0.09 gram. Nitrogen in sprinkling water, 0.000048 gram.
_Nitrogen in Exhaled Products._—
FIRST PERIOD. SPRINKLING.
Ammoniacal nitrogen collected in the dilute sulfuric 0.00012 gram.
acid
Ammoniacal nitrogen collected in the condensation waters 0.00012 „
Organic nitrogen in condensation waters 0.00220 „
————————
Sum 0.00244 „
SECOND PERIOD. NO SPRINKLING.
Ammoniacal nitrogen in dilute sulfuric acid 0.000007 gram.
„ „ „ condensed water 0.000007 „
Organic „ „ „ „ 0.000040 „
————————
Sum 0.000054 „
_Conclusions._—The exhalation of nitrogenous compounds takes place with
a certain relative activity, about two milligrams in two months and a
half, as long as the soil is kept moist by sprinkling.
In the second period, without sprinkling, the exhalation is reduced to a
mere trace.
The vessel containing the dilute sulfuric acid placed near the porcelain
pot absorbs only about one-half of the ammoniacal nitrogen set free. The
nitrogen emitted under other forms than ammonia is, in every instance,
greatly superior in quantity, and this is the most important of the
observed phenomena. This is true at least with the kind of soil with
which the experiment was made. With arable soil containing twenty times
as much nitrogen as the soil described above this order is
reversed,[273] the ammoniacal prevailing over the non-ammoniacal
nitrogen volatilized.
These phenomena are doubtless greatly influenced in soil under culture
by microbes, and the lowest orders of vegetation to which are doubtless
due the traces of non-ammoniacal volatile nitrogenous compounds, a sort
of vegetable ptomaines.
=410. General Conclusions.=—In the light of our present knowledge
concerning the methods of nitrogen determination in the soil in the form
of organic compounds and ammonia, moist combustion with sulfuric acid is
to be preferred to the older soda-lime process. For the nitrogen
combined as ammonia, the extraction of the sample with hydrochloric acid
and subsequent distillation with an excess of freshly calcined magnesia,
are recommended. For the study of the progressive decomposition of the
nitrogenous compounds, the various processes devised by Berthelot and
André are the best.
The origin of the nitric acid in the soil, the methods of studying the
various nitrifying organisms, and of estimating the nitric acid
produced, will form the subject of the next part.
NOTE.—At the Eleventh Annual Convention of the Association of Official
Agricultural Chemists, held in Washington, August 23, 24 and 25, 1894,
the following process of soil extraction was adopted as the official
method:
_Preparation of the Sample._—500 grams or more, of the air-dried soil,
which may be either the original soil or that which has been passed
through a sieve of coarser mesh, are sifted upon a sieve with circular
openings one-half millimeter in diameter, rubbing, if necessary, with a
rubber pestle in a mortar, until the fine earth has been separated as
completely as possible from the particles that are too coarse to pass
through the sieve. The fine earths thoroughly mixed and preserved in a
tightly stoppered bottle from which the portions for analysis are
weighed out.
The coarse part is weighed and may be subjected to further examination,
(as in _Bulletin 38, Div. of Chem._, pp. 65, 75 and 200.) It may
sometimes be necessary to wash the soil through the one-half millimeter
sieve with water, in which case proceed as directed on pp. 65 and 75 of
the above _Bulletin_. The use of water is to be avoided whenever
possible.
_Determination of Moisture._—Heat two to five grams of the air-dried
soil in a flat-bottomed, tared platinum dish; heat for five hours in a
water-oven kept briskly boiling; cover the dish, cool in a desiccator,
and weigh.
Repeat the heating, cooling, and weighing at intervals of two hours till
constant weight is found, and estimate the moisture by the loss of
weight. Weigh rapidly to avoid absorption of moisture from the air. An
air-bath must not be used in this determination.
_Determination of Volatile Matter._—The platinum dish and soil used to
determine moisture are used also to determine volatile matter. Heat the
dish and dried soil to full redness until all organic matter is burned
away. If the soil contain appreciable quantities of carbonates, the
contents of the dish, after cooling, are to be moistened with a few
drops of a saturated solution of ammonium carbonate, dried and heated to
dull redness to expel ammonium salts, cooled in the desiccator and
weighed.
The loss in weight represents the organic matter, water of combination,
ammonium salts, etc.
_Extraction of Acid-Soluble Materials._—In the following scheme for soil
analysis it is intended to use the air-dried soil from the sample bottle
for each separate investigation. The determination of moisture, made
once for all on a separate portion of air-dried soil, will afford the
datum for calculating the results of analysis upon the soil dried at the
temperature of boiling water. It is not desirable to ignite the soil
before analysis or to heat it so as to change its chemical properties.
The acid digestion is to be performed in a flask so arranged that the
evaporation of acid shall be reduced to a minimum, but to take place
under atmospheric pressure and at the temperature of boiling water. Any
flask resistant to acids is suitable, but it is not necessary to use a
condenser, as a simple bohemian glass tube eighteen inches in length
will answer the purpose of preventing loss of acid. Where it is not
desired to determine sulfur trioxid, an erlenmeyer fitted with a rubber
stopper and hard glass tube will answer. The flask must be immersed in
the water-bath up to the neck or at least to the level of the acid and
the water must be kept boiling continuously during the digestion.
In the following scheme, ten grams of soil are taken, this being a
convenient quantity in most soils, in which the insoluble matter is
about eighty per cent. If desired, a larger quantity of such soil may be
taken, using a proportionately larger quantity of acid and making up the
soil solution to a proportionately larger volume. In very sandy soils,
where the proportion of insoluble matter is ninety per cent or more,
twenty grams of soil are to be digested with 100 cubic centimeters of
acid and the solution made up to 500 cubic centimeters or a larger
quantity may be used, preserving the same proportions. It is very
important that the analyst assure himself of the purity of all the
reagents to be used in the analysis of soils before beginning the work.
_Acid Digestion of the Soil._—Place ten grams of the air-dried soil in a
150 to 200 cubic centimeter bohemian flask, add 100 cubic centimeters of
pure hydrochloric acid of specific gravity 1.115, insert the stopper
with condensing tube, place in a water or steam-bath and digest for ten
hours continuously at the temperature of boiling water, shaking once
each hour. Pour the clear liquid from the flask into a small beaker,
wash the residue out of the flask with distilled water on a filter
adding the washings to the contents of the beaker. The residue after
washing until free of acid, is to be dried and ignited as directed
below. Add one or two cubic centimeters of nitric acid to the filtrate,
and evaporate to dryness on the water-bath, finishing on a sand or
air-bath to complete dryness; take up with hot water and a few cubic
centimeters of hydrochloric acid, and again evaporate to complete
dryness. Take up as before, filter and wash thoroughly with cold water
or with hot water slightly acidified at first with hydrochloric acid.
Cool and make up to 500 cubic centimeters. This is solution “A.” The
residue is to be added to the main residue and the whole ignited and
weighed, giving the insoluble matter.
The determination of the various components of the solution remains
essentially as described in the provisional methods of the Association
which have already been given.
It is directed that all results of soil analysis be calculated on the
basis of the sample dried to constant weight at the temperature of
boiling water.
AUTHORITIES CITED IN PART SIXTH.
Footnote 189:
Annales de Chimie et de Physique, sixiéme serie, Tome 25, pp. 292, et
seq.
Footnote 190:
L’Analyse du Sol, p. 14.
3. Die Landwirtschaftlichen Versuchs-Stationen, Band 38, S. 311.
Footnote 191:
Bulletin 38, Chemical Division United States Department of
Agriculture, p. 201.
Footnote 192:
Untersuchung Landwirtschaftlich und Gewerblich Wichtiger Stoffe, S.
14.
Footnote 193:
Vid. op. cit. supra.
Footnote 194:
Vid. op. cit. 1.
Footnote 195:
Vid. op. cit. 3, Band 37, S. 279.
Footnote 196:
Journal of the Chemical Society, September, 1880, p. 617.
Footnote 197:
Wanklyn, Philosophical Magazine, Series 5, Vol. 5, p. 466.
Footnote 198:
Vid. op. cit. 1.
Footnote 199:
Traité d’Analyse des Matiéres Agricoles, p. 148.
Footnote 200:
Bulletin 38, Division of Chemistry, United States Department of
Agriculture, pp. 84, et seq.
Footnote 201:
Encyclopedie Chimique, Tome 4, p. 182.
Footnote 202:
Die Landwirtschaftlichen Versuchs-Stationen, Band 37, S. 280.
Footnote 203:
Vid. op. cit. supra, Band 28, S. 229.
Footnote 204:
Comptes rendus, 1890, pp. 290, et seq.
Footnote 205:
Annales Agronomiques, 1890, p. 558.
Footnote 206:
Bulletin 13, Division of Chemistry, p. 590.
Footnote 207:
Bulletin de la Société Chimique, Serie 3, Tome 2, pp. 483, et seq.
Footnote 208:
Zeitschrift für analytische Chemie, Band 3, S. 165.
Footnote 209:
Petermann, L’Analyse du Sol, p. 20.
Footnote 210:
Zeitschrift für analytische Chemie, Band 3, S. 92.
Footnote 211:
Journal of the Chemical Society, March, 1894, p. 141.
Footnote 212:
Agricultural Science, January, 1894, p. 2.
Footnote 213:
American Journal of Science, Vol. 7, 1874, p. 20.
Footnote 214:
Geological and Agricultural Report of Kentucky, Vol. 3.
Footnote 215:
Bulletin 38, Division of Chemistry, p. 77.
Footnote 216:
Op. cit. supra, p. 83.
Footnote 217:
Die Landwirtschaftlichen Versuchs-Stationen, Band 37, S. 311.
Footnote 218:
Zeitschrift für analytische Chemie, Band 3, S. 92.
Footnote 219:
Traité d’Analyse des Matiéres Agricoles, p. 144.
Footnote 220:
Op. cit. 28, pp. 202, et seq.
Footnote 221:
Op. cit. 28, pp. 77, et seq.
Footnote 222:
Op. cit. 22, p. 21.
Footnote 223:
Manuscript communication to author.
Footnote 224:
Annales de la Science Agronomique, Huitiéme Année, Tome 1, p. 278.
Footnote 225:
Die Landwirtschaftlichen Versuchs-Stationen, Band 37, S. 311.
Footnote 226:
Comptes rendus, 1890, p. 289.
Footnote 227:
Thoms, Zur Werthschätzung der Ackererde, S. 120.
Footnote 228:
Le Stazioni Sperimentali Agrarie Italiane, Vol. 16, p. 679.
Footnote 229:
Crookes’ Select Methods in Chemical Analysis.
Footnote 230:
Chemiker Zeitung, Band 13, S. 1391.
Footnote 231:
Annales de Chimie et de Physique, serie sixiéme, Tome 15, p. 309.
Footnote 232:
Vid. op. cit. 37, pp. 270, et seq.
Footnote 233:
Chemiker Zeitung, Band 13, S. 726.
Footnote 234:
Die Agrikultur Chemische Versuchs-Station, Halle, a/S., S. 80.
Footnote 235:
Comptes rendus, Tome 107, pp. 999 and 1150.
Footnote 236:
Die Landwirtschaftlichen Versuchs-Stationen, Band 41, S. 453.
Footnote 237:
Bulletin de la Société Chimique de Paris, 1893, p. 343.
Footnote 238:
Die Agrikultur Versuchs-Station, Halle, a/S., S. 70.
Footnote 239:
Op. cit. supra., S. 68.
Footnote 240:
Op. cit. 37, p. 267.
Footnote 241:
L’Analyse du Sol, p. 20.
Footnote 242:
Op. cit. 1, pp. 303, et seq.
Footnote 243:
Op. cit. 40, S. 114.
Footnote 244:
Bulletin 38, Division of Chemistry, p. 80.
Footnote 245:
Zeitschrift für analytische Chemie, Band 3, S. 92.
Footnote 246:
Chemisches Centralblatt, 1861, p. 3.
Footnote 247:
Berichte der deutschen chemischen Gesellschaft, Band 26, S. 386.
Footnote 248:
Manuscript communication to author.
Footnote 249:
Op. cit. 37, p. 285.
Footnote 250:
Op. cit. 44, pp. 305, et seq.
Footnote 251:
Die Landwirtschaftlichen Versuchs-Stationen, Band 37, S. 284.
Footnote 252:
Op. et loc. cit. 58.
Footnote 253:
Op. et loc. cit. 41.
Footnote 254:
Op. et loc. cit. 37.
Footnote 255:
Op. et loc. cit. 58.
Footnote 256:
L’Analyse du Sol, p. 17.
Footnote 257:
Op. cit. 44, p. 308.
Footnote 258:
Op. cit. 37.
Footnote 259:
Op. cit. 64, Band 40, S. 251.
Footnote 260:
Bulletin de la Société Chimique, May, 1891, pp. 643, et seq.
Footnote 261:
Bulletin 38, Division of Chemistry, p. 204.
Footnote 262:
Bulletin 38, Division of Chemistry, p. 81.
Footnote 263:
Op. cit. 44, March, 1891, pp. 393, et seq.
Footnote 264:
Op. cit. 58, Band 31, S. 525.
Footnote 265:
Relatorio Annual do Instituo Agronomico do Estado de San Paulo
(Brazil), 1892, p. 107.
Footnote 266:
Op. cit. 37, pp. 253, et. seq.
Footnote 267:
Op. cit. 44, Tome, 25, pp. 299, et seq.
Footnote 268:
Petermann, L’Analyse du Sol, p. 17.
Footnote 269:
Op. et. loc. cit. 76.
Footnote 270:
Die Landwirtschaftlichen Versuchs-Stationen, Band 33, Ss. 247, et seq.
Footnote 271:
Op. cit. 44, Tome 25, pp. 327, et seq.
Footnote 272:
Op. cit. 44, Tome 25, pp. 330, et seq.
Footnote 273:
Op. et loc. cit. supra.
PART SEVENTH.
THE ORIGIN AND ESTIMATION OF OXIDIZED NITROGEN IN SOILS, RAIN AND
DRAINAGE WATERS.
=411. Introductory Considerations.=—The estimation of oxidized nitrogen
in the soil would properly find a place in the preceding part; but on
account of the late progress in our knowledge of the source of this
indispensable and costly plant food it has become necessary to give it
especial attention. The present part will, therefore, be devoted to a
brief statement of our present knowledge in respect of the origin of
oxidized nitrogen, a description of the nitrifying ferments and methods
for their isolation and determination and finally the most approved
methods of estimating the ammonia, nitrous, and nitric acids formed
thereby both in the soil and the waters pertaining thereto or proceeding
therefrom. It is scarcely necessary to caution the reader not to
consider this part in any sense a treatise on the bacteria active in
soil chemistry. Its object is rather to place in the hands of the soil
analyst data which will enable him to intelligently study the soil
phenomena depending on these organisms and to determine the extent and
character of their biological and chemical functions. These are matters
which, up to the present time, have found no place in manuals dedicated
to agricultural analysis.
=412. Organic Nitrogen in the Soil.=—With the exception of the small
quantities of nitric acid added to the soil directly by rain water, the
whole of the supply of this substance is derived from the products of
the oxidation of nitrogenous bodies. These products are either stored as
the results of past nitrification or are formed synchronously with their
consumption by the growing plant. Nitrogenous compounds are present as
organic vegetable or animal remains and as humus. All vegetable and
animal material deposited in or on the soil contains more or less of
these proteid or nitrogenous matters while the amount of nitric acid
supplied in this way is probably represented entirely by the quantity in
the organism of the plant or animal and unabsorbed at the time of its
death. In other words it is not demonstrated that nitrates or nitrites
are in any sense a special product of plant growth save in the case of
nitrifying organisms themselves which are supposed to be of a vegetable
nature. Animal organisms do not in any sense assimilate nitric nitrogen.
With most plants, the quantity of proteid nitrogen which they can
deliver to the soil is in no case greater than the sum of organic and
nitric nitrogen supplied in their food and they can therefore be
regarded only as the carriers and conservers of this substance. On the
other hand there are some plants notably those belonging to the
leguminous family which permit of the development on their rootlets of
colonies of bacteria which have the faculty of rendering atmospheric
nitrogen available for plant growth. Whether or not there exist plants
other than the micro-organisms mentioned which are capable of directly
oxidizing and fixing atmospheric nitrogen is still an unanswered
question. It is not probable, however, that the difficult task of
oxidizing atmospheric or free nitrogen would be accomplished in nature
in only one way. In fact it has already been established that organisms
do exist which are capable of oxidizing free nitrogen in a manner wholly
independent of other plant life and to produce weighable quantities of
nitric acid when developed in media of mineral matters and pure
carbohydrates to which free nitrogen has access. It is, therefore, fair
to assume that the fixation of free nitrogen is a function of chemical
activity quite independent of ordinary plant life and that the
leguminous plants take no further part in this process than that of
providing in their radical development a favorable nidus for the growth
of the nitrifying organism.
By the action of denitrifying organisms a portion of the nitrogen of
nitric acid is constantly restored to a free state, a far larger
portion, perhaps, than is fixed in the atmosphere itself by the action
of electricity. Were it not, therefore, for the activity of the
nitrifying ferments the stores of nitrogen available for growing plants
would constantly become less. Instead of this being the case, however,
it is probable that the contrary is true and that, by a wise system of
agriculture, the total nitrogen at the disposal of plants may become
greater and greater in quantity.
=413. Development of Nitric and Nitrous Acids in Soils.=—Owing to the
solubility of nitrates there can be but little accumulation of them in
soils in those countries where there is any considerable amount of
rain-fall. On the other hand in arid regions there may be found
extensive deposits of nitrates. The occurrence of a certain quantity of
nitrates in the soil, however, is essential to the growth of plants.
Until within a few years little was known of the origin of nitric acid
in the soil. The presence of nitrates in drainage waters was well
established, likewise the consumption of nitric acid by the growing
plant, but the method of its supply was unknown. In a general way it was
said that the nitric acid came from electrical action and the oxidation
of the albuminous bodies in the soil, but without specifying the manner
in which this change takes place. The researches of Schloesing and
Müntz, of Springer, Winogradsky, Frankland, Warington and others have
demonstrated the fact that this oxidation is caused by means of bacteria
and that the nitrates formed can be consumed and destroyed by other
species of this organism. In the one case the process has been called
nitrification and in the other denitrification.[274]
The influence of these low organisms both in producing fertility in a
soil and maintaining it in a state of fertility is of the highest
importance.
=414. Conditions Necessary for Nitrification.=—In order to properly
understand the reasons for many of the steps in investigating a soil for
nitrifying organisms, it will be useful to state the general conditions
on which nitrification depends.
The nitrifying organism, like every other one, first of all feels the
necessity for food. In general, food which is given to microbes of all
kinds consists of some organic matter together with the addition of
mineral substances necessary to growth. These substances in general are
phosphoric acid, potash, and lime. Of these articles of bacterial food
phosphoric acid seems to be the most important. With the nitrifying
organisms, however, it has been found that the organic matter can be
omitted. In fact, as will be seen further on, the omission of organic
matter supplies the best condition for the proper isolation of the
organisms. In other words some forms of the nitrifying organisms have
the property of subsisting wholly on mineral substances, _i. e._, are
true vegetables.
The presence of oxygen is also necessary to the growth of the common
nitro-organisms. In an atmosphere deprived of oxygen or in which the
oxygen is reduced to a very low percentage, the process of nitrification
is retarded or stopped as the oxygen diminishes or disappears.
The presence of a base with which the nitrous or nitric acid formed may
unite is also essential to the proper conduct of the process. For this
reason the nitrification should take place in a solution which is feebly
alkaline or in the presence of a base which can be easily decomposed so
that no acidity can take place. Calcium carbonate is a base well suited
to favor the nitrifying process and its presence in a soil favors the
rapid oxidation of proteid matter. The mistake must not be made,
however, of supposing that an excess of alkali would favor
nitrification. The contrary is true. A slight excess of alkali may
prevent nitrification altogether when it is due to the common organisms
present in an arable soil. It may be that in soils charged with alkali a
different organism exists which is capable of exercising its functions
when the alkali is in excess.
The temperature to which the nitrifying body is subjected is also a
matter of importance. The nitrifying organisms have the property of
remaining active at lower temperatures than most bodies of their class.
On the contrary their action is retarded and destroyed by high
temperatures. The most favorable temperature for nitrification is about
that of blood heat; _viz._, 37°. At 50° the organism shows very little
activity and at 55° its activity ceases altogether. Nitrification,
however, according to Warington, cannot be started in a solution if the
initial temperature is 40°.
Desiccation has the same retarding influence on nitrification that a
high temperature has. Even thoroughly air-drying a soil may destroy its
nitrifying qualities.
Darkness is also necessary to the proper progress of nitrification. In a
strong light, the activity of the organism is very much diminished or
destroyed altogether. A bright light like sunshine may even stop
nitrification which has set in.
=415. Effect of Potassium Salts on Rate of Nitrification.=—Dumont
and Crochetelle have described some experiments to determine the
effect of potassium salts alone and in combination with lime on
nitrification.[275]
Soil rich in vegetable mold (18.5 per cent of humus and 0.29 per cent of
lime) was treated with varying amounts of potassium sulfate and
carbonate and kept for twenty days at 25°. In the untreated soil the
amount of nitric acid produced was twenty-five parts per million. When
potassium carbonate was applied in quantities of from one-tenth to six
per cent the amount of nitric acid increased from forty-seven parts per
million to 438 parts when four and one-half per cent of the potassium
salt were used. Larger quantities caused a decrease in the amount of
nitric acid produced. Very little effect, on the contrary, was produced
by the action of potassium sulfate. When one-half per cent was employed
the quantity of nitric acid formed rose to fifty parts per million,
while with quantities as high as five per cent it fell below the normal;
_viz._, twenty-five parts per million.
When calcium carbonate was added to the soil in conjunction with
potassium sulfate there was a marked increase in the amount of nitrogen
oxidized. The activity of potassium sulfate in promoting nitrification
is therefore increased by the presence of the calcium salt, potassium
carbonate and calcium sulfate being formed.
=416. Production of Nitrous and Nitric Acids.=—In the following pages
the study of the methods of isolating the nitrous and nitric ferments
will be considered as one process, the final isolation of the two
classes of bodies being the result of their synchronous cultivation in
appropriate media. The special process of the production of ammonia by
oxidation is not so well-known, and will therefore be described in
brief.