Category: Spray Basics

  • Sprayer Loading and the Jar Test

    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.

    Note the undissolved residue collected on these swatches of red filter material. Products dissolve faster and better in higher carrier volumes.

    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 1950s 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:

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

    Adjuvants:

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

    1. Prepare: Read all labels for formulation details, water quality requirements (pH/hardness), and mixing order. Shake liquid containers to ensure consistency.
    2. Initial Carrier: Fill a 1-litre glass jar with 250 ml of water (or 375 ml if using oil/fertilizer).
    3. 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).
    4. 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.
    5. 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.
    6. 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.

    OrderIngredientQuantity for 500 ml or 500 g of product labeled for 1,000 L of final spray volume
    1Compatibility agents5 ml (1 teaspoon)
    2Water soluble packets, wettable powders and dry flowables. Include a 1cm2 cutting of PVA packaging.15 g (1 tablespoon)
    3Liquid drift retardants5 ml (1 teaspoon)
    4Liquid concentrates, micro-emulsions and suspension concentrates5 ml (1 teaspoon)
    5Emulsifiable concentrates5 ml (1 teaspoon)
    6Water-soluble concentrates or solutions5 ml (1 teaspoon)
    7Remaining adjuvants and surfactants5 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

  • Cleaning Your Sprayer

    Cleaning Your Sprayer

    We all know the importance of cleaning out a sprayer. It protects a sensitive crop. It protects people working with the sprayer. It protects the sprayer and its components. But cleaning the sprayer is a pain. Here are some tips to make it easier.

    Some herbicide label instructions are cumbersome, requiring many flushes with full tanks of water. Many applicators look for shortcuts and hope they get away with it. It doesn’t have to be guesswork. The following is a checklist that may help.

    Be Prepared

    A few supplies can help ensure a clean sprayer tank.

    • A defoaming agent saves water and time
    • A cleaning agent (commercial products, or simple household ammonia) is useful, and recommended, for Group 2 products except the imidazolinones.
    • A supply of clean water, preferably with its own pump, and a pressurized spray hose helps clean the sprayer inside and out.
    • A wash-down nozzle (whose flow requirements can be met by the clean water pump) can automate the tank wash-down.
    • A bucket and brush for rinsing screens is very useful.

    Products to Watch:

    The products most frequently implicated in sprayer contamination are two members of the Group 2 modes of action: the sulfonyl ureas (e.g., thifensulfuron (Refine) and tribenuron (Express)), and the triazolopyrimidines (e.g., florasulam (Frontline, PrePass) and pyroxsulam (Simplicity)). Since these herbicides dissolve better at higher pH, proper cleanout usually requires ammonia, a weak base that raises the solution pH. The third member of Group 2 products, the imidazolinones (imazethapyr (Pursuit), imazamox (Solo, Odyssey), imazamethabenz (Assert), imazamox (Ares,  Adrenalin, Altitude or Viper)), tend not be implicated in as many residue issues, and don’t require ammonia for cleanout.

    Be Prompt and Thorough

    Remove pesticide from mixing and spray equipment immediately after spraying – it makes the job easier. The main areas of concern are the tank wall, sump, plumbing (including boom ends), and filters. First, spray the tank completely empty while still in the field. It’s sometimes OK to cover previously sprayed areas – all herbicides must be crop-safe at twice the label rate to be registered by the PMRA. Take care with residual products that may create problems down the road. Reduce the rate or choose a fallow field to be certain. Second, add 10 x the sump’s remnant of clean water, circulate, ensuring agitation is on, and spray it out in the field as well. Repeat. These two rinsing steps will take care of the majority of the cleaning and won’t take very long. The less remaining volume there is in your tank after the pump draws air, the less water is needed to dilute this remainder to an acceptable concentration. Having a clean water tank on the sprayer and a wash-down nozzle makes this job easier.

    Visual Inspection

    Herbicide residue may precipitate out of solution in some parts of the sprayer or plumbing. A thorough visual inspection can identify these problem areas and ensure that they are cleaned properly.

    Tank Wall

    Removal of residues from tank walls is best accomplished with a direct, pressurized spray. Make sure all parts of the wall have been in contact with clean water. Use a wash-down nozzle if it provides complete and vigorous coverage of the interior tank surface.

    Sump

    Empty the sump as completely as possible by spraying it out. Any spray liquid or herbicide concentrate remaining in the sump area will be re-circulated in the sprayer. The only way to remove any remaining herbicide is through dilution by repeatedly adding water, and leaving as small a remainder as possible.

    Plumbing and Boom

    Plumbing can be a significant reservoir of herbicide residue. Removal from plumbing can be achieved by pumping clean water through the boom while ensuring that all return and agitation lines also receive clean water and all residue is flushed out. This may require opening and closing various valves several times, and repeating the process with new batches of clean water. Boom ends can extend up to 6” beyond the last nozzle at each end of each boom section. These ends must be flushed to removed trapped residue. A useful product that does this automatically is the Pentair Hypro Express Nozzle Body End Cap, or better yet, consider recirculating booms.

    Dilution

    The most effective use of a volume of rinse water is to divide it equally across several repeat washes. Assuming a 10 gallon sump remainder, three washes with 30 gal each are as effective as two washes with 70 gallons each, and equal a single 600 gal wash.

    It’s even more efficient to use a separate clean water pump, introducing clean water as the rinsate is sprayed out. This saves water and time, and results in even more dilution.

    Filters

    Nozzle screens and in-line filters can be a significant reservoir for undiluted or undissolved herbicide and are one of the most overlooked parts of sprayer decontamination. Remove all filters and nozzle screens and thoroughly clean these with fresh water. Run clean water through plumbing leading to the screens.

    Nozzle Bodies

    Nozzle bodies can harbour herbicide mixture. When cleaning a spray boom, rotate through all nozzles in a multiple body to ensure clean water reaches all parts of these assemblies. Remove screens that may have been used with herbicide.

    Tank Cleaning Adjuvants

    Adjuvants such as ammonia can assist the tank decontamination process, especially with sulfonyl urea and triazolopyrimidine-containing products. Ammonia does not neutralize herbicides, but it does raise the pH of the cleaning solution which helps sulfonyl urea herbicides dissolve. When decontaminating after an oily (EC) formulation, the use of a wetting agent such as AgSurf will assist in removing oily residue that may trap SU herbicide on tank and hose material. Commercial tank cleaning products that contain ingredients for removing persistent deposits are available.

    Tank and Boom Material

    Both plastic and stainless steel are common tank and wet boom materials, and both can be cleaned using the above procedures.  However, stainless steel is easier to clean, and this means that less time may be required. Consider the choice of materials a productivity factor in your next purchase or upgrade decision.

    Rinsate Disposal

    Always spray out the tank in the field. Do not drain the tank while stationary unless you are certain it is free of pesticide and that you are away from sensitive areas and waterways. Consider a continuous rinse system. Consider building a biobed for safe disposal of dilute pesticide waste.

    Sprayer cleanout will probably never be the easiest job on the farm. But looking at it in a smarter way can prevent frustration and save time.

  • Tank mixing Urease and Nitrification Inhibitors in Corn Weed-and-Feed Applications

    Tank mixing Urease and Nitrification Inhibitors in Corn Weed-and-Feed Applications

    This 2023 article is based on work performed by Mike Schryver, BASF Technical Service Specialist.

    Nitrogen is an essential nutrient required throughout a plant’s lifecycle. It is commonly applied to corn in either a granular form as urea or in a liquid form as urea-ammonium nitrate (UAN). Depending on soil type and precipitation, significant amounts of nitrogen can be lost to leaching, denitrification and volatilization as N2O (a greenhouse gas). Learn more about nitrogen in soil in this excellent overview by University of Minnesota Extension.

    With the 2020 announcement of Canada’s Strengthened Climate Plan, Ontario is committed to a 30% reduction of 2020 N2O emission levels by 2030. Adding urease and nitrification inhibitors (aka stabilizers) to nitrogen fertilizer applications is an environmentally sustainable practice that reduces nitrogen losses and improves yield.

    Another essential plant nutrient, Sulphur, is applied in liquid-form as ammonium thiosulphate (ATS). Primarily used to increase corn yields, high rates (approx. >10% by volume) of ATS can also inhibit urease and nitrification, albeit not as well as other nitrogen stabilizing options.

    In the pursuit of productivity, UAN and ATS are often combined to serve as an herbicide carrier in corn weed-and-feed applications. However, liquid fertilizers are dense solutions that contain charged ions and exhibit a reduced capacity for solubilizing pesticides. This complicates the tank mixing process. When micronutrients like sulfur are added to nitrogen-based formulations, physical incompatibilities can arise that cause uneven applications and can even clog sprayers.

    Given the known compatibility issues, questions have been raised about the best way to introduce urease and nitrification inhibitors to tank mixes of UAN, ATS and herbicide. Specifically:

    1. Stabilizer Compatibility: What is the impact of adding nitrogen stabilizers to UAN carriers containing leading corn herbicides formulated as emulsifiable concentrates (EC) or suspension concentrates (SC)?
    2. Mixing Order: When UAN and ATS are premixed, does their ratio, or the addition of nitrogen stabilizer affect tank mix compatibility with herbicides?

    To answer these questions, we performed a series of jar tests.

    Method

    300 ml jars with magnetic stir bars were mixed to reflect a 10 gpa application. UAN was chilled to approx. -5°C and herbicides were added at 2x the labelled rate to simulate a worse-case scenario. Nitrogen stabilizer was added at a ratio per manufacturer’s instructions. Products were introduced at 1 minute intervals to provide sufficient time for solubilization. Jars were left to rest for at least 1 hour after mixing, and then agitated to simulate interrupted spray jobs. The solution was then poured through a 100 mesh screen to simulate a worst case scenario for sprayers that typical employ 50 mesh filters.

    HerbicidesFertilizer carriersStabilizers
    Leading EC HerbicideUAN: 28%eNtrench NXTGEN (Corteva)
    Leading SC HerbicideATS: 12-0-0-26% SUAnvol (Koch)
    Tribune (Koch)
    Agrotain (Koch)
    Neon Surface (NexusBioAg)
    SylLock plus (Sylvite)
    Excelis Maxx (Timac)
    Table 1 Herbicides, carriers and stabilizers used in the study

    Results

    Stabilizer Compatibility

    EC herbicides have active ingredients that are soluble in water and include immiscible solvents. When added at 2x label rate to chilled UAN, followed by a stabilizer, agitation created an acceptable suspension (Figure 1). The EC separated to the top of the mixture following an hour rest but was easily reintegrated. There was no appreciable residue left behind when poured through a 100 mesh screen.

    Figure 1 UAN + EC Herbicide + Stabilizer after 1 hour rest. Image A is a control with no stabilizer and image B is the same control after agitation. The arrow indicates where ECs separate at the top of each jar. All products resuspended with agitation.

    SC herbicides have active ingredients that are water insoluble, but stable in an aqueous environment. When added at 2x label rate to chilled UAN, followed by a stabilizer, agitation created an acceptable suspension (Figure 2). The SC flocculated and formed a sediment at the bottom of the mixture following an hour rest but was easily reintegrated. There was no appreciable residue left behind when poured through a 100 mesh screen.

    Figure 2 UAN + SC Herbicide + Stabilizer after 1 hour rest. Image A is control with no stabilizer and image B is the same control after agitation. The arrow indicates where SCs settled, as depicted in the inset images showing the bottoms of each jar. All products resuspended with agitation.

    Best Practices

    • Contact manufacturers and conduct a jar test to confirm compatibility
    • Ensure thorough agitation (with or without a stabilizer, and especially after tank has settled)
    • Components may separate to the top (ECs) or settle on the bottom (SCs)

    Mixing Order

    Mixing order was tested using chilled UAN, ATS, and EC herbicide. It is well known that ATS should be added last in the tank mix order, and mixes that include a higher load of ATS relative to UAN exacerbate tank mix issues.

    This is seen in the following video where we combine 203 ml of chilled UAN, 30 ml of SC corn herbicide and 68 ml of ATS. On the left, UAN, then herbicide, then ATS mixes perfectly. However, when we start with UAN, then add ATS (which represents premixed fertilizer) then the herbicide does not suspend, and prolonged agitation does not improve the situation. The video is shown at 2x speed.

    We then added a nitrogen stabilizer to the series to see if it could correct the tank mix issue arising from adding ATS immediately after UAN. This replicates the situation an operator would face when purchasing UAN and ATS premixed. We also reduced the ratio of UAN to ATS from 3:1, to 5:1 to 8:1 to establish a threshold ratio that alleviated tank mix issues (Figure 3). All solutions were poured through 100 mesh screens to capture residue (Figure 4).

    Figure 3 SC Herbicide and stabilizer added to UAN and ATS premixed at different ratios. Agitated after 1 hour and poured through 100 mesh screens (inset images).
    Figure 4 Pouring EC jar test solutions through 100 mesh screens

    Best Practices

    • Contact manufacturers and conduct a jar test to confirm compatibility
    • ATS must be added after the herbicide (EC or SC). The stabilizer can be added last, but preferably ATS is the last ingredient in the tank.
    • Adding stabilizer will not reverse a tank mix error arising from adding ATS prior to the herbicide.
    • The higher the concentration of ATS, the higher the risk of incompatibility. A 5:1 ratio of UAN to ATS failed while a ratio of 8:1 succeeded. The threshold is likely 7:1.
  • How to Interpret a Water Quality Test Result

    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-Sprayers101-1Download

    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.

  • Drone Tendering – Considerations before Buying or Building

    Drone Tendering – Considerations before Buying or Building

    Much of this article is based on a session and tradeshow I attended at the 2026 Drone End-User Conference in Kansas City. I want to acknowledge the insightful information provided by the three session speakers, as well as the ~200 audience members that asked honest questions and shared their experiences. The speakers were Mr. Chase Plumer (Owner, ProBuilt Fabrication/ProDrone Spraying & Seeding, Seymour, IN), Mr. Klaytin Hunsinger (Owner, Hunsinger Ag Solutions, Rossville, IL) and Mr. Kyle Albertson (Owner, Albertson Drone Service LLC, Benton County IN).

    Tendering systems

    Drone-based crop protection is a rapidly growing industry and operator experience spans from novice to veteran. It follows that tendering systems are not a one-size-fits-all proposition. The best fit will be a configuration that is budget-conscious, reflects the size and nature of the operation, and accounts for future needs.

    We can categorize them by their complexity, cost and capacity.

    Entry-level tendering system: A starting point

    For those just getting started, focus on affordability (lower initial investment) and simplicity (basic components). Examples include skid or truck builds, which are removeable or permanent systems that either rest on a vehicle bed or are built on-and-around the vehicle. This is an operator-friendly system that is small and portable for easy access to diverse fields. It’s the least durable configuration, and not particularly efficient or upgradeable, but it will serve until you know what you really need and how you like to work.

    Mid-level tender system: Second year

    By year two, you might want a larger and more efficient configuration with additional storage and a few creature comforts to reduce operator fatigue. A truck build might suit, but this is more likely a trailed system that is still capable of being towed by a mid-sized (1/2 to 3/4 tonne) truck. Some operators feel enclosing the trailer reduces efficiency, while others appreciate the security and protection afforded by defined spaces.

    A mid level system has some capacity for modification, but isn’t designed to support multiple drones, and likely won’t have enough capacity to store a day’s worth of water, chemical, or fuel. The operator may wish to detach the truck to run for supplies. Or perhaps it makes more sense to run a truck with a skid-mounted tender system that trails a second, mid-level system to divide-and-conquer, or scale up for larger projects.

    Beware going too big, too quickly. A 30-foot gooseneck can get caught on hilly terrain, where a 20-foot flat bed with a straight truck might be better suited. Small to mid-size trailers also take less time to set up and tear down. Consider performing site recon before dispatching a mid-level tender system. This is an additional step, but it allows the operator to scope out potential hazards and is ultimately more productive because it prevents tender systems getting stuck or placed in inefficient or unsafe locations. For example, if a client is “plant-out, pick-in”, the fields are hard to service because there’s no way to access them with large vehicles. Pilots become landscapers, spending valuable time clearing an operations area.

    High-level tender system: Large scale and Commercial interests

    Made for efficiency, the limiting factor of this system is the drone’s productivity. This category is comprised of the largest gooseneck trailers, which may include an upper deck and enclosed areas. It has the highest capacity for water storage, can service multiple drones and has ample storage. Intended for large fields, the size of this unit can make it physically incapable of reaching smaller fields. While a one tonne truck might be able to tow it, an even larger vehicle might be more suitable. It may also be prohibitively inefficient given the time required for setup and teardown. Consider an operator that requires a 15 minute start-up and a 15 minute teardown to spray 250 acres at 50 ac/hr; At $20/ac, that’s roughly $500.00.

    Phiber’s DASH Carrier (image from website)

    Components

    Fundamentally, each tendering system has the same function, so they share the same basic components. Here’s an overview of common features and considerations.

    Trailer

    The trailer is (literally) the foundation of most tendering systems. Operators suggest building for your current budget but planning for future needs as best you can. Trailer size should reflect the nature of the farms you will be servicing and how best to access them. You should also consider the safest and most efficient workflow on and around the trailer before committing to a layout.

    Option 1 – Utility trailer

    AdvantagesDisadvantages
    Easy to get on/offLow ground clearance
    Less expensiveNarrow footprint for accessories (e.g. conventional tanks not fitting between wheel wells)
    Versatile (use for drones on season, and other tasks off season)Narrow if planning a top flight deck
    May be an insufficient trailer GVWR (Gross Vehicle Weight Rating). This is the maximum allowable total weight of a trailer when fully loaded.

    Option 2 – Flatbed gooseneck trailer

    AdvantagesDisadvantages
    More room for accessoriesMuch heavier. ¾ tonne truck likely not sufficient.
    Better ground clearanceHard to get into tight places (length dependent).
    Higher GVWRSet up / Tear down takes longer
    Potential for top flight deck. Typically, 102” wide, so top deck can be about the same.

    Option 3 – Enclosed trailer

    AdvantagesDisadvantages
    Protection from weather and elementsLimited clearance for large drones (e.g. 24’ long, 8.5’ wide)
    Increased security for equipmentHighest GVWR
    Could serve as mobile workspace / officeMost expensive
    Cleaner environment for charging batteries, and generators don’t need maintenance (e.g. filters changed) as often.Can get hot inside, both for people and battery overheating. Airflow on batteries is a necessity, and fans can only cool to ambient. Drone hasn’t got time to cool between fields.

    Vehicle

    Based on operator discussion, it seems many have a tendency to push their trucks to the limit… or beyond it. One operator uses a ¾ tonne truck to pull a 22-foot trailer with an upper deck. Another uses a 1 tonne (aka tonner) gas F350 which struggles to pull a 30-foot trailer. Others recommended the use of a single axle semi (e.g. a Kodiac or a Kenworth T300), which even used still has ample life left in it, and at ~15 to 17,000.00 USD is cheaper than buying a truck.

    Consider that if you run a two-person operation, you may want more than one vehicle. A smaller truck can be employed to run for parts or fuel, or as previously noted can be fitted with a skid mount and a 1,300 gal. poly tank to split up the duty.

    Tanks

    Tank size(s) will depend on how you choose to operate, how many acres you plan to do in a day, and the weight capacity of your truck and trailer. Again, there is no one solution, so consider the following scenarios before you commit.

    If you plan to hot load, perhaps you’ll just mix in a single, large tank. However, if you plan to switch between insecticides, fungicides and herbicides, one or two 100-gallon cone-bottom tanks with wash-down nozzles might make more sense. Then, you can carry clean water separately in a few repurposed IBC’s or go for the efficiency of a single, high-volume poly or stainless tank. Consider the most flexible and efficient arrangement.

    Will you have access to water, will you have water tendered, or will you carry enough for the day? Will you fill from a 3-inch connector or suffer the lost time and fill with a garden hose? Will your truck and your trailer handle that weight, and will the vessel(s) fit between the wheel wells? Are the tanks black or shaded to prevent algae and do you have a plan to baffle the volume, so it doesn’t slosh when you drive over uneven terrain? Larger poly tanks (e.g. ~1,000-gallon tanks) have spots molded in to accept baffles, but some operators noted it’s difficult to install them after-market. Slosh suppressors such as floating balls or lengths of poly French drain can help.

    Pumps and Lines

    While some prefab trailers offer pneumatic pumps, most must choose between electric and gas pumps, and there are pros and cons to both.

    Electric PumpGas Pump
    Low noiseHigh noise
    No exhaustExhaust
    Taxes the generatorDoes not tax the generator
    No fuelRequires fuel
    Low maintenanceRegular maintance
    May limit head pressureAmple head pressure

    Gas-powered pumps (e.g. Drummond or Predator transfer pumps) are relatively cheap, but some claim they have a high failure rate. This not only incurs downtime, but operators must deal with the chemical in the pump and lines during repair.

    Electric may be a better choice, if only to avoid the noise and exhaust, and some operators run them continuously to recirculate chemistry when not filling a drone. Consider the horsepower, gallons per hour and head pressure, especially if you are pushing flow to an upper flight deck.

    An AMT electric transfer pump on a mid-level tender system.

    You should be able to fill a drone in about a minute. Some operators have begun increasing fill line diameter from 1-inch to 1.5-inch but feel 2-inch lines are too heavy to warrant the few seconds saved during filling. This may not be a limitation, however, if they are part of a top flight deck arrangement, and not dragged along the ground.

    The auto shutoff function of a fuel-pump-style filler is preferred over a quarter-turn-style. The former contributes to foaming but some operators say that can be mitigated by using an anti-foam adjuvant and it’s less likely to create an overflow situation.

    Perhaps a metered flow valve that shuts off once a predesignated volume has been dispensed would be a workable solution. This would preserve speed, but without foaming or potential overflows.

    A loose line terminating in a quarter-turn valve fills quickly and with few bubbles, but is ultimately not ideal. It’s prone to causing overflows which increase the potential for operator exposure and cause point source contamination.
    A reeled hose and a fuel-pump style filler is a better approach. The hose can be recoiled to keep it from being underfoot, and the filler has a back pressure valve that shuts off when the drone is full. There is greater potential for foaming, but some suggest anti-foam adjuvants can help.

    Generator

    This proved to be a controversial subject at the conference. Many operators were unwilling to promote a single make or model, but the discussion resulted in some general guidance based on personal experiences. Generators will have a peak and a continuous performance rating. Ensure the sum total of all your draws does net exceed the continuous rating.

    Drones are getting bigger, and the number of electrically powered devices on the trailer is increasing. Smaller operations tend to employ mobile gas generators that produce less than 10 kW. Larger operations reported using 30 kW (or more) diesel standby generators to charge two drones, plus accessories, while ensuring room for future growth.

    A mobile gas generator (inverter or not) tends to be the cheaper, lighter alternative, depending on the wattage. They are a good choice for entry level systems and with regular maintenance will last longer, but are still a short-term proposition. Diesel generators tend to be more expensive, but are quieter, more fuel efficient and more reliable. A liquid propane standby generator is yet another option; Generally cheaper than diesel, consideration must be given to the weight and size of what is typically a 250-gallon propane tank.

    A few points raised by operators during the discussion:

    • Most standby generators do not need diesel emission fluid, while mobile generators do.
    • Many operators prefer the durability of mobile generators over standby generators. The former is built to be moved while the later presents issues with brackets, mounts and stators.
    • Warranties are advisable for inversion generators, as they are not easily repaired.
    • Standby gas generators (10 kW continuous / 13 kW surge) may require you to downrate the battery charger, or the heat can trip the breakers. It is not advisable to bypass breakers.

    Storage

    Storage is often overlooked but can be critical to efficiency. For example, if you plan to spray six, 50-acre farms in a day and it takes 10 minutes for set up and 10 for tear down, that’s two hours gone. Consider what you’ll need and where you’ll need it, and place storage accordingly to minimize downtime. PPE should be located near your flight deck or filling area. You’ll also want to consider carrying spare parts, such as an electronic speed controller, motor, pump and a full set or rotors.

    Batteries

    Some battery chargers feature water baths, misters or air conditioning, but at bare minimum batteries should charge in the shade and in a ventilated area (e.g. not enclosed in a storage or tool box). One operator vented air from a commercial blower fan to the batteries on the top flight deck.

    Connectivity

    A hotspot on your cellphone doesn’t always provide reliable service. Satellite internet providers such as Starlink or Xplore (depending on your location) might be a solution. If the controller drops a direct signal to drone, it can bridge to satellite to connect to the SIM card in most drones. Operators that use this system advise it’s best to rent the hardware (if possible) so if something damages it, you get a free replacement. 100 gb of monthly roaming has proven more than enough for most operators.

    Mounting solutions vary, but operators noted good experiences with companies such as Veritas Vans, which have a replacement policy. They warn against 3D printed options that tend to be produced using unsuitable filament materials. Operators that use magnetic mounts on their trucks have reported no issues. Some run wire through rear window or sliding door, and others pull the headliner down and run the power cord out through the third brake light.

    Operator safety

    Lastly but certainly not least, when it comes to the cost-benefit assessment of tender features, safety should always be a priority. Even simple comforts such as folding chairs combat operator fatigue, increase safety and happily also improve overall productivity. We’re none of us getting any younger.

    RV awnings, umbrellas, foldable Bimini-style tops or flip-up doors provide shade. Switching to lower-decibel equipment (e.g. inverter gas generators run at about 90 decibels and electric pumps are even quieter), enclosing loud systems, or positioning them far from the filling area, reduce noise and emission exposure. Chemical drift and exposure during filling should be considered, and PPE should be used and stored in convenient locations.

    Trailers that feature an upper flight deck sometimes include a central cable to tether belt harnesses. Stationary railings can help prevent falls, while a fold-up version provides clearance when backing the trailer into a shed.

    The drones themselves are a hazard. Long flight decks keep landings and lift-offs at a safe distance, and a protected cockpit area improves matters. Decks with pull-out platforms or hydraulic wings can increase the operating area and can be adjusted to account for adjacent roads and the slope of the ground. A short rail around the landing area can prevent a drone from slipping off; A falling drone is expensive, but falling or sliding into an operator is a disaster. The simplest approach might be to operate on the ground.

    An enclosed area for operators on a two-platform gooseneck trailer.
    Kodiak’s retractable flight deck on their skid-mounted system

    Take home

    The speakers left the session with some summary advice.

    • Trailer first, equipment second.
    • Build for today and tomorrow.
    • Function over form (stability, balance and access over appearance, bearing in mind that if it is a business, it can’t look terrible, either).
    • Efficiency from day one. Run a stopwatch (when the crew isn’t watching). Find and change the limiting factor, if it’s changeable. The right trailer improves efficiency even before the first acre is sprayed.

    Thanks to the many speakers, attendees and trades people that contributed to this article. If you want to share pictures and specs for your tender system, let us know! If we get enough interest we’ll publish an article showcasing your tender systems so others can learn from your experience.