Multi-product mixtures are common in modern farming, and so are unpredictable weather patterns that increases the requirement to spray large areas in a short period, with zero tolerance for down-time caused by problematic tank mixtures.
To make matters worse, slight formulation differences in the same brand from batch to batch could mean that the same product can behave differently in a familiar mixture. This is particularly common in generic versions where the active ingredient or other raw materials are sourced from different suppliers – depending on who is the cheapest.
Given that the above variables are usually not within our control, here are ten proven practices that can be employed to reduce the risk of failing spray mixtures and costly mistakes.
Using good, clean water
Ideally 10 degrees or warmer, with low dissolved minerals and hardness, close to neutral pH, with no suspended organic materials.
Make sure the entire spray system is clean and properly decontaminated from the preceding spray
In particular, flush out solid or flaky deposits that may accumulate on filters or nozzles before use. Filters should be replaced annually - particularly if granular products are commonly used.T he different types of cleaners include;
- Boom Tank Cleaner (does not contain chlorine), which is a good general purpose tank cleaner for routine cleaning and when preparing the sprayer for storage. It decontaminates most pesticide residues, removes stains, crystalline deposits, and protects against corrosion.
- Kleenup Granular (contains chlorine), which is a multipurpose decontaminant for most pesticide residues including sulfonylurea and phenoxy herbicides. It contains a blue tracer to indicate when the system is completely flushed.
Fill the tank 50 percent (pc) with water before adding products
Condition the water as required by the intended mixture
Most products (unless specified otherwise by the label) are stable in mildly acidic solutions (pH 4.5 to 6.0). Depending on the spray mix, there are several adjuvants that could be added to condition and/or acidify the solution for optimal performance and stability. These do not replace the adjuvant as recommended on the product label – they are commonly used in addition to improve the quality of the spray mixture. Some of these adjuvants/agents include:
- Suspend is a coupling agent and water conditioner that improves compatibility of complex mixtures, including mixtures with liquid nutrients and fertilizers. It conditions hard and alkaline spray water to a mildly acidic pH and helps to prevent incompatibility.
- Ammend or Spray Grade AMS are ammonium sulphate water conditioners designed for use with glyphosate-based herbicides to minimise antagonism and improve performance under adverse conditions.
- Companion and Cohort 700 are acidifying and penetrating surfactants for use with herbicides. They also assist with the uptake of liquid fertilizers and mitigation of spray drift by reducing the number of fine droplets in the spray mix.
- Partner 950 is an adjuvant for glyphosate and glyphosate mixtures with wetting and penetrant qualities. It also acts as a water softener and acidifier to reduce alkaline hydrolysis.
Maintain good agitation throughout the entire process
Do a jar test if unsure about the physical compatibility of mix components
When changing brands or spraying a new combination of products for the first time, a simple jar test should indicate physical compatibility and prevent large-scale problems later.
Use the correct mixing order
Products with low water solubility need to be added to the mix first. After filling the tank 50 pc and with water still running into the tank, the suggested mixing order is:
- Water conditioners, acidifiers and Coupling agents
- Wettable powders (WP)
- Water dispersible granules (WDG) or dry flowable (DF)
- Flowable or suspension concentrates (SC)
- Wetters (if using Emulsifiable concentrates)
- Emulsifiable concentrates (EC)
- Water soluble liquids (e.g. SL, EW, SE)
- Adjuvants and Oils
- Liquid UAN
Be patient, particularly when adding individual mix components
Allow time between additions, particularly when mixing in cold water. Ensure slow-to-dissolve formulations are fully in suspension before adding the next. Agitate during loading and don’t dump granules into water volumes that are too small.
Whilst spraying or during filling, periodically inspect the agitation system and potential points where blockage may occur e.g. filters and nozzles
Avoid leaving a mixed solution in the spray tank for prolonged periods
If conditions suddenly change to become unsuitable for spraying, continue to agitate the unused spray mixture at a low level to keep it in suspension. Leaving a spray solution overnight should be avoided. However, if there is no other option continue low level agitation or agitate at regular intervals to prevent the mixture from settling.
Buffered or pH-conditioned spray mixtures will reduce chemical breakdown and/or alkaline hydrolysis in the standing tank. So, be sure to always add an adjuvant to maintain the required pH of 4.5 to 6.0 as standard practice.
When spraying with the aged mixture resumes, it is a good idea to mark the exact spot in the paddock where it starts. This will provide clues in case chemical breakdown resulting in reduced pest and weed control occurs.
This article was written by DKSH for Seasons magazine.
Please note: this article contains information of a general nature, and does not take into account your personal objectives, situation or needs. Before acting on any information, you should consider the appropriateness of the information provided, and seek advice on whether it is fit for your circumstances.