112 WHEAT PRODUCTION IN NEW ZEALAND 
general trend of the average are exactly the opposite 
to these movements in yield per acre. This confirms the 
law of diminishing returns, which states that after a 
certain stage has been reached fresh additions of capital 
and labour to land do not yield corresponding returns. A 
modification of the law states that as the margin of 
cultivation extends and more land is brought under 
cultivation, the return per unit decreases. But the law 
of diminishing returns does not fully account for these 
movements in yield per acre. For, in the first place, the 
persistent decline of the yield during the ‘‘eighties’’ 
cannot be the result of soil exhaustion, nor of the intro- 
duction of inferior soils, since, as far as can be gathered, 
wheat production did not extend to these on a large 
scale. Secondly, the remarkable rise of 10 bushels per 
acre in the yield in the decade after 1895 at once suggests 
that more scientific methods of culture were introduced. 
These graphs showing comparisons in yield per acre and 
acreage for Canterbury and Otago individually, and for 
New Zealand as a whole, are full of suggestion and 
conclusively support the view that mixed farming is 
the most successful type for the wheat producing area 
of New Zealand. 
I have said that the change in agriculture since 
the ‘‘eighties’’ has been in both structure and technique. 
Structural changes have been brought about by the 
conversion of the large agricultural estate into a com- 
paratively small farm where both agriculture and 
pastoral pursuits are followed. The introduction of 
intensive cultivation in contrast to the unscientific 
methods of cropping practised on the large estate has 
fundamentally altered the technique of agriculture. It 
has been demonstrated that during the period of large 
scale production wheat growing was pursued extensively 
with little respect to the methods of cultivation and the 
distribution of energy over the field of production. This 
