PPP – Effectiveness of Pesticides depending on Water pH

Category: Agriculture | Tags: #  #  

In all branches of agricultural production whether it’s an open and protected production, arable farming, fruit growing or other branches, plant protection products are widely used.

In the fields, sowing, fertilization and protection of field crops are in full swing, and the first measures of phytopathogenic plant protection are being implemented in orchards and vineyards.

What everyone takes lightly is the quality of the water that will be used in the preparation of the plant protection product solution.

I would like to mention two main characteristics of water, on which the success of the application of plant protection products depends, namely:

  • pH
  • water hardness

Inadequate pH of the water and the solution of plant protection products can lead to decomposition and disturbance of the stability of the solution and reduce the effect.

Of course, the hardness of the water:  the higher the content of CaCO3 is in the water, the harder the water is and its composition negatively affects the effectiveness of plant protection products.

This negative effect is most pronounced with herbicides and is most visible immediately after application. Most pesticides are unstable in an alkaline environment and stable in a weakly acidic environment.

The effectiveness of insecticides is greatly reduced if water with a pH higher than 7 is used.

As an example we have that at pH8-9 the decomposition of insecticides is measured in minutes and of course the effectiveness is poor and different from the manufacturer’s recommendations.

In insecticides based on a.t. dimethoate stability at pH6 is 9 hours and at pH 9 is 48 minutes.
Fungicides based on a.t. captan stability at pH3 is 32 hours and at pH 8 is 10 minutes.
Herbicides used on maize and sugar beet crops are stable and effective at pH5 solution values and at higher values the efficiency decreases and degrades rapidly.

It is recommended that farmers use water of optimal pH value to mix most pesticides to pH 4.0 – 6.5.

Of course if the value of the pesticide solution is in the range of pH 6.5-7.0 treatment of target crops should be done immediately.

Of course, there are a number of different products on the market that are used to regulate the pH value and hardness of water in the preparation of PPPs to be maximally effective.

How to measure pH in PPP mixtures


pH Tester Groline 

The GroLine HI98118 pH/temperature tester is our latest pocket meter for measuring the pH of a hydroponic nutrient solution. This modern looking meter is only 0.7″ thick and extremely ergonomic, fitting comfortably in your hand. The HI98118 has a very large easy to read LCD display that shows both pH and temperature along with calibration, stability and low battery indicators. All operations are simplified to two buttons. One is for turning the meter on/off and the other for automatic one or two point calibration.


pH/EC/TDS/ Temperature Meter

With Multiparameter Probe HI9814 is a durable, portable pH, conductivity, total dissolved solids and temperature meter for most measurements encountered in hydroponics, aquaponics or general agriculture applications.

  • All operations and settings, are made through only two buttons
  • The housing is waterproof and rated for IP67 conditions
  • The supplied HI1285-7 multiparameter probe measures pH, EC/TDS, and temperature in one convenient, rugged probe.


Water hardness is one of the most common & one of the most significant pointers of general water quality.

In the following equilibrium reaction we can observe the dissolving and formation of calcium carbonate and calcium bicarbonate (on the right):

CaCO3 (s) + CO2 (aq) + H2O (l) ⇌ Ca2+ (aq) + 2 HCO3 (aq)

Ions causing permanent hardness of water can be removed using a water softener, or ion-exchange column. 

Classification hardness in mg-CaCO3/L hardness in mmol/L hardness in dGH/°dH hardness in ppm
Moderately hard
Very hard
≥ 181
≥ 1.81
≥ 10.12
≥ 181

How to measure water hardness?

There are several methods available, from fast checking test kits,  photometers to titration systems.

HANNA has developed a new “easy-to-use” solution for testing as an alternative to chemical test kits.

Checker®HC HI735

Hardness Low Range Checker

Features at-a-glance:

  • Easier to use and more accurate than chemical test kits
  • Dedicated to a single parameter
  • Small size, big convenience

The HI735 Checker®HC (Handheld Colorimeter) is a simple, accurate, and cost effective way to measure total hardness. Designed as a more accurate alternative to chemical test kits, the HI735 provides quick, accurate results in a few easy steps. Our Total Hardness Low Range handheld checker offers you a middle ground between advanced instrumentation and your typical chemical test kit.

Standard test kits have limited accuracy since they rely upon the human eye to match colors. Our handheld colorimeter eliminates the hassle of matching to a color chart by providing a direct Total Hardness Low Range result digitally.

  • Range: 0 to 350 ppm (mg/L) as CaCO₃
  • Get simple results with easy one-button operation.
  • Don’t waste time matching to a color chart anymore, get direct results quickly.


Total Hardness Portable Photometer

The HI97735 Total Hardness Photometer combines accuracy and ease of use in a simple, portable design. The advanced optical system provides lab-quality accuracy while its user-friendly design is easy for any user making it the perfect photometer for your water quality testing needs. The HI97735 meter measures total hardness in water samples up to 750 mg/L (ppm) CaCO3.

  • No warm up time needed before taking a measurement.
  • Tutorial mode for easy step-by-step instructions.
  • CAL Check for performance verification and calibration
  • Easy navigation between chemical forms with a press-of- a-button:

– mg/L (ppm)

 – French degrees (°f)

 – German degrees (°dH)

 – English degrees (°E)

Available in 2 versions :

HI97735 Basic – photometer only

HI97735C Set – photometer in carrying case with standards

Reagents & ranges guidelines:

HI93735-00  (100 tests) LR –  low range – 0 do 250 mg/L (ppm) CaCO₃; 0-14dH

HI93735-01   (100 tests) MR – middle range – 200 do 500 mg/L (ppm) CaCO₃; 11-28dH

HI93735-02  (100 tests) HR – high range – 400 do 750 mg/L (ppm) CaCO₃; 22-42 dH

*also available as full set HI97735-0 (LR+MR+HR)

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