🌿 Determination of nitrate, nitrite and ammonium nitrogen (mineral nitrogen) in field-moist soil — 40 g of homogenized soil (aggregates < 5 mm) is shaken for 1 h with 200 ml KCl 1 mol/l at 20 ± 2 °C, the extract is centrifuged (about 3000 g, 10 min) and determined in automated segmented flow analysis systems: the sum of nitrate and nitrite after reduction on a Cd-Cu column, nitrite by reaction with sulfanilamide and N-(1-naphthyl)ethylenediamine dihydrochloride, ammonium by the salicylate method with dichloroisocyanurate and nitroprusside; moisture according to ISO 11465, PN-ISO 14256-2

Environment PN-ISO 14256-2

Overview

WHAT THE STANDARD COVERS. We read the text of the standard in the iTeh sample of ISO 14256-2:2005 (first edition, English text): contents, foreword, Clauses 1–6 and Clause 7 up to 7.1.2 (extraction procedure) — the sample ends on page 6. We do not read the determination of the sum of nitrate and nitrite (7.2), nitrite (7.3) and ammonium (7.4), the flow diagrams (Figures 1–3), calculation (8) or the test report (9); we know the titles from the contents.

ACCORDING TO THE TEXT OF ISO 14256-2:2005. The standard was prepared by ISO/TC 190 “Soil quality”, Subcommittee SC 3 “Chemical methods and soil characteristics”; the series has two parts: 1 — manual method, 2 — automated method with segmented flow analysis. Scope (1): automated determination of nitrate, nitrite and ammonium in a 1 mol/l KCl extract of field-moist soil samples; for all types of soil homogenized by suitable methods. References (2): ISO 3696:1987, ISO 11465 (dry matter and water content). Principle (3): homogenized soil is extracted with 1 mol/l KCl solution, and the inorganic nitrogen compounds in the extracts are determined by automated spectrophotometric methods; note: the method is based on segmented flow analysis systems, but continuous flow analysis systems may also be appropriate. Reagents (4): grade 2 water according to ISO 3696 (≤ 0,2 mS/m at 25 °C); ammonium chloride, potassium chloride, sodium citrate, sodium hydroxide, potassium nitrate, sodium nitrite, sodium salicylate, sulfanilamide, ammonium sulfate, sodium potassium tartrate, HCl 1 mol/l, H3PO4 85 %, N-(1-naphthyl)ethylenediamine dihydrochloride, sodium nitroprusside, sodium dichloroisocyanurate, wetting agent (polyoxyethylene lauryl ether 30 %, not longer than 6 months), coarse cadmium powder 0,3–0,8 mm; KCl 1 mol/l (74,55 g/l) and 2 mol/l (149,10 g/l); stock solutions: NH4-N 200 mg/l (0,9439 g ammonium sulfate in 1 l, in the refrigerator at least one month), NO3-N 375 mg/l (2,7083 g KNO3 in 1 l, at least six months), NO2-N 300 mg/l (1,479 g NaNO2 in 1 l, at least six months); nitroprusside solution (1 g/l), dichloroisocyanurate (2 g with 25 g NaOH in 1 l), buffer I (ammonium chloride, ammonia, wetting agent, pH 6–8), buffer II pH 5,2 (citrate and tartrate, HCl), Cd-Cu reducing agent (cadmium powder washed with HCl, then with CuSO4 solution 20 g/l, stored in the dark), colour reagent I (sodium salicylate 80 g and NaOH 25 g in 1 l) and II (H3PO4, NED 0,5 g, sulfanilamide 10 g in 1 l). Apparatus (5): balances 0,1 g and 0,001 g; 500 ml PE bottles neither absorbing nor releasing nitrite or ammonium; end-over-end shaker at 40 min⁻¹; centrifuge for 100 ml tubes; 100 ml conical flasks; three segmented flow systems — for the sum of nitrate and nitrite (with a reduction column), for nitrite and for ammonium — each with sampler, pump, analysis unit, photometer and recorder (flow diagrams in Figures 1–3, to be adapted); U-shaped Cu-Cd reduction tube, about 15 cm, internal diameter 2 mm. Sampling (6): samples are protected from warming during sampling and transport (cool box recommended, especially in late spring and summer); analysis within three days — storage at 4 °C, otherwise freezing at −20 °C (several weeks without significant change in mineral nitrogen); thawing at room temperature with homogenization and extraction within 4 h of the start of thawing, or at 4 °C for at most 48 h; the sample to be frozen should be as small as practicable and homogenized before freezing; laboratory sample — homogenization by hand (with rubber gloves) or mechanically to aggregates < 5 mm; moisture on part of the sample according to ISO 11465. Extraction (7.1): KCl 1 mol/l at a ratio of 1:5 at 20 ± 2 °C, because the amount of extractable ammonium nitrogen depends on temperature (in other climates another constant temperature may be chosen and stated in the report); centrifugation is preferred because most filter papers absorb ammonium or are contaminated; when filtering, filter papers are stored for at least a week in a desiccator over concentrated sulfuric acid and the first 20 ml of filtrate discarded; alternatively settling for 4 h at a temperature not above 4 °C; 40,0 g of sample, 200 ml KCl at 20 ± 2 °C, shaking 1 h, about 60 ml of suspension centrifuged for 10 min at about 3000 g; blank with KCl only; determination immediately, at the latest one day after extraction, or the extract stored at ≤ 4 °C for at most one week; note: with analysers having three units, nitrate, nitrite and ammonium standard solutions can be prepared together.

STATUS (as of 03.10.2026). In the PKN search (term “14256-2”, 03.10.2026) PN-ISO 14256-2:2010 (Polish version, “Introduces: ISO 14256-2:2005 [IDT]”) has no withdrawal note. Card: publication date 24.09.2010, 16 pages, KT 191 Soil Chemistry, ICS 13.080.10, no withdrawal note and no replaced standard. In the iTeh catalogue (read 03.10.2026) ISO 14256-2:2005 has the status “Published”, stage 90.93 (international standard confirmed), published 12.01.2005.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, load up to 17.09.2026, read 03.10.2026). The number 14256-2 appears in 7 records at 2 laboratories: AB 1095 (4), AB 313 (3). In the current PCA documents (read 03.10.2026; AB 1095 issue No. 25 of 03.07.2026, AB 313 issue No. 43 of 08.07.2026) the number appears at the same 2 laboratories — once in each document, in one reference document cell covering all forms of nitrogen (hence 7 records and 2 lines with the number); in each document the number of page markers equals the number of PDF pages, without repetitions; a search of all PCA documents downloaded from the BIP on 03.10.2026 found no laboratories outside the database copy. Form “PN-ISO 14256-2:2010” at both. In the database copy at AB 1095 the letter “M” is appended to the standard — in the PCA document it is a separate column with the location code (Mysłowice), not part of the designation. None of these items is suspended. The “Laboratories” tab (term “PN-ISO 14256-2”) shows both laboratories — checked by a tab query on the labcoda.pl production server on 03.10.2026.

WHAT THE LABORATORIES TEST (items in PCA). Both items: continuous flow analysis (CFA) with spectrophotometric detection. AB 313 (“Soil”): nitrite nitrogen (0,10–50,0) mg/kg, ammonium (15,0–500) mg/kg, nitrate (5,0–500) mg/kg. AB 1095 (“Soil (soil extract)”, Mysłowice location): ammonium nitrogen (0,50–500) mg/kg, nitrate (1,0–500) mg/kg, nitrite (0,10–20) mg/kg and mineral nitrogen by calculation.

WHERE AN APPARENTLY CORRECT RESULT IS EASY TO GET. With the sample: forms of mineral nitrogen change after sampling — samples must not warm up in transport; without freezing, analysis within three days at 4 °C; after thawing at room temperature, extraction within 4 h (6.1) — with samples stored longer the result may be analytically correct but invalid for the soil. With the state of the soil: the standard concerns field-moist soil, and the result is converted using moisture according to ISO 11465 (1, 6.2) — a sample dried before analysis does not give a result according to this standard. With extraction temperature: the amount of extracted ammonium nitrogen depends on temperature — 20 ± 2 °C or another constant temperature stated in the report (7.1.1). With separating the extract: filter papers absorb or introduce ammonium — centrifugation, and when filtering, filters dried over sulfuric acid and the first 20 ml discarded (7.1.1). With analysis time: extract immediately, at the latest the next day, or at ≤ 4 °C for at most a week (7.1.2). With the technique: the standard describes segmented flow systems and admits continuous flow analysis systems as possibly appropriate (3, note) — both PCA items state CFA. With nitrate: according to the contents the sum of nitrate and nitrite (7.2) and nitrite separately (7.3) are determined, and the result is expressed as nitrogen of nitrate plus nitrite (8.1) and nitrogen of nitrite (8.2) — the PCA items give nitrate nitrogen separately; how it was calculated is not visible from the items (procedure and formulae outside the sample).

WHAT WE DO NOT GIVE. We do not quote the operating conditions of the flow systems, calibration standards, checking of the reduction column efficiency, the formulae or the content of the test report — they lie outside the sample. We have not read ISO 14256-1 (manual method) or ISO 11465. We do not give fertilizer recommendations or limit values for mineral nitrogen.

Method principle

Field-moist soil, protected from warming and homogenized to aggregates < 5 mm, is shaken for 1 h with 1 mol/l potassium chloride solution (1:5) at 20 ± 2 °C and centrifuged. In the extract, automated segmented flow analysis systems determine spectrophotometrically the sum of nitrate and nitrite (after reduction on a Cd-Cu column and reaction with sulfanilamide and NED), nitrite alone and ammonium (by the salicylate method); the result is converted to the dry matter of the soil using the moisture according to ISO 11465.

Applications

• Nitrate, nitrite and ammonium nitrogen in field-moist soils of all types (1)
• Mineral nitrogen in soil — 7 items in the accreditation scopes of 2 laboratories in PCA

Key parameters

Standard

Standard number

PN-ISO 14256-2:2010

Title (PL)

Jakość gleby — Oznaczanie azotanów(V), azotanów(III) oraz jonów amonowych w glebach o wilgotności polowej z zastosowaniem ekstrakcji roztworem chlorku potasu — Część 2: Metoda automatyczna z zastosowaniem analizy przepływowej z segmentowaniem strumienia

Title (EN)

Soil quality — Determination of nitrate, nitrite and ammonium in field-moist soils by extraction with potassium chloride solution — Part 2: Automated method with segmented flow analysis

Step-by-step procedure

1. Sampling and transport

   No warming, cool box recommended; 4 °C up to 3 days or −20 °C (6.1). PN-ISO 14256-2:2010 without a withdrawal note in PKN (03.10.2026).

2. Laboratory sample

   Homogenization to aggregates < 5 mm; moisture according to ISO 11465 (6.2).

3. Extraction

   40,0 g + 200 ml KCl 1 mol/l, 1 h at 20 °C, centrifugation; blank (7.1).

4. Determination

   NO3+NO2 after Cd-Cu reduction, NO2, NH4 in the flow systems (7.2–7.4 — procedure outside the sample).

5. Result

   Conversion to soil dry matter; report with extraction temperature (7.1.1; 8–9 outside the sample).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Cadmium powder and Cd-Cu reducing agent (4.18, 4.30) — cadmium and its compounds are toxic
• Soil is mixed by hand only with rubber gloves (6.2)

Frequently asked questions