1919 .] Wild and Speight—Limestones of Canterbury. 191 
connection is not out of place in this report if only in so far as the pre¬ 
sence of small percentages of phosphate has, under the circumstances, an 
important bearing on the question. It happens, moreover, that this matter 
has in times past received our individual attention.* 
In the first place, while phosphatic fertilizers have for a great many 
years been an essential to successful agriculture in Canterbury, the need 
for lime has apparently not been in the least acute ; at all events, farmers 
in general have managed very well without it. In the second place, at no 
time have cheap supplies of lime been available for agricultural purposes 
in this province. At the present time, however, whether the system of 
cropping so long practised is beginning to have its effect on a soil admittedly 
not rich in lime, or whether from other less obvious causes, signs are not 
wanting that lime is about to come into its own, and more farmers are 
to be found who have begun to use lime and have obtained pleasing 
results therefrom. Thus the Canterbury Agricultural College has used lime 
extensively during the last three or four years ; Mr. R. Macartney, of Tai 
Tapu, has informed us of gratifying results of its use on his farm at 
Methven ; and we have heard favourable reports from such widely scattered 
districts as Sefton, Dunsandel, and Ashburton. The demand so created 
should encourage the opening-up of new supplies, and we have no hesitation 
in stating that in both North and South Canterbury ample supplies are 
available in accessible localities, where the cost should certainly not be 
greater than that ruling in Southland—namely, 14s. per ton for ground 
limestone—where the preliminary difficulties of drying before grinding 
must be greater than in our district. 
In estimating the agricultural value of a sample of limestone it has 
been customary hitherto to insist on two factors—namely, purity and 
fineness of grinding. It is a fact, however, that the cost of pulverizing a 
sample is out of all proportion to the cost of merely crushing so that the 
whole will pass through a J in. or J in. mesh ; nevertheless, in this opera¬ 
tion of crushing much fine powder is produced, so that the whole of such 
a sample may be considered capable of giving immediate results as well as 
long-continued activity as a soil-improver.*)* If, then, a coarsely ground 
sample can be got much more cheaply than a pulverized one and be as 
effective in the long-run, the production of such a sample may prove accept¬ 
able to the Canterbury farmer. More of it can, of course, be had for the 
same outlay, which is important in view of the phosphate content of the 
rock, a point that we come to consider presently. The transport charges are 
not proportionately increased, since railage on lime is free for 100 miles. 
Reasons can also be put forward for urging a revision of the demand 
for a sample of limestone possessing high purity. Many Canterbury lime¬ 
stones in the more accessible localities are not markedly pure, though they 
have the advantage of being cheaply worked. Now, while the bulk of 
the impurity is sand, a proportion of it is phosphate, so that in some cases 
a dressing of limestone, 10 cwt. or so, would add to the soil as much 
phosphate as an application of 1 cwt. of fertilizer. It is not suggested 
that this small addition of phosphate would of itself produce an immediate 
* R. Speight, The Limestones of the Canterbury Province, Journ. Canterbury 
A. & P. Assn 1916 ; L. J. Wild, Some Soils of the South Island of New Zealand with 
Special Reference to their Lime Requirements, Journ. Agric. Sci., vol. 8, p. 154, 1917 ; 
L. J. Wild and J. G. Anderson, On the Absorption of Lime by Soils, Trans. N.Z. 
Inst, vol. 49, p. 466, 1917. 
t See, e.g., B. C. Aston, Two Notes on Limestone (quoting C. G. Hopkins), N.Z. 
Journ. of Agr., vol. 16, p. 162, 1918. 
