IMPERIAL COLLEGE OF 
'22 
be added to the field, otherwise the nitrogen of the excreta 
cannot contribute effectually to the growth of the crop ; 
indeed it may cause a scanty formation of grain and lodging. 
The following table gives the results of similar calcu¬ 
lations for other crops. 
Produce corresponding to 
the nitrogen contained in 
1000 liters of night-soil. 
Phosphoric acid 
Needed for 
Required for 
supple- 
Grains. 
Kilogrms. 
Straw. 
Kilogrms. 
this pro¬ 
duce. 
Kilogrms. 
menting the 
excreta. 
Kilogrms. 
Wheat . 
106 
150 
7.8 
6.5 
Barley . 
127 
190 
7.1 
5.8 
Oats . 
106 
175 
8.0 
6.7 
Maize. 
127 
175 
9.3 
8.0 
Buckwheat . 
127 
195 
12.7 
11.4 
Rice . 
124 
190 
5.3 
4.0 
Rape. 
64 
tubers 
180 
foliage 
10.0 
8.7 
Potatoes. 
800 
roots 
90 
foliage 
9.5 
8.2 
Carrots . 
1120 
170 
9.3 
8.0 
It will easily be seen from these figures that human 
excreta do not constitute a complete fertilizer, since for 
none of the above common crops do they contain phos¬ 
phoric acid enough to secure a good growth, and a similar 
calculation would prove, that they are also too poor in 
potash to supply by themselves the demand of crops. The 
amounts given in the table of phosphoric acid needed to 
supplement the night-soil, represent phosphoric acid freely 
soluble in water and should be regarded as the minimum 
quantities to be added, because on the one side a consi¬ 
derable part of the phosphates of the excreta exists in an 
insoluble state and cannot come into contact with the roots 
when the dung is applied as top-manure, the insoluble 
portions being then retained in the superficial layers of the 
soil, whither the roots do not grow ; and on the other side 
