40 THE SHADOW OF THE WORLD’S FUTURE
enormously altered, as some persons have somewhat
speculatively supposed, but it has recently been shown
that greatly increased yields are at least temporarily
attainable with cereals by transplanting. The increased
 yields are due to the greater root-development
thus obtained. The use of carbon dioxide has also led
to higher yields. We see, therefore, that improved
agricultural technique may yet yield surprising results.
Whether on a large scale such results are readily
obtainable or not, and whether it is possible to increase
yields three- and four-fold permanently or not, it is
perhaps too early to say. In any case these results,
while they relieve the outlook for the immediate
future, do not warrant any disregard for the outlook
resulting from population-increase.
It may here be noted that China, which has at any
rate till recently produced probably the highest yields,
has for many centuries used human waste. Experts
have stated that before long this will be a feature of
all agriculture: world-economics will, it is alleged,
make it necessary. There is reason to believe that, in
human affairs, waste of material and of effort will
continually diminish.
One is reminded also, in this connection, that the
extent of the possible use of fertilisers is a factor
of great moment. In South Australia, for example,
wheat-growing was unprofitable until superphosphates
were used; and as soon as they were used the economic
position was completely altered for the better. Before
passing on, however, to consider the light which the
use of manures throws on the world’s possibilities of
population, some consideration may be given to the
magnitude of the production of artificial fertilisers.
Statistics are collected regarding these by the International
 Institute of Agriculture at Rome. For 1920
the production in millions of metric tons—2204-6 Ibs.
—was as follows sem