Category: Mixing

All hort articles about water quality, agitation, tank mixing and adjuvants.

Sprayer Loading and the Jar Test

The time and attention spent during sprayer loading is a worthy investment. It ensures that the products in the tank perform as intended and reduces the chance of incompatibilities.

The label

Pesticide labels are always the first point of reference. Labelled mixing instructions should be obeyed even if they contradict conventional practices (see Mixing order, below). Consult this article on tank mix compatibility for more information on how to quickly and easily consult labels for each of your tank mix partners.

The carrier

Typically, the carrier is water, and understanding its role in pesticide performance is another article (or several). We’ve provided some links here for further reading.

Take some time to read Les Henry’s 2016 Grainnews article called “The Coles Notes of Water Chemistry“.
You can also read about pH and water hardness. It should be noted that pH and the resultant hydrolysis that can affect product half-life is typically an insecticide issue (not fungicide or herbicide). The famous fungicide example is Captan, which has a half-life of 32 hours at pH 5, but only 10 minutes at pH 8. Michigan State did a great summary (in 2008 and on US product formulations) which you can find here.
Finally, learn how to read a water quality report, here.

Carrier volume

Products dissolve better in higher volumes. The sprayer tank (vat, inductor, etc.) should be at least ½ full or water before adding the first product. In the case of a fertilizer carrier, it may look like water, but it contains high levels of salts that tie up free water and reduce solubility. For fertilizers, a higher initial volume of ¾ full is required.

The incomplete dissolution of products can leave hard-to-clean residues, plug fluid lines, and result in a non-uniform application that reduces efficacy. The risk of incompatibility is greater with low carrier volumes and high product rates (especially dry formulations). This is a common problem in regions that use low water volumes to apply multiple tank mix partners.

Carrier and product temperature

Both carrier and product temperature affect mixing. Imagine mixing sugar in hot tea versus iced tea – more sugar dissolves more quickly in hot liquid. Here are three common temperature-related issues:

Dry formulations and liquid flowables take more time to disperse (consider using a pre-mixed slurry).
Emulsified concentrates and oil might form gels rather than milky blooms.
Water soluble packages might not dissolve completely and could plug filters and nozzles – or clog the pump intake.

Note the undissolved residue collected on these swatches of red filter material. Products dissolve faster and better when carrier and products are warmer.

Note: Water and fertilizer are very different carriers. Beware of carrier-specific incompatibilities

Agitation

Keep agitation running throughout mixing and spraying. Aim for a “simmer” on the liquid surface rather than a “rolling boil.”

Low agitation can cause products to settle, making them difficult or impossible to resuspend later. Conversely, aggressive agitation (especially in half-full tanks) can cause foaming, pump suction loss, or product separation / clumping.

Pace

Adding products too quickly can cause product separation / clumping or poor suspension, leading to tank mix incompatibilities. While loading quickly improves operational efficiency, complex mixes require patience; Sometimes over five minutes between additions, especially in cold water or when using dry products.

To save time without sacrificing quality, consider pre-hydrating dry products or using a separate nurse tank to pre-mix loads for quick transfer. Remember: even if dry products look dissolved, they may still need more time.

Product formulation

Product formulation is a complicated science. In the 1950’s a formulation might have three active ingredients and an inert filler. See the historic formulation index card shared by Dr. M Doug Baumann (formally with Syngenta, Honeywood).

Today, a product can include as many as 40 ingredients with formulation testing lasting two to four years! Generally, only 25% of the volume is water, 50% is active ingredients and the remaining 25% is co-formulants. This is why the more products you add to the tank, the higher the risk of antagonism. This is also why operators should carefully consider the cost benefit of generics, which may include the active ingredient, but do not tend to include the co-formulants.

Illustration based on a slide by Dr. Samantha Francis, Formulation & Application Technology Lead at the Syngenta Honeywood Research Facility.

Mixing order

Tank mixing order is critical for chemical compatibility. While common acronyms like w.w.w.W.A.L.E.S., W.A.M.L.E.G.S., and A.P.P.L.E.S. serve as reliable guides 95% of the time, always defer to the pesticide label for specific instructions.

Expanded generic mixing order:

Water: Fill tank 1/2 full (or 3/4 if fertilizer carrier).
Agitation: Engage to fully disperse dry products.
Water-Soluble Bags (WSB): Allow to fully dissolve.
Wettable Powders (WP)
Water Dispersible Granules (WDG, WG, SG)
Liquid Flowables (F, FL, SC, SE, CS, DC, EW)
Emulsifiable Concentrates (EC, MEC, OD)
Solutions (SN, SL, Liquid Fertilizers/Micronutrients)

Adjuvants:

Water Conditioners (e.g. anti-foamers, compatibility agents): Add before pesticides.
Activator Surfactants (e.g. NIS, COC): Add after pesticides or by formulation type along with pesticides.
Drift Retardants: Add last.

Examples of mixing errors

Micronutrients like sulfur (e.g. ATS) added to nitrogen-based formulations (e.g. UAN) can cause physical incompatibilities. This became a problem during “weed-and-feed” applications in Ontario corn in the late 2010s, and working with the registrants, we found a solution.

What follows is not only a good example of why mixing order is critical, but why growers should get into the habit of performing jar tests. Learn more about a real-world ATS example here.

**Left:** ATS and UAN premixed, followed by Primextra created curds.
**Centre:** UAN, followed by low-load ATS followed by Primextra worked.
**Right:** UAN followed by Primextra followed by high-load ATS worked.

Mixing errors are just as likely in small plot work as in commercial sprayers. Watch this short video by Mike Cowbrough describing hi experience with mixing order for Elevore and glyphosate.

The jar test

A jar test is a small-scale version of tank mixing used to check for physical incompatibility. Always wear PPE and work in a well-ventilated area away from ignition sources.

Jar test steps:

Prepare: Read all labels for formulation details, water quality requirements (pH/hardness), and mixing order. Shake liquid containers to ensure consistency.
Initial Carrier: Fill a 1-litre glass jar with 250 ml of water (or 375 ml if using oil/fertilizer).
Add Products in Order: Add chemicals following the standard mixing sequence, stirring constantly. Scale rates to match your tank concentration (e.g., 1 kg per 1,000 L equals 0.5 g in a 500 ml test).
Wait and Observe: Allow 3–5 minutes between additions—especially for dry products—to ensure full dispersion. If testing water-soluble bags, include a small piece of the film.
Final Volume & pH: Top the jar up to 500 ml with your carrier. Check the pH with a digital meter and add adjusters if required by the label.
Evaluate: Let the jar stand for 15 minutes.

The mix is likely incompatible if it generates heat, forms gels or scum, or if solids settle out (excluding wettable powders). Note: Jar tests only identify physical issues; they do not guarantee biological efficacy or crop safety.

Compatibility kits

When performing a jar test you must maintain the same product-to-carrier ratio as in a full-sized sprayer tank. This math is made easier with commercial compatibility kits such as the one from Precision Laboratories (below).

Compatibility Test Kit: Five pipettes, three bottles, gloves, instructions. ~$10.00. (Photo: Precision Laboratories)

Such kits contain a few plastic “jars” and disposable micropipettes. By following the instructions included with the kit, you can easily reduce large labelled volumes (e.g. 1 kg of product in 1,000 litres) of multiple products to small volumes at the same ratio. In this case we assume the final volume would have been 1,000 L, and so we reduce all the quantities accordingly to get 500 ml. The following mixing order is provided as an example.

Order	Ingredient	Quantity for 500 ml or 500 g of product labeled for 1,000 L of final spray volume
1	Compatibility agents	5 ml (1 teaspoon)
2	Water soluble packets, wettable powders and dry flowables. Include a 1cm2 cutting of PVA packaging.	15 g (1 tablespoon)
3	Liquid drift retardants	5 ml (1 teaspoon)
4	Liquid concentrates, micro-emulsions and suspension concentrates	5 ml (1 teaspoon)
5	Emulsifiable concentrates	5 ml (1 teaspoon)
6	Water-soluble concentrates or solutions	5 ml (1 teaspoon)
7	Remaining adjuvants and surfactants	5 ml (1 teaspoon)

Records and delayed reactions

Maintain detailed mixing records for traceability and to track performance. These records help you replicate successes and avoid future failures.

Labelled jar tests are also valuable; by leaving them in the chemical shed overnight, you can see if products separate or solidify over time. This indicates whether a mix can safely sit in the sprayer or if it requires immediate rinsing. For example, one grower’s Enlist and Manzinphos mix appeared fine until it sat during a rain delay. It turned into “lard,” clogging the entire system and requiring a manual teardown. They even had to dig some of the substance out with screwdrivers (see the picture of the filter below). An overnight jar test likely would have predicted this problem.

Some physical incompatibilities are not immediately apparent. This occurred overnight while the partially-full sprayer waited out a rain event.

Closed transfer

As a brief mention, an expansion of closed transfers systems for loading pesticides is on the horizon in North America. They have great potential to make loading more efficient, reduce operator exposure and reduce point-source contamination. Depending on the design, however, the operator may not be able to open pesticide containers to obtain samples for jar testing. This would be a great loss.

For more information

Learn more about physical and chemical incompatibility in our article on Tank mix compatibility. Be sure to download a copy of Purdue University’s 2018 “Avoid Tank Mixing Errors”. Finally, if you have questions about a specific product, contact the manufacturer, who have likely already performed the testing with common tank mix partners and can advise you.

This article was co-written with Mike Cowbrough, OMAFA Weed Management Specialist – Field Crops

May 6, 2026

Spray Water pH

The scuttlebut on coffee row is that acidifying a spray mixture improves its efficacy. There are also claims that pesticides break down in the sprayer tank if the pH is too high.

But it’s not that simple. Low pH has a strong impact on pesticide solubility, and that means mixing and cleanout are affected. Acidifying the mixture can have profound negative effects for many products.

It’s important to know what you’re doing.

What is pH?

pH is defined as the negative log of the molar concentration of hydrogen ions in a water-based solution. The more abundant the hydrogen, the lower the pH. It’s a log scale, so every unit of pH refers to a 10-fold change in the concentration of hydrogen ions.

Both very low (acidic) or very high (basic) pH can be caustic. But having a low or high pH doesn’t mean it will burn your skin or clothes right away, it might just be a bit unpleasant. But at the extreme ends, protection is needed.

Why is pH Important in Spray Mixtures?

In spraying, the main effect of pH is on the pesticide’s solubility. Solubility matters when mixing and becomes important during cleanout as well.

A minor effect on pH, at least for herbicides, is on chemical breakdown, usually through hydrolysis, when the pH is too high. The effect on breakdown is rarely meaningful during any given spray day, but may play a role if a spray mix is stored overnight or longer.

The Basics: Strong vs Weak Acids

Strong acids like hydrochloric acid (HCl) ionize completely in solution. When added to water, only H⁺ and Cl^– are present, there is no HCl. The water’s pH does not affect solubility of a strong acid.

But weak acids do not completely ionize. The water pH affects the degree of ionization and therefore solubility.

Most herbicides are weak acids. A weak acid is one that does not dissociate completely in solution. A typical example of a weak acid functional group is carboxylic acid (-COOH). In solution, compounds with a carboxylic moiety exist in an equilibrium, with some as -COOH (containing the hydrogen, also called “protonated”) and others as -COO^– and H⁺. In the dissociated form, the acid is more water soluble than in its protonated form due to the negative charge that makes it ionic.

Weak acids have a dissociation constant known as the pKa. When the solution is at the molecule’s pKa, the acid is 50% dissociated. When the solution has a lower pH than the pKa, there is less dissociation and the protonated forms of the molecule dominate. That has two important implications for herbicides.

the molecule becomes less water-soluble at lower pH
the molecule has fewer opportunities to interact with positively charged items

pH Dependent Solubility

Water-solubility is a two-edged sword. On the one hand, having a highly water soluble product makes it easier to dissolve in water. This pays dividends when mixing a batch or cleaning a sprayer because a product formulated as a solution will easily go into a true solution and will stay mixed. Examples are glyphosate, glufosinate, and salts of 2,4-D, MCPA, and dicamba.

On the other hand, most pesticides need to enter a plant to reach their site of action. And a plant cell, with its waxy cuticle and oily membranes, creates an effective barrier for water, and for water-loving molecules dissolved in it. As a result, a formulation that allows the water-soluble product to interact with an oily barrier is needed.

The products that can do this are surfactants. Acting like detergents, surfactants have regions in their structure that are oil-loving (lipophilic) and other regions that are water-loving (hydrophilic). Surfactants can therefore bind to both oil and water and provide a bridge for water-soluble products across oily barriers.

That’s also one of the reason that the most water-soluble products such as glyphosate and glufosinate contain a lot of surfactants in their formulation, reducing the concentration of active ingredient in the jug and possibly leading to foaming with agitation.

Pesticides have a wide range of solubilities, and for some, water pH will play an important role. Below is a table of some water solubilities of selected herbicides.

				Solubility (ppm)
Trade Name	Active Ingredient	Mode of Action Group	pH ~ 5	pH ~ 7	pH ~ 9
Select	clethodim	1	53	5,450	58,900
Ally 2	metsulfuron	2	550	2,800	313,000
Express	tribenuron	2	48	2,040	18,300
Pinnacle	thifensulfuron	2	223	2,240	8,830
Everest	flucarbazone	2	44,000	44,000	44,000
Simplicity	pyroxsulam	2	16	32,000	13,700
Frontline	florasulam	2	0.1	6	94
Varro	thiencarbazone	2	172	436	417
Raptor	imazamox	2	116,000	>626,000	>628,000
Pursuit	imazethapyr	2	2,570	12,870	7,500
2,4-D	2,4-D salt	4	29,934	44,558	43,134
dicamba	dicamba salt	4	>250,000	>250,000	>250,000
Roundup	glyphosate	9	>500,000	>500,000	>500,000
Liberty	glufosinate	10	>500,000	>500,000	>500,000
Heat	saflufenacil	14	30	2,100	>5000
Distinct	diflufenzopyr	19	63	5,900	10,550
Infinity	pyrasulfatole	27	4,200	69,100	49,000

Compare the solubility at pH 7 to that at pH 5. For most of these herbicides, water solubility is worse at lower pH. That is because they are more protonated and become more lipophilic.

I’ve placed a lot of Group 2 products in this table because those products are most often implicated in tank cleanout issues. All Group 2 products in this table, with the exception of Everest (flucarbazone-sodium) have lower solubility at pH 5 than they do at pH 7. For some, like pyroxsulam and floarsulam, it’s a big change. Those products, when acifified, are prime candidates for poor mixability and poor cleanout.

When it comes to dicamba, low pH has another side-effect. It makes the molecule more volatile, increasing danger to sensitive plants nearby. For that reason, acidification of dicamba in its Xtendimax and Engenia formulations is not permitted.

Note that the Group 4 examples, 2,4-D salt and dicamba salt, as well as glyphosate and glufosinate, are highly water-soluble and pH has very little effect on that.

Particularly for glyphosate, the claim that it becomes more oily at low pH and will therefore be taken up more easily, is not supported by these data. Considering that the most acidic pKa for glyphosate (it has four acidic groups) is 0.8, pH would need to be much lower for any noticeable impact on oilyness.

Tank Mixability

Given today’s environment of herbicide resistance, applications with multiple mode of action tank mixes are very common. Acidifying a spray mix to benefit one herbicide may create problems for its tank mix partners.

If there is a concern that spray water is too alkaline, it is recommended that the pH of the finished spray mix be measured. Since many herbicides are weak acids, they will lower the pH of the mixture by themselves. For example, the addition of glyphosate to water with pH 7.5 will drop the pH to about 5 or so, depending on the water’s buffering capacity.

As a result, glyphosate tank mix partners that are pH sensitive may suffer in the presence of glyphosate, and pH may actually need to be raised.

pH Dependent Half-life

Herbicides

There are a lot of claims that pesticides break down rapidly in alkaline spray water. And yet, in my career working primarily with herbicides, I do not recall this ever being a problem in practice.

Below is a table of herbicides for which I could find half-life information, with the help of this comprehensive list produced by Michigan State University.

Product	Active ingredient	Half Life
Atrazine	atrazine	More stable at high pH
Banvel	dicamba	Stable at pH 5 – 6
Bromoxynil	bromoxynil	pH 5 = 34 d; pH 9 = 1.7 d
Fusilade	fluazifop-p-butyl	pH 4.5 = 455 d; pH 9 = 17 d
Liberty	glufosinate-ammonium	Stable over wide range of pH
Gramoxone	paraquat	Not stable at pH above 7
Reglone	diquat	pH 5 = 178 d; pH 7 = 158 d; pH 9 = 34 d
MCPA	MCPA	pH 9 = < 5 days
Poast	sethoxydim	Stable at pH 4.0 to 10
Princep	simazine	pH 4.5 = 20 d; pH 5 = 96 d; pH 9 = 24 d
Prowl	pendimethalin	Stable over a wide range of pH values
Roundup	glyphosate	Stable over a wide range of pH values
Treflan	triflularin	Stable over a wide range of pH values
2,4-D	2,4-D	Stable at pH 4.5 to 7

Note that all of the herbicides are relatively stable. Some are a bit less stable at high pH, but none of the listed herbicides is in danger of breaking down on the day it is being applied. Only one is actually unstable at high pH – paraquat, a herbicide no longer registered in Canada and resticted in many other countries. Those with short half-lives experience them at quite high pH which are rarely seen in practice.

Insecticides

Insecticides are a different story. Several are very sensitive to pH. This table is again adapted from a comprehensive list published by Michigan State University, here.

Trade Name	Active Ingredient	Half-life
Admire	Imidacloprid	Greater than 31 days at pH 5 – 9
Agri-Mek	Avermectin	Stable at pH 5 – 9
Ambush	Permethrin	Stable at pH 6 – 8
Assail	acetamiprid	Unstable at pH below 4 and above 7
Avaunt	indoxacarb	Stable for 3 days at pH 5 – 10
Cygon/Lagon	dimethoate	pH 4 = 20 hrs; pH 6 = 12 hrs; pH 9 = 48 min
Cymbush	cypermethrin	pH 9 = 39 hours
Diazinon	phosphorothioate	pH 5 = 2 wks; pH 7 = 10 wks; pH 8 = 3 wks; pH 9 = 29 days
Dipel/Foray	b. thuringiensis	Unstable at pH above 8
Dylox	trichlorfon	pH 6 = 3.7 days; pH 7 = 6.5 hrs; pH 8 = 63 min
Endosulfan	endosulfan	70% loss after 7 days at pH 7.3 – 8
Furadan	carbofuran	pH 6 = 8 days; pH 9 = 78 hrs
Guthion	azinphos-methyl	pH 5 = 17 days; pH 7 = 10 days; pH 9 = 12 hrs
Kelthane	dicofol	pH 5 = 20 days; pH 7 = 5 days; pH 9 = 1hr
Lannate	methomyl	Stable at pH below 7
Lorsban	chlorpyrifos	pH 5 = 63 days; pH 7 = 35 days; pH 8 = 1.5 days
Malathion	dimethyl dithiophosphate	pH 6 = 8 days; pH 7 = 3 days; pH 8 = 19 hrs; pH 9 = 5 hrs
Matador	lambda-cyhalothrin	Stable at pH 5 – 9
Mavrik	tau-fluvalinate	pH 6 = 30 days; pH 9 = 1 – 2 days
Mitac	amitraz	pH 5 = 35 hrs; pH 7 = 15 hrs; pH 9 = 1.5 hrs
Omite	propargite	Effectiveness reduced at pH above 7
Orthene	acephate	pH 5 = 55 days; pH 7 = 17 days; pH 9 = 3 days
Pounce	permethrin	pH 5.7 to 7.7 is optimal
Pyramite	pyridaben	Stable at pH 4 – 9
Sevin XLR	carbaryl	pH 6 = 100 days; pH 7 = 24 days; pH 8 = 2.5 days; pH 9 = 1 day
SpinTor	spinosad	Stable at pH 5 – 7; pH 9 = 200 days
Thiodan	endosulfan	70% loss after 7 days at pH 7.3 to 8
Zolone	phosalone	Stable at pH 5 – 7; pH 9 = 9 days

Among insecticides, dimethoate, amitraz, and malathion stand out as breaking down rapidly in alkaline water. For these products in particular, it may be important to acifify the spray mix if there is any delay in spraying.

Recommendations

I’ve never been a fan of messing with solution pH unless recommended on the product label. Even when there is evidence that lower pH improves efficacy, consider the impact on tank mix partners.

We’ve seen improvements in solubility and tank cleranout of Group 2 products with raised pH, and ammonia is the most cost-effective way to achieve that. But again, following label recommendations is strongly recommended. The consequences of changes in pH, particularly acifification, can be very detrimental. To be safe, consider doing a jar test before committing to a whole tank to a pH adjustment.

April 2, 2026

How to Interpret a Water Quality Test Result
It’s common advice: Test your water before using it as a spray carrier. You dutifully sample the well or dugout and await lab results. And what comes back is a whole lot of numbers. How to make sense of it all?
Three examples of water test results conducted by labs in Canada
All three of these tests report a large number of properties and identify specific minerals and other solutes. Which ones are important in spraying? Here is the order in which I look at the numbers.
Conductivity: This property is usually expressed as micro Siemens per cm (µS/cm) and simply identifies how many ionic solutes are in a sample (watch for alternate units such as mS/cm and convert if necessary). It doesn’t differentiate between any minerals or other molecules, and therefore has limited information. But it does tell us if there is a large or small issue with water quality. If conductivity is below 500 µS/cm, the water is probably good for spraying. If the value is around 1000 to 2000, further investigation is necessary. Some water samples return conductivity of more than 10,000 µS/cm, and it’s important to identify which salts are causing that problem.
Note that Total Dissolved Solids (TDS) are often listed, and these are related to conductivity. A common way to get TDS is to multiply conductivity by 0.65. The conversion factor depends on which salts are dissolved but the bottom line is that TDS and conductivity are closely related.
Bicarbonate: Bicarbonates are HCO₃ and their concentration is measured in milligrams per Litre (mg/L), which is the same as parts per million (ppm). Bicarbonates can antagonize Group 1 modes of action and the common threshold is 500 ppm. Research at NDSU has shown that Urea -Ammonium-Nitrate (UAN or 28-0-0 liquid fertilizer) can reduce bicarbonate antagonism in some Group 1 herbicides.
Bicarbonates are negatively charged and are associated with a positive ion, often the hard water cations sodium (Na), calcium (Ca) or magnesium (Mg). As such, waters that are high in bicarbonates are often also hard.
Total Hardness (calculated): This is one of the important parameters. Hardness antagonizes most weak acid herbicides, most importantly glyphosate and g;ufosinate, and also ties up surfactants and emulsifiers which can result in problems with mixing and compatibility. Hardness is caused by metal cations, in order of strength these are iron (Fe⁺⁺), magnesium (Mg⁺⁺), calcium (Ca⁺⁺), sodium (Na⁺), and potassium (K⁺). Of these, Mg and Ca are typically most abundant, although some water is high in Na.
The Total Hardness (ppm) reported in water tests is done by taking the most common two cations, calcium and magnesium, and using this formula: 2.497*Ca + 4.118*Mg. Note that some tests report hardness in Grains per Gallon, in this case, multiply grains by 17.1 to get ppm.
While this calculation usually gives an accurate prediction of hardness, you may need to have a look at iron and sodium as well. Iron is less common, but some well waters are high in sodium or potassium. These minerals are not captured in the Total Hardness measurement. A water test low in Total Hardness may still be high in sodium, these are typically the samples with high conductivity.
The threshold for Total Hardness depends on the herbicide, its rate, and the water volume. The most common quoted values are 350 ppm for the lower rates of glyphosate (1/2 L/acre equivalent), and 700 ppm for the higher rates. Lower water volumes increase the concentration of herbicide, and reduce the impact of water hardness or bicabonates.
pH: This parameter is a bit over-rated because it is later affected by the herbicide and adjuvant dissolved in it. There is usually no concern with pH between 6 and 8, and water is rarely outside this range. It is best not to change the pH of water unless it is required on the label for mixing, because some products require low, and others require high pH for optimum solubility. Compatibility is an ever greater concern as our tank mix complexity increases.
Water Conditioners
The most common water conditioner is ammonium sulphate [AMS, (NH₄)₂ SO₄]. In its pure form (21-0-0-24), a concentration of 1% to 2% w/v (8 to 17 lbs AMS/100 US gallons of spray water) solves most hard water and bicarbonate issues. Be cautious of using too much AMS (>3%), when added at high concentrations to some herbicides it can burn crops.
Research has shown that AMS works in two ways: The sulphate ion binds with hard water cations, forming an insoluble precipitate that prevents the antagonistic cations from binding to, and inhibiting, the herbicide. The ammonium ion has been shown to improve cellular uptake by weak ion herbicides.
Some product labels call for UAN as an adjuvant. UAN contributes ammonium, but not sulphate ions. As a result, while it may improve herbicide performance, it does not remove antagonizing cations from the mixture.
Acids have been used to combat hard water. Most common herbicides are weak acids, and the acid constituent, usually a carboxilic acid, has a unique pKa. The pKa is the pH at which half the molecules are protonated (contain a hydrogen atom, resulting in an uncharged acid constituent) and the other half are not protonated (negatively charged). If the spray mixture has a pH below the pKa, the weak acid herbicides become protonated. This means the herbicide becomes less water-soluble, but also that it has less chance of interacting with a hard water cation. Acids that work in this way are less effective at ameliorating the effect of hard water than AMS.
A small group of acids that includes citric acid and sufphuric acid can sequester or bind with hard water cations. But they do not contribute the ammonium ion that assists in weak acid herbicide uptake.
If your water is questionable for spraying, there are four common choices:
- Select a different well or dugout
- If the problem is barbonates or hardness, treat water with a conditioner such as Ammonium Sulphate (AMS), available in pure form as 21-0-0-24. Some acids (citric, sulfuric) can form conjugate bases with hard water cations, removing them from solution. But the associated significant lowering of pH should be treated with an abundance of caution as it may affect solubility of some pesticides.
- Reduce water volumes or increase herbicide rates.
- Use a municipal treated water source or invest in a reverse-osmosis (RO) system. RO is neither cheap nor fast and requires additional investment in storage, and a way to deal with solute-enriched waste water. But it may be the best option for some.
An Ammonium Sulphate calculator, originally developed by Winfield United using data from NDSU, can be downloaded here:
AMS-Calculator-Sprayers101-1 Download
An excellent resource for adjuvant and water quality topics is this addendum in the North Dakota State University Guide to Weed Control.
Using good quality water lowers the likelihood of problems with mixing and overall performance and that pays significant dividends later.
April 1, 2026
Circulating Spray Mix Through a Tank-Rinse Nozzle Maintains Nematode Concentration
This article was co-written with Jennifer Llewellyn, former OMAFA Nursery Crop Specialist
With more and more bio-rational products on the market, crop protection methods may require reassessment. Certain products require exacting water quality, cannot tolerate residues, and have half-lives that are both time- and temperature-critical. We’ve been getting questions about sprayer compatibility with some of these new products, so it seemed like a good opportunity to recycle this article from 2013.
Many horticultural commodities, such as turfgrass and nursery crops, include the application of live nematodes as part of their annual IPM program. We performed preliminary research into the claim that a grower’s nematode applications were becoming less effective. In the course of the investigation it was discovered that the nematode concentration (i.e. dose) sampled from the spray nozzle was diminishing over the course of the application.
(A) Tank-rinse assembly mounted through tank lid with a flow-regulating valve. (B) Close up of tank-rinse nozzle.
After eliminating potential sinks in the sprayer’s plumbing (e.g. filters, strainers, etc.) it was hypothesized that the nematodes were adhering to the interior of the poly tank. If this was the case, the concentration would drop as the level of spray mix dropped. To test the hypothesis, we installed a tank-rinse nozzle to sparge the inner walls of the tank throughout the application and to re-suspend any stranded nematodes.
A high capacity roller pump (Pentair series 1700C) was installed to operate the tank-rinse nozzle (Pentair Proclean Tankwash) during spraying. It was installed through a bulkhead fitting in the tank fill lid. During testing it was discovered that the tank-rinse nozzle shunted too much flow and pressure to maintain flow to the spray gun. A valve was installed behind the tank-rinse nozzle to restrict flow to the point where it gently rinsed the inner walls of the tank, restoring flow and pressure to the spray gun.
(A) Installing a high-capacity roller pump. (B) Tank-rinse nozzle, with valve, installed through tank lid. (C) Control manifold installed to plumb the return, the tank-rinse nozzle, spray gun and boom. (D) The entire installed system.
(A) Nematodes, as-shipped, in a sponge. (B) Suspending nematodes for tank mixing.
(C) Counting nematodes. (D) Undiluted, healthy nematodes in a stock solution via microscope ocular.
The 200 L tank was inoculated with a stock solution containing 25 million nematodes (125 nematodes / ml). 20 L of the spray solution was sprayed into a bucket every 10 minutes, whereupon 1 L of spray solution was immediately removed and 1 ml volumes were sub-sampled for counting.
In the first trial, nematode counts continued over a period of 2 hours and viability dropped by ~40%. It was assumed the damage was caused by prolonged circulation through the roller pump. In subsequent trials, the sampling duration reduced to 10 minutes (more realistically reflecting the time it took the grower to apply 200 L in the field). The tank was rinsed and re-inoculated for each trial. 1 ml samples were drawn from the spray gun, which operated continuously, with and without the tank rinse nozzle in operation.
Univariate analysis confirmed data normality and a GLM procedure was conducted for analysis of variance. Results indicate that nematode concentration dropped by ~15% without tank-rinse with minimal nematode damage observed. With the tank-rinse nozzle engaged, the concentration still declined slightly, but significantly less (<5%) (see graph below).
Nematode concentration over time for each condition.
The results suggest that a tank-rinse system that sparges the tank walls preserves nematode concentration throughout an application and may lead to more efficacious applications.
Horticultural Crops Ontario, Ground Covers Unlimited, Pentair (Hypro) and Nemapro are gratefully acknowledged for making this research possible.
August 25, 2025
Closed Transfer for Airblast Sprayers – A Learning Process
As Canadian farmers begin to adopt closed transfer systems (CTS), growing pains are to be expected. Instructions for installation and use are primarily European and field-sprayer centric. We’ve seen precious little in the way of practical advice for incorporating CTS into airblast operations.
This is a “live” article which we’ll update periodically. We encourage readers to contact us and share their observations and experiences (and photos) so we can all learn from them. We’re happy to keep contributions anonymous if that’s preferred.
This article does not intentionally imply any brand preference. Our experience is limited at this point and we are using any information we have access to. As the article grows, so will the combinations of sprayer and CTS. Also, we are not recommending or endorsing any of the following approaches. It’s still unclear if modifying the sprayer is the purview of the manufacturer / dealer of the sprayer or the CTS. At this point, we suspect it’s likely the owner that accepts any responsibility.
Does it matter where the CTS is relative to the sprayer?
If the system is gravity-fed, the coupler, the fill line and the connection to the tank must be higher than the fill level in the tank. Liquid won’t flow uphill unless it’s pushed from behind (pressure) or pulled (suction or siphon). Be aware this means the entire fill line should be above the tank’s fill level; sags will prevent fluid transfer. If we’re observing best practices, the tank should be half-full of water before you start adding products.
If the coupler uses suction from the sprayer itself, or employs a pump, relative height won’t affect filling. In this case it is likely part of a separate transfer system (i.e. not permanently mounted on the sprayer). It might be simple, or part of a larger and more sophisticated affair, but in either case it should be level, stable, and easily accessed without the operator having to reach or squat. Two examples are pictured below.
Here, a CTS is mounted to a hand cart so it can be wheeled into place and then put away. The sprayer provides suction via venturi to pull in the chemistry and a simple garden hose supplies municipal carrier / rinse water. Note the cinder (concrete) block used to stabilize the unit. Simple and effective.
Here, a coupler is part of a larger tender system. Carrier / rinse water is pumped from an onboard tank, through the coupler, and then into the sprayer.
How do I plumb the CTS to the sprayer?
If the CTS is mounted directly on the airblast sprayer, it’s typically a smaller, gravity-fed coupler. The rinse / carrier water is often from an external source (e.g. water tank, tower, pond or municipal water), but there are cases where an onboard water source can be used.
Provide Agro has attached a gravity-feed coupler to the secondary tank hatch. This is above the fill line, sealed tightly, and it uses an onboard rinse / carrier water source. If considering cutting into a hatch, be aware of the filter basket or any onboard rinse system. Also, note that letting the lid flop open (or setting it aside) should not damage the coupler itself.
No matter the rinse / carrier water source, it should match the manufacturer’s prescribed pressure range (generally between 3 – 6 bar or 45 – 85 psi) and have an anti-backflow device. There is no such device in this photo.
Some have suggested cutting a hole in the tank itself, above the highest possible fill line, and sealing the coupler in place. This is not simple. If you find a flat horizontal surface and you are equipped to cut poly, Fiberglas or steel (listed in ascending order of difficulty), doing so could undermine tank integrity and create potential for leaks. We won’t even entertain what would happen to your sprayer warranty… assuming someone still has one.
If the intent is to couple a fill line to the sprayer, the best approach is to tee a fitting into the suction-side of the sprayer plumbing to draw product in through the pump. Consider accessibility and safety first: Can you safely and easily reach the suction side of the sprayer plumbing? Is the PTO shaft too close for comfort? Will anything stick out past the sprayer that might create a risk of snagging a crop canopy or trellis? If a tee can be plumbed in, will it need to be secured to the chassis in some way to create stability?
There is no easy or universal answer to these questions.
On this sprayer, the only easily-accessed point is between the suction filter and pump. Creating a tee that would accommodate a dry poppet fitting is challenging.
In the case of this 3-pt hitch sprayer, there is no simple way to access the suction side of the plumbing. Perhaps a tee could be added and the fitting extended up-and-out from under the chassis. Securing the fitting might require strapping it to the back of the tank, or to a mast of angle iron (or similar) attached to the chassis. Imagination required. Apply within.
As for the fitting, what style is best? A cam lever style fitting will work, but it will leak a volume of liquid when it’s detached. A quarter-turn valve will also be required on the sprayer, and preferably another on at the end of the feed line, so that’s two more valves in play when loading. And, for the sake of safety, best practice would to be to use a cam cap on the sprayer just in case the quarter-turn valve gets snagged and opens. Far safer and more efficient, a dry poppet style fitting will ensure minimal spillage when the hose is disconnected, with no additional valves or caps required.
Finally, what of the fill line itself? We’re seeking confirmation, but we have been told of a situation where the pump suction was sufficient to collapse the feed line. This is why some CTS manufacturers provide the hose and fitting with the units. At minimum, check the CTS manufacturer’s instructions and ensure the hose is rated for the degree of suction created by the pump.
Send us your experiences
And that’s all we have for now. We encourage you to reach out to us with your successes and failure and we’ll update this article for others to learn from.
Happy Spraying.
May 26, 2025