THE CAMPBELL SYSTEM 



ture-saving mulch. From this time on, 

 the field must be cultivated after every 

 rain and often enough to prevent any 

 weeds from growing. It is then seeded 

 to winter wheat or left over for the fol- 

 lowing spring crop. It will thus be seen 

 that two decided benefits accrue from 

 Mr. Campbell's method of summer till- 

 age: (1) The storage of the rainfall of 

 part of the season. Experiments have 

 shown that with the loam soil and clay 

 sub-soils of the western prairies but little 

 moisture is lost by percolation. (2) By 

 maintaining a loose mulch on the surface 

 and so preserving the moisture under- 

 neath and by allowing the sunshine and 

 air to permeate into the ground the ac- 

 tivity of the beneficial soil-germs is en- 

 couraged. 



Regarding the possibilities of summer 

 culture in semi-arid States, Campbell 

 writes : 



155 



