May 2, 1904.] Supplement to the "Tropical Agriculturist." 
791 
One of the first signs of a lack of potash in the 
soil is a decided cessation in plant growth, with- 
out other apparent cause of trouble. The plants 
of such soils will often have their normal green 
colour, but will make very little starch or sugar, 
and almost no protein or nitrogenous matter. 
In one of the plots of grass at the Rothamsted 
experimental station, plot 10, half-aii-acre ai'ea, has 
received for 47 years (1856-1903) 400 lb. per acre 
of ammonia salts. It also received during the 
first six of the 47 years a mineral manure, con- 
taining phosphatef, soda and potash. But dur- 
ing the remaining 41 years the potash has been 
omitted from the manuriul mixture, and an in- 
creased amount of soda was applied instead. 
The effect of the exclusion of the potash from 
the manure was greatly to reduce the amount of 
produce and to lessen the number of plant species 
developed. Further, there has been a great 
reduction in the tendency to stem formation, the 
herbage being more leafy and dark green in colour, 
and remaining backward and unripe, . while the 
adjoining plot (9), with the potash supply, would be 
fit to cut. 
With the less amount, and more leafy and 
consequent unripened condition of the produce, 
the percentage of nitrogen in the dry substance 
of the hay is much higher; that is to say, the 
nitrogen of the manure was taken up, and the 
green chlorophyll of the plant was formed, but 
the assimilation of carbon and starch and sugar 
formation were restricted in defect of sufficient 
potash. The change in the composition of tlie ash 
of the hay is more striking still. 
Thus, during the six years of the application of 
the potash, the ash when submitted to chemical 
analysis contained 29 5 per cent of potash, but 
over the remaining years of the exclusion of the 
ingredient potash from the manure, the ash con- 
tained only 17 per cent, a reduction of 12*5 per 
cent. 
On the other hand, during the six weeks of the 
potash supply, the ash contained only 5'8 per 
cent of sodo, but during tlie remaining years it 
contained 15 per cent., or about twice and a half 
as much. Still, however, the soda did not attain 
to the proportion of the potash. 
With the deficiency of potash supply there were 
somewhat higher percentages of both lime and 
magnesia in the ash of the hay. 
The interest of the variations in the percentages 
of the ash, and in the amount of constituents 
found in the produce per acre due to the variation 
in the supply, is, of course, in the fact that the 
differences are associated with differences in the 
botanical character and in the organic composition 
of the produce — that is, in the description of 
plants encouraged and in the character of their 
development, whilst upon these depends the value 
of the produce for stock-feeding purposes. 
The cessation of the application of potash was 
not only followed by less amounts of total hay, as 
already stated, but tlie produce became almost 
exclusively grassy, to tiie exclusion of clovers, and 
at the same time tiie better class or grasses died 
out, and some of the inferior kinds became very 
prominent, 
But, independently of the description of plants 
encouraged, the produce from the want of potash 
showed a leafy dark green and immature condition, 
to which the deterioration of the hay was character- 
istically due — in fact, in defect of sufficient supply 
of potash tlie merely vegetative as distinguished 
from the reproductive and maturing tendencies 
of growth predominated, the result being a 
relatively deficient production of starchand sugar. 
— The Field. 
BACTERIA AND THE NITROGEN PROBLEM. 
By George T. Moore, 
Physiologist, Bureau of Plant Industry, U.S.A. 
There is probably no fact in plant physiology 
which has been more firmly established than 
tlat all plants must have nitrogen in order to 
ihrive, and that under normal conditions this 
nitrogen must be obtained through the roots in 
some highly-organised form. It is not necessary 
to discuss this point, for practical experience 
demonstrates its truth every time a soil is 
exhausted by any crop, and the farmer testifies 
to his belief in this fact when he tries to re- 
establish the fertility of his ground by adding 
some fertilizer rich in nitrogenous matter. While 
there are certain other substances, such as 
phosphoric acid, potash, iron, etc., which plants 
must have and can only obtain through the soil, 
the demand for nitrogen is so much greater and 
in one sense so much more important, that the 
question of the available nitrogen supply in the 
world has come to be looked upon as lying at 
the very foundation of agriculture and demanding 
tlie most careful consideration. Since the con- 
ditions of life in the civilized quarters of the 
globe are such as to cause a constant loss of 
nitrogen, there have been some wlio have predicted 
what has been termed a " nitrogen famine," 
which is to occur within the next forty or fifty 
years, and the possibility of such a catastrophe 
lias been very graphically portrayed. On the 
other hand, there are investigators who feel that 
the possibility of such a condition has been much 
exaggerated, and that the amount of nitrogen 
in the soil can never be exhausted to such an 
extent as to affect the crop-producing power of 
the earth, In order that we may be able to 
form a more definite opinion upon the subject, 
it may be well to look at some of the ways 
in which nitrogen is lost, and then see how it 
may be reclaimed. 
In the first place, the conditions of life on 
the ordinary farm are such as to cause the 
constant loss of this valuable element through 
the removal of the crops taken from the soil. 
If every crop that grew on the land could be 
returned to it, nature has made provision for 
getting it back in suitable form for plant food. 
In the case of nitrogen neither plants nor animals 
are able to produce this substance directly in 
an available form. It is necessary that certain 
bacteria take hold of plant and animal products, 
and by means of peculiar changes produce nitrates 
from their fats, sugars, starches, etc- With- 
