106 The N.Z. Journal of Science and Technology. [June 
returns when applied to the utilization in the soil of finely ground phos¬ 
phate rock, which experiment and experience have demonstrated our New 
Zealand soils require. It is well known that phosphate rock is more 
effectively utilized in the soil and by the plant when mixed with organic 
matter ; the organic matter while undergoing decomposition releases carbon 
dioxide, which hastens the solution of the insoluble phosphate. It is thus 
that the animal ammoniates fulfil their purpose, by adding their increment 
of available nitrogen for plant-food, and in addition supplying the soil 
bacteria with food which stimulates their activity. In turn, the soil 
bacteria by their activities carry out their work in dissolving the inert 
mineral phosphatic compounds, which are then made available as food 
for the growing plant. When regarded in this light, the tankage and other 
ammoniates play a dual role in agricultural development. Support to 
this view is added when the results of the use of certain phosphatic guanos 
containing organic matter is considered, results which cannot be attributed 
merely to the phosphatic content. The guanos referred to are those 
from Ichaboe, ITuon, and Walpole. 
No useful purpose can be served by discussing the relative importance 
of various fertilizers for different crops and soils. Too often such fertilizers 
are supplied for trade reasons only, and not in order to meet, the specific 
agricultural need which their brand would indicate. 
In connection with the utilization of ground mineral phosphate for 
mixing purposes, it is important to see that this material is ground finely 
enough for use as a plant-food. Experiments have shown that the agri¬ 
cultural efficiency of a finely ground mineral phosphate is not increased by 
grinding finer than will enable it to pass through a 100-mesh sieve ; for 
practical purposes a standard of 70 per cent, through a 100-mesh sieve 
seems to be a reasonable demand. 
The following particulars have been taken from actual registrations of 
fertilizers sold in New Zealand during 1920-21 :— 
Table VII. 
Nitrogen. 
Phosphoric 
Anhydride. 
Potash. 
Per Cent. 
Per Cent. 
Per Cent. 
(x.) Turnip 
. . 1-00 
18-00 
• . 
ly-) 
.. 0-90 
18-76 
0-33 
(z.) 
.. 140 
16-90 
• a 
(x.) Grain 
. . 1-00 
11-25 
e a 
( y •) „ 
.. 0-75 
13-00 
a a 
(z.) 
. . 0-70 
14-79 
0-18 
(x.) General purpose 
. . 1-50 
1145 
1-35 
(:?/•) 
.. 140 
15-80 
0-20 
h-) 
.. 1-25 
12-00 
1-25 
Casings. (28, 29, 30.) 
The casing is a product made from the intestines of cattle, sheep, and 
pigs. As far as the technical processes are involved, these chiefly are 
bacteriological in character ; it is the purpose in the manufacture of casings 
to produce an article which will not readily decompose, and in order to do 
this with a material which obviously is of a readily putrescible nature it 
is necessary to promptly and adequately treat the portion of the intestines- 
which is utilized. 
