30 MANURING EXPERIMENTS WITH PADDY RICE (SECOND YEAR). 
be applied per tan in addition to the common manures may 
between 1-1.5 kwamme 19 the smaller dose being sufficient 
for fields formerly frequently manured with rice bran, fish 
manure or oil cakes, the larger in those cases where green 
manure, farmyard manure, night-soil, etc., are principally used. 
Next, as to manurial value, come the two kinds of bone 
dust. Of these the steamed sort had a slightly lower effect 
than the crude kind, probably because the former had lost some 
of the gelatogenous substance during manufacture which is 
supposed to play an essential part in the dissolution of the 
bone phosphate in the soil. In general, their effect was, as 
already mentioned, very high, surpassing that of the phosphoric 
acid of Thomas phosphate and Peruvian guano ; but whether 
this will also be so on soils in a different condition, especially 
on irrigated heavy land, is doubtful, and requires further inves¬ 
tigation. In cases similar to ours 10 kwamme of finely powdered 
bone dust to the tan will suffice. It is advisable to incorparate 
this manure rather early with the soil or to ferment it slightly 
before its application, especially if it consists of coarse grains, 
and is not free from fat. As the bone manure contains besides 
phosphoric acid about 3-5% nitrogen, the quantity of the other 
fertilizers to be applied may be correspondingly diminished. 
The Thomas phosphate proved to be only slightly inferior to 
the bone dust and is suited to all kinds of irrigated soils. Per 
tan about 2-3 kwamme of phosphoric acid in this form of 
manure will secure a good crop. 
Peruvian guano and bone ash had both a rather low effect, 
and are not to be recommended either for rice or for dry 
land crops. After treatment with sulphuric acid, i.e. in the 
form of superphosphate, they will, of course, exert a good 
effect, and should always be converted into this kind of 
fertilizer. Peruvian guano is, however, at present too expen¬ 
sive to be imported. 
The least effect was obtained by the application of phosphorite 
19 i kwamme = 3.7565 kilogrms. 
