CHLOROPHYLL AND ENERGY 217 



the community, they become less convincing when the facts 

 are considered more closely. 



It cannot be denied that atmospheric conditions are an 

 agent of destruction of the soil, but they are also, as pedology 

 shows, an agent of construction. If they had had no action, 

 we should find nearly everywhere the matrix intact, without the 

 slightest trace of cultivable soil. Atmospheric agents have made 

 all our soils and are still doing so. We are therefore obliged 

 to conclude, since soil exists, that the rate of destruction 

 is lower than the rate of construction. We alone are to 

 blame for this destruction that the neo-Malthusians adduce 

 to support their argument; we have ill-treated the soil, 

 and this leads us to examine one of the great errors of the 

 economists. 



The less work we had to do in cultivating the soil, the 

 greater would be its productivity. The ideal, which could 

 hardly be carried further, would be the practice of the 

 Canadian large farmer who goes out in the spring to plough 

 and sow immense fields of wheat to which he will not return 

 until harvest time. He reaps and threshes the wheat with a 

 combine harvester, taking away only the grain. In the 

 following spring he will return to repeat the process. This 

 extensive cultivation produces 4 to 5 cwt. per acre. 



At the opposite extreme is intensive cultivation, which 

 produces ten times more. For example, taking the yield of a 

 Dutch field as a basis, in 1939 only 11 per cent of that yield 

 was obtained in the United States, 30 per cent in France and 

 52 per cent in Germany. 



The soil represents a mass of elements of which only a 

 very small part can serve for the nutrition of the plant; a 

 relatively large accumulation will occur in the stem and 

 especially in the seed. At harvest time the field will lose some 

 of its wealth removed in the grain. In extensive cultivation 

 this is not replaced and the field becomes the poorer. 

 Inevitably, the yield progressively diminishes. 



In intensive cultivation, on the other hand, fertiUzers are 

 used as well as farmyard manure, which is so important for 



