SECTION M.— AGRICULTURE. 



THE RELATION BETWEEN 

 CULTIVATED AREA AND POPULATION. 



ADDRESS BY 



SIR DANIEL HALL, K.C.B., LL.D., F.R.S., 



PRESIDENT OF THE SECTION. 



Recent considerations of the problem of the capacity of the world to 

 continue to feed its growing population appear to have begun with the 

 late Sir William Crookes' address as President of this Association when 

 he discussed the ultimate curtailment of the wheat supply through 

 exhaustion of the soil nitrogen. Crookes' views attracted little more 

 than academic attention at the time (1898), because the great tide 

 of wheat that was setting in from the newer countries still in the 

 process of exploitation was barely slackening ; moreover, Crookes had 

 neglected a factor then imperfectly appreciated — -the fact that land 

 under any of the conservative systems of farming adopted in the 

 old settled countries does not become exhausted. The recuperative 

 effects of the leguminous crops and the assimilation of nitrogen by soil 

 bacteria like Azotobacter, have maintained unimpaired the fertility of 

 European soils for perhaps thirty centuries of cultivation. Of course, 

 reckless exploitation, such as the continuous growth of wheat and maize 

 without any manuring, will eventually burn out the resources of even the 

 prairie soils of the Middle West, and there is evidence that some of the 

 long-cultivated Indian soils are losing fertility if only because dung and 

 other residues which should go back to the soil are being burnt as fuel or 

 sold away ; but, generally speaking, a soil will maintain itself indefinitely 

 at a certain level of production. Latterly in Europe that level has been 

 raised by the introduction of extraneous fertilisers. In his review Crookes 

 predicted the development of the synthetic processes of bringing nitrogen 

 into combination which are to-day rendering that prime element of 

 fertility so abundant and so cheap. But, though we no longer fear the 

 exhaustion of soils, of late years certain sociological considerations have 

 revived interest in the old thesis of Malthus. Over-population and 

 unemployment have become terrible realities in this and other countries ; 

 many States are finding themselves under pressure to maintain their 

 standard of living against the intrusion of neighbouring races propagating 

 recklessly down to the barest margin of sustenance. Again, various 

 studies of the course of prices of wheat have led to the conclusion that 

 before the war the real price was rising continuously, and that this 

 tendency is manifesting itself again, however much the true sequence of 

 prices has latterly been obscured by fluctuations of currency. These 

 considerations led Mr. Keynes to envisage the approach of scarcity : his 

 attitude is very much a return to Malthus. On the other hand, Sir William 



