24 WHEAT PRODUCTION IN NEW ZEALAND 
though the variations are not distinct. Consequently 
we should expect to find different methods of cultivation 
and different kinds of seed sown, but such is by no 
means the case, and here then is one reason for a 
declining industry. 
(ii) Use of Fertilisers—-No greater evidence of the 
operation of the law of diminishing returns can be found 
than that the problems of artificially fertilizing the land 
are claiming attention in many countries of the World. 
It is not within my purpose in this paper to indulge in 
the technicalities arising from the more detailed aspect 
of the subject. To the chemist and agriculturalist will 
be left the consideration of the compositions of various 
manures; but for the purposes of considering the whole 
economic view it is often incumbent upon the economist 
to enter the domains of the physical and natural sciences. 
Hence the few speculations made upon the advantages 
of fertilisers must not be looked upon as a treatment of 
the chemistry of the subject. 
Two methods of adding plant food to the soil are at 
once apparent.—(1) Direct: (2) Indirect. 
(1) Direct.—The greatest problem with which the 
farmer has to contend in this respect is the provision 
of suitable quantities of nitrogen in the soil. It is the 
superiority in this respect which the Russian black soils 
and the virgin soils of Canada and the United States 
enjoy that makes them the home of wheat growing. 
Zealand soils generally are not of a black free nature, 
but contain comparatively low proportions of nitrogen, 
and when farmers realise this, better prospects will be 
in view. For the production of wheat on the most 
efficient basis, the soil requires now in most countries, 
in addition to nitrogen, complete mineral manures 
containing phosphorus, calcium, and potassium. 
Naturally, manuring for wheat was for many years 
thought to be quite unnecessary in New Zealand, because 
of the residual fertility of the soil. When, afterwards, 
manuring was commenced, the English practice in the 
application of nitrogenous manures was copied, and was 
found to be non-effectual, or at least uneconomical. 
