinity can determine how long pesticides remain effective
in solution or whether plant roots will absorb nutrients.
Further, low quality water will quickly block drip irrigation
emitters.

4. PESTICIDE USE
Pesticides are normally formulated as weak acids or neutral to
weakly-alkaline products. As a general rule, herbicides,
insecticides, and fungicides perform best in slightly acidic
water, pH 4–6.5. When water pH falls outside of the preferred
upper or lower boundaries, product performance can be
compromised. In some cases, the pesticide can fall out of
solution. The pH of the solution can also influence how long a
pesticide molecule remains effective or be
degraded/hydrolyzed.

5. Product Half-Life
pH 9 pH 7 pH 5
Herbicides 10 minutes 17 hours 16 days
Fungicides 2 minutes 3 hours 10 hours
Insecticides 24 hours 10 days stable
HALF- LIFE …..(time required for a product to loose 50% of
its effectiveness)

6. Each pesticide has its specific pH range at which it works best
but the following general rules will suffice for most pesticide
spray solutions:
• A pH between 3.5 and 6 is satisfactory for most spraying and
short-term (12–24 hours)storage of most mixtures in a spray
tank. Not suitable for sulfonylurea urea herbicides.
• A pH between 6 and 7 is adequate for immediate spraying for
most pesticides. Do not leave the spray mixture in the tank for
more than 1–2 hours, to prevent loss of effectiveness.
• Most products mixed in alkaline water should be sprayed
immediately.
For more information on Pesticide Breakdown Rates visit:
www.nutri-tech.com.au/.../Pesticide%20Breakdown%20Rates.pdf

7. BLOCKAGE OF DRIP IRRIGATION EMITTERS
There are three types of clogging hazards that need to be considered in
the design and maintenance of irrigation systems. These are physical,
chemical and biological. All depend on Irrigation Water Quality.
Clearing of chemically blocked drippers may be done by use of acids
or by a bacteria, Agrobacterium FS-16 which dissolves CaCO3
precipitates. The use of acid injection (sulphuric and or phosphoric
acid)or water conditioner to treat chemical deposits (carbonates,
hydroxides and phosphates) in drip irrigation systems is common
amongst growers.

8. Since the solubility of Calcium carbonate is reduced as water
temperature increases….do early morning treatments Set pH of
cleaning water solution to 4 for 60 minutes or 2 for 15minutes
in the drip lines.
Flush with pure water after this treatment.
Calcium carbonate is the main chemical deposit which blocks
drip irrigation emitters.

9. FERTILIZER USE
Plant roots will not absorb fertilizers efficiently if the pH range is
not optimized i.e. soil and irrigation water pH affect the
availability of all mineral nutrients. Figure 1 below shows that the
absorption of all essential nutrient elements is optimized at pH 5.5
- 6.5. The feeding of specific elements as supplements should be
done within their specified range as indicated below. Example,
Molybdenum is best applied within an alkaline solution of pH
greater than 7, whereas Manganese is best applied in an acidic
solution of pH less than 5.5.

10. Figure 1: Influence of nutrients uptake by pH

11. Fertilizer Use Efficiency
NUTRIENTS
Fertilizer Use Efficiency (%)
Soil application Fertigation*
N 30-50 95
P 20 45
K 50 80
* 95% applied fertilizers taken by plants

12. FIXING OF PHOSPHATE FERTILIZERS
(precipitates)
Acid soils
8 Fe and Al phosphates
FePO4
l2H2O, AlPO4
l2H2O
Alkaline soils
4 Ca and Mg phosphates

13. Nomenclature
H3PO4 = phosphoric acid
H2PO4
- = monobasic
HPO4
-2 = dibasic
PO4
-3 = tribasic

14. Inorganic P Compounds
 Ca(H2PO4)2
 monocalcium phosphate
 CaHPO4
 dicalcium phosphate
 Ca3(PO4)2
 tricalcium phosphate
 3Ca3(PO4)2
lCa(OH)2
 hydroxyapatite
 3Ca3(PO4)2
lCaCO3
 carbonate apatite
decreasing solubility
pH
6
8

15. Phosphate Reactions at High pH Values
* P converts to less soluble
Ca and Mg compounds
Ca(H2PO4)2 + CaCO3 + H2O  2 CaHPO4
2H2O + CO2
very less
soluble soluble
6 CaHPO4
2H2O + 3 CaCO3  3 Ca3(PO4)2 + 3 CO2 + 5 H2O
less
soluble
3 Ca3(PO4)2 + CaCO3 3Ca3(PO4)2
CaCO3
very insoluble
- most serious in calcareous soils of arid regions

16. PHOSPHATE FERTILIZERS
PO3−
4 HPO2−
4 H2PO−
4
In dilute aqueous solution, phosphate exists in four forms.
For Solubility:(H3PO4) H2PO−
4>HPO2−
4>PO3−
4
(H2PO4)− is most common , and most soluble at about pH 5.5
(H2PO4)− is mostly available as, Mono-Ammonium Phosphate, MAP
or Mono-Potassium Phosphate, MKP and used extensively in fertigation.
In soil cropping, the compound superphosphate, Ca(H2PO4)2 is a very
common fertilizer producing phosphorus to the plant.
Ca3(PO4)2 + 2H2SO4 = Ca(H2PO4)2 + 2CaSO4

17. In summary, to optimize the use of phosphate
fertilizers, the grower must manage irrigation
water pH.

18. Phosphate Ion: Protonation
acid soils alkaline
soils

19. CORRECTING THE pH
Irrigation water and water used for mixing pesticides are usually
alkaline and therefore not suitable for direct use. Acid based
compounds called water conditioners or acidifiers are usually
used to lower the pH. A bacteria, Agrobacterium FS-16 is also
able to dissolve CaCO3 precipitates.
•EVERGROW WATER CONDITIONER reduces the pH of the
water to proper levels suitable for pesticide and fertilizer
solutions.