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(Reaffirmed 2015)

IS ( 14684:1999
Reaffirmed 2005 )

(Reaffirmed 2014)
(Reaffirmed 2019)

(Reaffirmed 2013)

Indian Standard (Reaffirmed 2012)

DETERMINATION OF NITROGEN AND NITROGENOUS

COMPOUNDS IN SOILS (Reaffirmed 2011)

(Reaffirmed 2010)
ICS 65.080

(Reaffirmed 2009)

(Reaffirmed 2008)

(Reaffirmed 2007)

(Reaffirmed 2006)

(Reaffirmed 2005)

@ BIS 1999

BUREAU OF INDIAN STANDARDS

MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG
NEW DELHI 110002

April 1999 Price Group 1

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Soil Quality and Improvement Sectional Committee, FAD 27

FOREWORD

This Indian Standard was adopted by the Bureau of Indian Standards, after the draft finalized by the Soil
Quality and Improvement Sectional Committee had been approved by the Food and Agriculture Division Council.

Nitrogen is one of.the most essential nutrients required for successful crop production. It promotes vegetative
growth of the plants. Several Indian soils are deficient in nitrogen content and no standard method is available
for testing of nitrogen in soils. Hence, need was felt to provide appropriate analytical procedure for determination
of nitrogen and nitrogenous compounds in soils. This standard may help various research organizations and
those engaged in organized farming including plantation and forestry crops.

In reporting the result of a test made in accordance with the standard, if the final value, observed or calculated,
is to be rounded off, it shall be done in accordance with IS 2 : 1960 ‘Rules for rounding off numerical values
(revised)’.
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IS 14684:1999

Indian Standard
DETERMINATION OF NITROGEN AND NITROGENOUS
COMPOUNDS IN SOILS

1 SCOPE 3.2.6 Boric Acid

This standrd prescribes the methods for the 2 percent (m/v) aqueous solution containing 5 ml of
determination of total nitrogen and nitrogen mixed indicator solution per litre. The pH of the
compounds in soils. solution shall be adjusted to 5.0,

3.2.7 Standard Sulphuric Acid Solution, 0.1 N.

2 REFERENCES
3.2.8 Salicylic Acid: Sulphuric Acid Mixture
The Indian Standard listed below contains provisions
which through reference in this text, constitutes Dissolve 25 g salicylic acid in one litre of concentrated
provision of this standard. At the time of publication, sulphuric acid.
the edition indicated was valid. All standards are 3.2.9 Sodium Thiosulphate (Na,S,O,, 5H20),
subject to revision and parties to agreements based on Analytical reagent grade.
this standard are encouraged to investigate the
3.2.10 Potassium Chloride Solution (IN)
possibility of applying the most recent edition of the
standard indicated below: Dissolve 74.5 g potassium chloride analytical reagent
grade, in one litre distilled water.
IS No. Title
1070:1992 Reagent grade water (third revision) 3.2.11 Magnesium Oxide — Analytical reagent grade
(Heavy grade).
3 DETERMINATION OF NITROGEN IN SOIL
3.2.12 Devarda’s Alloy
(EXCLUDING NITRATE)
It is a mixture of Copper 50 percent (m/m), Aluminium
3.1 Apparatus 45 percent (m/m) and Zinc 5 percent (m/m) and is
available commercially (Lab grade or Reagent grade).
3.1.1 Macro-Kjeldahl Digestion Flask, 500 or 800 ml.

3.1.2 Macro -Kjedahl Digestion Unit 3.3 General

The Kjeldahl procedure is generally employed for

3.1.3 Macro-Kjeldahl Distillation Apparatus
determination of total nitrogen and Kjeldahl’s wet
3.1.4 Vacuum Pump digestion distillation procedure for determination of
total nitrogen involves two steps, namely:
3.1.5 Mechanical Shakei-
a) Digestion — Heating the sample with sul-
3.1.6 Hot Air Oven
phuric acid containing potassium sulphate,
and copper sulphate as catalyst, thus oxidis-
3.2 Reagents
ing the organic matter and converting
3.2.1 Sulphuric Acid, Concentrated. organic nitrogen into ammonium nitrogen;
and
3.2.2 Potassium Sulphate, Analytical reagent grade.
b) Distillation — Distilling the digest with
3.2.3 Copper Sulphate (CUS0,5H10), Analytical
excess of above 40 percent solution of sodium
reagent grade. hydroxide to recover ammonia in excess of
3.2.4 Sodium Hydroxide Solution standard boric acid which is thereafter titrated
against standard acid.
40 percent (m/v) solution in reagent grade water, kept
in a tightly stoppered pyrex glass bottle. 3.3.1 Procedure

Take 10 g of dry soil sample passed through 2 mm

3.2.5 Mixed Indicator Solution
sieve into a 500 ml or 1000 ml Kjeldahl flask and
Dissolve 0.5 g bromocresol green and 0.1 g methyl add 10 g of digestion mixture comprising of potassium
red in 95 percent (m/v) methanol. sulphate: copper sulphate 10:1 or 10.5; (m/m). Add

1
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IS 14684:1999

30 ml (6 ml/g of organic matter in soil) of concentrated 5 DETERMINATION OF AMMONICAL,

sulphuric acid and heat the flask continuously avoiding NITRITE AND NITRATE NITROGEN IN SOIL
excessive frothing by controlling heat. Raise the EXTRACTS
temperature to about 380”C and digest till the contents
of the flask are clear. Continue digestion for about 5.1 General
15 min and after complete digestion allow the flask Ammonical nitrogen in solutions containing
to cool and add 100 ml reagent grade water. glutamine or other alkali labile organic nitrogen
To determine ammonical nitrogen liberated by compounds may be estimated quantitatively from the
digestion, place a 500 ml Erlenmeyer flask containing ammonical nitrogen liberated by distillation of these
50 ml of boric acid under the condenser of distillation solutions with a small amount of magnesium oxide
apparatus so that the end of the condenser is below and determining ammonical nitrogen titrimetrically.
the surface of the boric acid. Hold the distillation The solution is then cooled, powdered Devarda’s alloy
flask. Cool, dilute and digest at 45° angle. Add glass is added and redistilled to recover ammonical nitrogen
beads and pour about 150 ml of sodium hydroxide formed as a result of reduction of nitrite and nitrate
solution (see 3.2.4), down the neck of the flask so that forms of nitrogen.
the alkali reaches the bottom of the flask without
5.2 Procedure
mixing appreciably with the digest. Attach the flask
quickly to the distillation apparatus, mix the contents 5.2.1 Extraction of Inorganic Nitrogen from Soils
throughly by gentle swirling and heat. Control the
Take about 50 g of fresh, wet soil sample in an
heating to prevent sucking by back of boric acid and
Erlenrneyer flask, add 250 ml IN acidified potassium
to minimize frothing during distillation. Check the
chloride solution, stopper the flask and shake on a
flow of cold water through the condenser is sufficient
mechanical shaker for one hour. Filter the contents
to keep the temperature of the distillate less than 35”C.
of the flask using a v~cuum pump or using a funnel
Collect about 150 ml of distillate, rinse the condenser
and Whatman N’o.1 filter paper or equivalent.
with water and stop distillation. Determine total
ammonical nitrogen in the distillate by titration with Transfer the filtrate to a 1000 ml Kjeldahl digestion flask
standard sulphuric acid. The colour change at end and add about 2 to 4 g magnesium oxide carefilly. Place
point of titration is from green to pink. a 250 ml Erlenmcyer flask containing 20 ml of 2 percent
boric acid (see 3.2.6) indicator solution under the
3.3.2 Calculation
condenser, the tip being placed below the boric acid level
Calculate total nitrogen in ammonical form, percent in the flask. Connect the Kjeldahl flask to the condenser
by mass of soil taken for the test by using the following and distill by heating. Collect about 40 to 45 ml of
formula: distillate, and stop distillation, Titrate the ammonia
against standard su!phuric acid. 1 ml of O.02 N standard
1 ml of 0.1 N standard sulphuric acid== 0.0014 g of
sulphuric acid is equivalent to 0.00028 g of nitrogen.
nitrogen.
5.2.2 Detwnin[]i[t )11<!f”ilrdrite and Nitrate Nitrogen
4 ESTIMATION OF TOTAL NITROGEN
INCLUDING NITRATE FORM Cool the flask after distillation (see 5.2) carefully add
1 to 2 g of powdmcd Devarda’s alloy and immediately
Take 10 g of soil sample in a Kjeldahl flask, add 35 ml connect the flask to the condenser. Distill ammonia by
of salicylic acid sulphuric acid mixture (see 3.2.7 heating the flask as described in (see 5.2). Titrate the
and 3.2.8) and mix well. allow the mixture to stand ammonia against \tu:ldard sulphuric acid. 1 ml of
overnight, add 5 g of sodium thiosulphate (see 3.2.9) 0.02 N standard .wid is equivalent to 0.00028 g of
and heat the flask till frothing subsides. Cool the flask, nitrogen.
add 10 g of digestion mixture comprising of potassium
NOTE --- To tictwmine ammonical, nitrite and nitrate forms of
sulphate: copper sulphate (see 3.2.2 and 3.2.3) 10:1
nitrogen, fresh ond moist sample is used. Determine the moisture
or 10 : 0.5 (rn/rn) and complete the digestion. content of
the soil by drying a suitable aliquot in an air-oven at
Determine ammonical nitrogen including nitrate by 105°C for 6 hours. Cool, weigh and calculate moisture content,
distillation as described in 3,3.1 and 3.3.2. percent by moss. Correct the result of inorganic nitrogen content
by compensating Ibr tile nmislure.
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Bureau of Indian Standards

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Review of Indiim Standards

Amendments are issued to standards as the need arises on the basis of comments. Standards are also reviewed
periodiedly; a standard along with amendmen~ is reaffirmed when such review indicates that no changes are
needed; if the review indicates that changes are needed, it is taken up for revision. Users of Indian Standards
should ascertain that they are in possession of the latest amendmen~ or edition by referring to the latest issue
of ‘BIS Handbook’ and ‘Sk~ndards Monthly Additions’
This Indian Standard has been developed from DOC:No. FAD 27 (792).

Amendments Issued Since Publication

Amend No. Date of Issue Text Affec~

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