836 The Conservation of Farm-yard Manure. 
apart for these trials, which were carried out with potatoes and 
wheat. The dung was applied at the rate of 40,000 kilos, per 
hectare (about 16 tons per acre). 
“ The first series consists in a comparative trial of the action of 
various manures on strong clay land, planted in the first year with 
potatoes, and in the following year with wheat, without any fresh 
addition of dung. The soil was naturally a rich one. The second 
series was carried out on light land, undunged for four years, and 
therefore poor in available elements of fertility. 
“ The excess of weight of the crops grown with the various dungs, 
over and above the yield of three plots left unmanured for the sake 
of comparison, was as follows, expressed in percentage of excess 
(the unmanured plots being taken as 100) : — 
First Series — Clay Soil. 
Feeding- 
■box manure 
In excess of 100 on 
unmauurcd land 
Kept without 
addition 
Treated 
with 
earth 
Treated with 
phosphatic 
gypsum 
Treated 
with potash 
salts 
Potatoes (tubers) 
8-1 
27'8 
336 
16 
Grain . 
28-1 
28-1 
21-1 
14-9 
Straw and chaff . 
6-2 
131 
11 
11-7 
“ The untreated dung thus gave, on this clay soil, in the second 
season only, an excess of crop equal to that which the dung pre- 
served with earth had produced in the first crop — confirming the 
opinion previously expressed by Holdefleiss on the favourable 
influence of the partial nitrification undergone by dung when it is 
covered with earth for six months.” 
Second Series — Light, Open Soil. 
“ The soil on which these experiments were made is very free ; 
the surface or arable soil having a depth of 14 in. to 16 in. 
The field had borne barley as the previous crop ; it had received no 
manure for four years. Plots of 8-5 ares (4 acre) were manured with 
the various dungs at the rate of 40,000 kilos, per hectare (about 
16 tons per acre) ; three plots being left unmanured for the sake 
of comparison : — 
Feeding-box manure 
In excess of 100 on 
immamircd laud 
Grain .... 
Straw and chaff . 
Without 
addition 
42 
27 
Treated 
with 
earth 
74 
66 
Treated with 
phosphatic 
gypsum 
103 
50 
Treated 
with potash 
salts 
US 
69 
“Here the results are even more appreciable than in the first series, 
as they should be, on account both of the poverty of the soil and of 
its mechanical condition, which allowed, in the first year, a more 
rapid decomposition of the dung. The best result was obtained by 
the use of the potash-treated dung, the crop from which more than 
doubled the grain yielded by the unmanured soil. Next to this 
comes the phosphated dung. The earth-treated dung occupies only 
