396 
AMERICAN AGRICULTURIST. 
Nitrogen as Nitric Acid. 
BY .7. B. LAYVKS, LL. B., ROTIIAMSTED, ENGLAND. 
In a previous communication published in 
the August number of the American Agricul¬ 
turist, I pointed out that Nitrogen, in the , 
form of Nitric Acid, was an ingredient in 
soils which was constantly being produced, 
was very soluble in water, and very easily 
washed out of the land. It was further as¬ 
sumed that Nitrogen in this form was taken 
up by plants, although no direct evidence 
was brought forward to establish the fact. 
I propose now to show the effect of Nitro¬ 
gen applied as Nitrate of Soda upon various 
crops of the farm. If a farmer, by way of 
experiment, were to supply his soil abun¬ 
dantly with mineral manures, but, as regards 
Nitrogen, were to leave the crop grown to 
depend on the amount of that substance it 
could obtain from natural sources, he would 
find that, sooner or later, the produce would 
decline; and if the seasons were all exactly a- 
like, this decline, although very slight, might, 
with sufficient care, be measured early in the 
experiment; as however the seasons differ in 
what we call fertility, it is quite possible that 
he might, after several years, obtain crops 
which were even larger than some of those 
grown at the beginning of the experiment; 
the decline, however, in the course of time, 
would be so marked that even the most fertile 
season would only yield a reduced produce, 
and the reduction would be far more rapid 
were it not for the efforts put forth by the 
plant to economize its food. No family, re¬ 
duced by some reverse of fortune from afflu¬ 
ence to poverty, ever made greater efforts 
than the plant to maintain a decent appear¬ 
ance before the world on reduced means of 
subsistence. At Rothamsted, by the aid of 
chemistry, we have been enabled to study the 
internal arrangement of the plant, and can 
see how, when scarce, it economizes one im¬ 
portant element of food which it prefers, and 
substitutes another which is less palatable 
but more abundant. Among our experiments 
we have one upon four crops very dif¬ 
ferent in character, which for a long period 
of time have received a large annual supply 
of mineral food, Potash t ^aa, Magnesia, 
and Phosphates. It will be seen from the 
table below that there is no material differ¬ 
ence in the amount of dry matter, of mineral 
matter, or of Nitrogen contained in the pro¬ 
duce grown upon an acre of land by any of 
these four different crops :— 
About 
Potatoes .. 170 bushels .. 
Dry 
Matter 
per acre. 
2,108 
Mineral 
Matter, 
per acre. 
99 
Nitrogen 
per acre. 
17 
Mangolds. 
5* tons. 
1.079 
96 
15 
Wheat. 
12 bushels .. 
1,900 
99 
15 
Barley.... 
15 bushels .. 
1.900 
99 
15 
Mean. 1,879 98 15* 
It will be observed that the minerals and 
Nitrogen form about six per cent of the whole 
crop, and we may consider that this portion 
is derived from the soil, while the remaining 
94 parts are obtained from the atmosphere. 
The Nitrogen and minerals may be described 
as the working machinery of the plant, by 
which carbonic acid is decomposed and the 
carbon fixed. • 
The crop of potatoes grown by the minerals 
amounted to a little over 4 (short) tons per 
acre ; the application of 550 lbs. of Nitrate of 
Soda, in addition to the minerals, increased 
the crop to nearly double this amount. The 
largest crop grown in any one year by means 
of the Nitrate and minerals combined, was 
about 10 tons, and as the minerals alone gave 
about 4*/a tons, we have an increase of 5'/ 3 
tons due to the action of the Nitrate. One 
hundred pounds of Nitrate of Soda contain 
15 l /o lbs. of Nitrogen, and one ton of potatoes 
contains 5 lbs. of Nitrogen ; if, therefore, all 
the Nitrogen of the Nitrate was recovered in 
the crop, an increase of 3 tons of potatoes 
should be obtained by the application of one 
cwt. of Nitrate. Our largest increase, as I 
have pointed out, was 5'/s tons, but as this 
was the result obtained by the application of 
550 lbs. of Nitrate, about two-thirds of the 
amount applied was not recovered in the 
crop ; of this unrecovered portion a certain 
part would have been employed in the growth 
of the leaves, and stem, and another in the 
roots—a very considerable proportion being 
either destroyed or washed out of the soil. 
Let us now make a comparison with an¬ 
other crop. Barley, grown for 30 years in 
succession with mineral manures alone, has 
given an average produce of 34 bushels, but 
the addition of 275 lbs. of Nitrate of Soda to 
the minerals has raised the average produce 
to 46 bushels ; the increase due to the Nitrate 
or Soda was therefore 32 bushels, and during 
the last season, 1880, which was very favor¬ 
able to the barley crop, the increased yield 
obtained by the Nitrate of Soda over the 
minerals alone was 33 bushels, the minerals 
giving 28 bushels, and the minerals and Ni¬ 
trate 61 bushels per acre ! The weight of 33 
bushels of barley, including the straw, would 
be nearly 4,000 lbs., containing about 1 per 
cent of Nitrogen : the 33 bushels of barley 
would therefore contain about 40 lbs. of 
Nitrogen; and as the 275 lbs. of Nitrate of 
Soda would supply about 42 lbs. of that sub¬ 
stance, it is evident that under very favorable 
circumstances the greater part of the Nitro¬ 
gen supplied may be recovered in the crop. 
In agriculture, however, we can only deal 
with averages, and as the average increase 
due to the Nitrate did not amount to more 
than 22 bushels, the amount of Nitrogen re¬ 
covered in the increased produce would be 
very little more than one half of that sup¬ 
plied in the Nitrate. The influence of the 
Nitrate applied artificially to crops, is not 
difficult to understand. All soils, in addition 
to the mineral food of plants, contain more 
or less Nitrogen in combination with carbon. 
Every year a portion of this organic Nitrogen 
is converted into Nitric Acid, which unites 
with lime or some other alkaline matter in 
the soil. Part of this Nitrate of Lime becomes 
the food of plants, and part is washed out of 
the soil or is otherwise lost. If more nitrates 
are formed than the growing plant can util¬ 
ize—owing to a deficiency of the necessary 
mineral food in the soil—the Nitrogen ac¬ 
cumulates in the plant, the result being 
visible to the eye from the dark-green color 
it imparts to the foliage. Owing to the long 
period of time during which the crops upon 
my fields have been kept under the separate 
manure ingredients, they show, when young, 
every shade of color, from a pale yellowish- 
green to a dark greenish-blue. 
When a large crop is obtained by the ap¬ 
plication of a mineral manure such as Potash 
or Phosphate, it is due to the fact that the 
liberated Nitric Acid is quite equivalent to 
the growing power of the mineral food in 
the soil, available for the use of the crop. 
After a few years application of these min¬ 
erals alone, it would be found that they were 
less effective than when first used; they 
[October, 
would then accumulate in the soil, only to 
become the food of plants when aided by an 
artificial supply of Nitrogen. In one of our 
experiments upon permanent wheat, 8,000 
lbs. of Sulphate of Potash, and the same 
quantity of Superphosphate of Lime have 
been applied to one acre of land during the 
last 38 years ; almost the whole of this amount 
is now lying in the soil within reach of the 
crops, but unavailable for the use of the 
plant, owing to the absence of soluble Nitro¬ 
gen. Plants then, derive their Nitrogen prin¬ 
cipally from Nitrate of Lime formed from 
the organic Nitrogen existing in the soil; but 
if a larger amount of produce be required 
than this Nitrate is competent to supply, re¬ 
course may be had to Nitric Acid in the form 
of Nitrate of Soda, or Ammonia, or Organic 
Nitrogen, and the value of these substances 
is, in some degree, in proportion to the readi¬ 
ness with which they are converted into 
Nitric Acid. 
The general idea that Nitrate of Soda acts 
as a stimulant to vegetation is incorrect. 
The action of Nitrate of Soda is due to the 
fact of its furnishing plants with one very 
important element of their food, Nitric Acid ; 
the soil furnishes the same substance, but not 
always in sufficient quantities, and the ques¬ 
tion as to when it will be profitable to employ 
so costly a substance, is one that cannot be 
answered without a full knowledge of all the 
circumstances of the particular locality. 
My experiments show that, even when lit¬ 
tle or no loss of Nitrogen takes place from 
washing, a very considerable proportion of 
the amount supplied is not recovered in the 
crop; it is evident, therefore, that in the 
States, where nitrate is as costly as it is in 
England, and where a lower range of prices 
prevails for farm crops, some caution must 
be used in its application. 
Swine Raising—A Different System 
Desirable. 
BY’ COL. F. D. CURTIS. 
The American Agriculturist has so long 
recommended improved pigs to its readers, 
with Essex as its model, that we apprehend 
a different doctrine may be considered as 
Swine heresy. We shall write of pigs from 
a practical standpoint, which embraces not 
only raising them for breeding but for slaugh¬ 
ter. We do not consider the little chunky 
breeds to be the most profitable. There are 
two decided objections to them; want of 
growth, and unfitness for food. There are 
too many pig-pens or pig prisons. A warm, 
clean, and roomy pig-pen in winter is wise. 
During the season of cold weather, pigs want 
a home where they can burrow and keep out 
of the cold, as this is their nature ; and when 
they are kept warm, it makes a decided sav¬ 
ing in the amount of feed required. In sum¬ 
mer the circumstances are all different, as 
this is the season for growth. Pig raisers 
have generally adopted a system to make the 
most rapid increase. They have supposed this 
to be the most profitable. They acted upon 
the principle that the more food which could 
be stuffed into a pig the better, and breeders 
have been governed by the same idea, and 
have endeavored to condense pigs as far as 
possible, reducing the bone, muscle, and other 
parts to fat, so that the modern improved pig 
has become little else than a mass of animated 
lard. Such pigs are not fit to eat, and people 
show their good sense by not eating them. 
