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Chemical Injection

One of the great advantages of liquids is their ability to act as carriers for additional products such as micronutrients, fungicides, inoculants, soil wetters etc. UAN (32:0:0 or 28:0:0) is commonly used as the carrier for these products as well as dilute phosphoric acid or water. Dosing of additional chemicals into the main carrier liquid is usually achieved by one of the following methods.

Tank Mixing

METHOD
Introduce the additive products into the main tank in appropriate volumes and mix as a batch. Make sure that products are compatible!

PROS
Simplest method of adding chemicals to your main carrier liquid.

CONS
Normally, enhanced tank agitation is essential. Liquid Systems has rate control modules with larger pumps (e.g. Ai120, 1126) to provide additional flow for agitation.
Ratio of added chemicals to carrier liquid is fixed. This may be undesirable or wasteful if variable rate control of main carrier is required.
Potential wastage of expensive chemicals when there is leftover liquid in the tank at completion of sowing a crop.
No independent rate control for the injected chemicals.

Percentage Based Mechanical Dosing Devices

METHOD
Mechanical Dosing systems are a means of introducing products to the carrier liquid on the go. Typically they are positive displacement mechanical devices activated by the flow of the carrier liquid and adjusted manually to a percentage of the flow.

Such devices generally have percentage ranges (eg. 0.2-1.6%, 0.5-2.0%, 1-10%, 5-20%) of carrier flow.  Precise carrier rates are essential for these systems to function correctly as dosing rates are inextricably tied to carrier rates.

The devices are put inline with the main carrier output line and draw the chemical from a separate tank.

PROS
Relatively inexpensive and simple to setup.

CONS
Difficult to monitor whether the device is operating correctly, or at all. Especially at night.
No way to monitor the actual rate being applied.
Manual adjustment is required to change the rate. I.e. variable rate control of the injected chemical.
Variable rate control of main carrier forces rate adjustment of added chemical. No independent control of the injected chemicals.
Additional agitation system for the dosing products tank will be required if multiple products are injected at once using a single device?
Pulsing created by these mechanisms may impact the stability of the rate control of the primary carrier liquid.

Electronic Dosing. (Variable Rate Technology)

METHOD

This is the most advanced method of chemical dosing and involves using an electronic control system to control flow of chemicals injected into the main carrier output. The rate the injected chemical is controlled independently to the main carrier liquid.

GPS map based prescriptions can be used to precisely apply liquid fertilizer and injected chemicals at varying rates independently of each other according to soil and crop requirements and label specifications of the injected chemicals.

Example: A farmer applies UAN with a variable rate system where rates could continually vary between 30 l/hectare and 70 l/hectare and where the requirement for Zinc application may be a steady 3 l/hectare or variable 3-5 l/hectare.

The Liquid Systems (SA) Spiker product has been designed specifically for this purpose.

PROS
Independent variable rate control of injected chemicals provides greater efficiency and effectiveness of the injected chemical.
Less wastage of chemicals.
$ savings through more efficient use of chemicals.
Treat adverse soil conditions appropriately according to need and independently to the rate of fertilizer applied.
Continuous monitoring of the
Traceability of chemical application by recording actual rates applied with Precision Ag systems (Greenstar™, Ag Leader, Topcon, Trimble)
Change rates at the touch of a button.

CONS
While an electronically controlled system will require a larger initial investment, the flexibility, efficiency and improvement in effectiveness of the chemicals applied makes it worthwhile, especially for those customers implementing variable rate cropping regimes.