Spray Water Conditioning & Make Hard Water Behave
Sharpens glyphosate
Enter your water hardness, tank size and number of tanks to get the ammonium sulphate (AMS) dose in g/L, per tank and total kg — so hard water stops weakening glyphosate and your herbicide hits full strength.
Enter your spray water
Hard water — add AMS first, then the herbicide; aim for spray pH 5–6.5.
Next: dissolve 20 g/L of AMS (4 kg per tank) BEFORE adding the herbicide, then adjust pH to 5–6.5.
AMS dose scales with hardness; it also helps in cool weather. Not needed for all pesticides — check the label, and use a water test for the real hardness.
Spray water conditioning — key facts
- Problem
- Ca & Mg weaken weak-acid herbicides
- Fix
- Add AMS first to tie up those ions
- AMS dose
- ≈ 10 + hardness(ppm) ÷ 30 g/L
- Order
- AMS before the herbicide
- Target pH
- ≈ 5–6.5
- Best for
- Glyphosate & weak acids
- Hard water
- often >200 ppm (borehole)
- Privacy
- Runs in your browser; nothing uploaded
Don't let your water steal your herbicide
Hard water is a hidden cause of poor weed control. The calcium and magnesium that make water hard carry a positive charge, and weak-acid herbicides like glyphosate carry a negative one — so the two bond in the tank and the plant struggles to take the herbicide up. You see it as patchy kill and creeping resistance, when the real culprit was the water you mixed with. Adding ammonium sulphate first locks those ions away so the herbicide stays free and active.
This tool gives the AMS dose in g/L, the amount per tank, the total kilograms and a hardness class from your water hardness and tank setup. Use it to condition the water before every hard-water spray, add the AMS before the herbicide, and aim for a spray pH around 5–6.5. Pair it with the Herbicide Dose, Dilution Ratio and Knapsack Sprayer Calibration tools for an accurate, effective spray.
Restore full strength
AMS ties up Ca and Mg so glyphosate works.
Right dose, no waste
Match AMS to your measured hardness.
Get the order right
AMS first, then the herbicide — every time.
Better, even kill
Conditioned water lifts uptake and control.
Frequently Asked Questions
What is spray water conditioning?+
It's treating the water in your spray tank before you add the herbicide so the water doesn't reduce the herbicide's strength. The main problem is hardness — dissolved calcium and magnesium — which binds to weak-acid herbicides like glyphosate. Adding ammonium sulphate (AMS) first ties up those ions so the herbicide stays active.
How is the AMS dose calculated?+
A practical rule of thumb is AMS ≈ 10 + hardness(ppm) ÷ 30 grams per litre of spray water. For example water at 300 ppm hardness needs about 10 + 300 ÷ 30 = 20 g/L; multiply by tank litres for the per-tank amount, and by the number of tanks for the total kilograms.
Why does hard water weaken glyphosate?+
Hard water carries positively charged calcium and magnesium ions. Glyphosate and other weak-acid herbicides are negatively charged in solution, so they bond to those ions and form a salt the plant absorbs poorly. The result is reduced uptake and patchy control — especially at low spray volumes where the herbicide is concentrated.
Why add AMS before the herbicide?+
AMS must dissolve and grab the calcium and magnesium ions first, while they are still free in the water. If you add the herbicide first it bonds to those ions before the AMS can capture them, and the conditioning fails. Always fill, add and fully dissolve the AMS, then add the herbicide.
What spray pH should I aim for?+
Most weak-acid herbicides work best in slightly acidic water, around pH 5–6.5. Many waters are alkaline (pH 7.5–8.5), which speeds breakdown of sensitive actives. AMS lowers pH a little; for very alkaline water a separate acidifier may also help. Always check the product label for its preferred pH.
How do I know my water hardness?+
Test it with a hardness strip or kit, ask your water supplier, or send a sample to a lab — results come as ppm or mg/L of calcium carbonate. Borehole and groundwater are often hard (over 200 ppm); rainwater and many surface sources are soft. Hardness can change with the season, so re-check periodically.
Which herbicides benefit most from AMS?+
Weak-acid herbicides — glyphosate is the classic example, along with 2,4-D amine, glufosinate, sethoxydim and several others. Read the label: many recommend AMS in hard water. Some products already contain water conditioners, so check before adding more. Non-weak-acid products may not need it.
Can I use too much AMS?+
Adding far more than needed wastes money and can leave undissolved residue or, with some tank mixes, cause compatibility issues. Match the dose to your water hardness rather than guessing high. If you mix several products, jar-test first and follow the label order, adding AMS early in the fill.
Does this replace a label or jar test?+
No — it gives a sound starting dose for conditioning hard water with AMS, but the product label is the final authority on rates, water volumes and tank-mix order. For unfamiliar mixes, do a small jar test, and adjust for your measured hardness and water pH on the day.