Do two water sources at the same pH require equal acid additions?

Initial pH does not establish buffering capacity. Phosphoric acid also adds phosphorus to the nutrient balance.

Compare acid demand to the same endpoint

Obtain alkalinity data for both waters. Have qualified personnel measure acid consumption to a common endpoint under an appropriate procedure. Include acid concentration and phosphorus contribution separately in the fertigation formulation.

Will phosphoric acid change the existing fertiliser programme?

Include phosphorus from acidification in the full nutrient budget and recheck target concentrations. Irrigation water acidification review: Have qualified personnel generate a titration curve using representative raw water and calculate the phosphorus introduced. Phosphorus source selection: At actual stock concentration, check compatibility with calcium salts. Measure precipitate and screen loading.

Checking Phosphoric acid assay and Phosphorus nutrient content

Phosphoric acid assay (% by mass or titratable equivalents): State the acid equivalent, whether total or free acid is measured, the as-received or dry basis, and the analytical endpoint. Phosphorus nutrient content (% by mass): Identify water-soluble or total P₂O₅ and the analytical basis. Convert elemental P before comparing. Specified impurities (mg/kg): For the intended use and market, list each element, method and quantification limit. Request results for the stated batch.

What to record

  • Water source
  • Initial pH
  • Alkalinity
  • Acid consumption basis
  • Phosphorus introduced

Technical references

Products and processes

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