Pasture nutrition splits on one question: are you grazing it or cutting it? Grazing returns most nutrients to the paddock in dung and urine. Cutting hay loads them onto a truck and drives them away. The same paddock needs a very different program depending on the answer.
What hay actually removes
This is the number that surprises people. Potassium removal in hay is heavy — far heavier than in grain, because you are exporting the whole plant rather than just the seed.
| Cutting | Roughly removes | To replace K2O you need |
|---|---|---|
| 1 t/ha of hay | ~20 kg K2O | ~40 kg/ha SOP, or ~33 kg/ha MOP |
| 4 t/ha | ~80 kg K2O | ~160 kg/ha SOP, or ~133 kg/ha MOP |
| 8 t/ha | ~160 kg K2O | ~320 kg/ha SOP, or ~266 kg/ha MOP |
Cut hay off the same paddock for several years without replacing potassium and it will run down, whatever the original soil test said. Removal figures vary with species and cutting stage — use your own test rather than these as a budget.
The nutrients that go first
Potassium
The one most often under-replaced on hay country, and it shows up as declining yield long before anyone tests for it. Sandy soils hold very little to begin with. Source depends on salinity and sensitivity — SOP where chloride is a problem, MOP where it is not.
Sulphur
Sulphate leaches like nitrate, so it runs down on sands and in wet years. Deficiency looks like nitrogen deficiency and gets misdiagnosed constantly. Ammonium sulphate supplies nitrogen and sulphur together; SOP supplies potassium and sulphur together.
Phosphorus
Drives root development and, in legume-based pasture, the clover — and the clover is what fixes your nitrogen. Under-fertilise phosphorus and you lose the legume, then you lose the free nitrogen with it. That is usually a more expensive mistake than the phosphorus would have been.
Nitrogen
The lever on bulk, especially for a planned cut or a feed gap. Urea 46-0-0 carries the most nitrogen per tonne, so you cart and spread least — but surface-applied urea on warm moist ground loses nitrogen to the air unless it is watered in or applied ahead of rain. See urea volatilisation and ammonium sulphate vs urea.
Grazing versus cutting
| Grazed pasture | Cut for hay or silage | |
|---|---|---|
| Nutrient export | Low — most returns as dung and urine | High — the whole plant leaves |
| Potassium | Usually maintenance | Replacement, every cut |
| Main risk | Uneven return — nutrients concentrate at camps and water | Steady run-down that is invisible until yield drops |
| Testing | Every 2–3 years | Annually |
If you cut hay, test annually. It is the cheapest part of the program and it is the only way to see the run-down coming.
Getting it quoted
Send the soil test, the area, and how much hay you are cutting per hectare — that last figure is what sets the potassium budget. Through soil test matching we will come back with the analyses that fit or a blend specification, plus a delivered price.
Send your soil test, the area and your cutting yield. We will match the analyses and quote the tonnage delivered.