IG 
IMPERIAL COLLEGE OF 
treated with a solution of ammonium chloride of a content 
of nitrogen equivalent to the last mentioned quantity of 
urea, it absorbed a considerable proportion (0.183 grams.) 
of nitrogen. By another experiment in which a solution 
of 8.1654 °/ 0 urea was filtered through a burette containing 
the same kind of soil, the same result was arrived at. Soils 
have consequently not the poiver of absorbing urea. 
This fact suffices to explain the injurious effect of fr 
urine or excreta in the following way : As the urea remain 
in a dissolved state after top-dressing the crops, the concen¬ 
tration of the fluids in the soil may become so strong that the 
absorption of water by the roots is interfered icith, whence the 
green organs are caused to wilt. Human urine contains, ac¬ 
cording to the average of many determinations, about 2 °/ 0 of 
urea besides 1.5 °/o common salt and sulphates, and if 
diluted even with a threefold volume of water, it 
remains still concentrated enough to hinder the plants 
from absorbing sufficient water, since in numerous experi¬ 
ments on the growth of plants in nutritive solutions, 
concentrations of 0.5 °/o caused failures. On the other 
hand, well decomposed urine reduces the diffusion of 
water into the roots but in exceptional cases, viz. if the 
absorptive power of the soil for basic nutrients is very 
low and if it is poor in moisture or liable to dry up. In 
such soils, however, every easily soluble manure may have 
or acquire that influence. 
The application of fresh excreta to crops is also ob¬ 
jectionable from another point of view. Since the urea 
which constitutes the principal nitrogenous and effective 
ingredient of the urine, remains dissolved in the fluids of 
the soil, it is liable to be washed doivn by rain and thus to be 
carried beyond the reach of the roots. It is true, the 
micro-organisms of the excreta and those contained in the 
soil will gradually convert the whole of the urea into 
carbonate of ammonia, but this process takes some time, 
4 
