218 LIGHT, VEGETATION AND CHLOROPHYLL 



the renewal of humus. ^ The soil, far from becoming impov- 

 erished, improves from year to year and the yields steadily 

 increase. Obviously tliis increase is not unlimited and the 

 time comes when fertihzers, used even with the best technique 

 of soil science, cannot give better results or, more precisely, 

 do not pay, because their cost is no longer reimbursed by a 

 higher yield. Are there any fields where this point has really 

 been reached? Probably not, and the apparent exceptions 

 merely show evidence of a bad use of fertilizers. 



From the point of view of the land, there is no doubt 

 that intensive cultivation is much more advantageous than 

 extensive cultivation, particularly because it guarantees the 

 future instead of compromising it. But would the farmer give 

 the same reply? 



Surprising as it may seem at first sight, he does. With 

 approximately the same work, a Dutch agricultural family 

 obtains from its smaller acreage the same return as an 

 American family. In comparison, the French family hardly 

 obtains 57 per cent and the German 72 per cent; nevertheless 

 the French and German family have more land at their disposal 

 than the Dutch. This reminds us of what the old agricultural 

 economists used to say — that it was more profitable to double 

 the depth of one's field than to double its area. 



On 1,000 acres ten workers are employed in the United 

 States and ninety in Holland, but the Dutch worker gains as 

 much by cultivating his 11 acres as the American with his 

 100 acres. This indicates that the problem is not so much one 

 of over-population in the world as of bad distribution. 



We arrive at the conclusion that the cultivated land is 

 giving much less than its potential yield and that it would be 

 capable of nourishing far more people. Its area could also 

 be extended without much difficulty, perhaps doubled or even 

 trebled. In some depopulated districts, many fields remain 

 unploughed for so long that they can no longer be distinguished 



iThe humus soon diminishes in the soil when it is not suppHed with 

 manure. The general introduction of tractors causes an unforeseen 

 disequilibrium the importance of which should not be underestimated. 



