106 
FLORIDA STATE HORTICULTURAL SOCIETY 
tends to de flocculate clay soils and serious¬ 
ly injure their physical condition. On 
acid soils nitrate of soda tends gradually 
to correct the acid condition; and if the 
soil is of such a physical character that it 
is not likely to be injured by the residual 
sodium carbonates, the after effect from 
the use of nitrate of soda is beneficial. 
Sulphate of ammonia is not so subject 
to leaching as nitrate of soda; yet if it 
were used as the exclusive source of ni¬ 
trogen on a highly calcareous soil, there is 
a possibility that so much ammonia would 
be liberated at once that some of it might 
escape into the air and be lost, or even, 
under such conditions, cause direct injury 
to plants, many of which are very sensi¬ 
tive to its presence in large quantities. 
Sulphate of ammonia also tends to make 
soils acid on account of the fact that the 
ammonia is largely changed to nitric acid 
in the soil, which further adds for a time 
to the marked acidity created by the resid¬ 
ual sulphuric acid that was combined with 
the ammonia at the outset. 
Calcium nitrate and potassium nitrate 
are both subject to ready loss by leaching 
in open sandy soils in case heavy rains 
•occur. For crops which are greatly in 
need of lime, especially when they are 
grown on acid soils, calcium nitrate has 
distinct advantages; whereas for certain 
root crops which can use some soda, in 
case the supply of potash becomes de¬ 
ficient, nitrate of soda may be a more 
efficient or better source of nitrogen. 
If calcium cyanamid is introduced into 
fertilizers in small amounts under cer¬ 
tain chemical conditions, the nitrogen 
may be largely transformed into urea, a 
most valuable organic source of nitrogen 
for plants. On the other hand, if it is 
introduced into fertilizers under other 
conditions or in large quantities or if it is 
applied directly to the soil under the usual 
conditions, large amounts of dicyanodi- 
amid are formed from it—a compound 
which is highly toxic to plants. It is on 
this account that calcium cyanamid of it¬ 
self is usually considered unsuited for use 
as a top dressing or direct application to 
growing crops or trees. It is on this ac¬ 
count, also, that it must be applied two to 
three weeks before the seed is sown in or¬ 
der not to injure the young rootlets. 
There is a possibility that in the near 
future ammonium chloride may be placed 
on the market as a source of ammonia. 
If this occurs, it will have to be used with 
even more care than sulphate of ammo¬ 
nia, especially on acid soils. 
The important feature in connection 
with fertilizers is to have such quantities 
and such proportions of various materials 
used as to exert the best and most favor¬ 
able influence upon plant growth, taking 
into account, also, the effect of the ferti¬ 
lizers upon the physical and chemical con¬ 
dition of the soil. It is possible with a 
clear understanding of these points to use 
such proportions, for example, of certain 
nitrates, ammonium salts or other mate¬ 
rials, as to avoid the ill effects which may 
arise from their exclusive use as sources 
of ammonia; for when combined in the 
proper proportions and in a proper man¬ 
ner, the various drawbacks mentioned 
may be largely or wholly avoided, by 
making the effect of one substance coun¬ 
teract the unfavorable effect of another. 
A further interesting phase of the ni¬ 
trogen problem is that of denitrification, 
