Food jroni the Soil 1 55 



grows upon paste, or jam, arc all of similar nature, 

 and all produce alterations in the substance which 

 they attack. When we like the result of these 

 alterations, we call the process 'fermentation'; and 

 when we do not like it, we call it 'putrefaction'; but 

 both are substantially the same, for both are the result 

 of decomposition. Grape-juice, apple-juice, and wort, 

 are converted by these * ferments ' into wine, cider, 

 and beer respectively ; and another ferment again 

 alters wine yet further, and turns it into vinegar. 



It is these living organisms which bring about all 

 decay of animal or vegetable matter, whether in the 

 soil or elsewhere. 



Their work in the soil seems to go on chiefly in the 

 upper nine inches, and most rapidly when the weather 

 is warm and damp. 



The multitudes of leaves drawn in by worms, the 

 old roots of former crops, or green crops which have 

 been grown only that they may be ploughed in— all 

 are decayed, and so converted into food, of which the 

 next crop can avail itself 



As has been more than once remarked, all soils 

 contain more or less organic matter ; but unless the 

 amount is very large, as it is in the Russian Black 

 earth region, Manitoba, and elsewhere, not much of 

 the nitrates formed by its decay will be left in the 

 upper twenty-seven inches of the soil after a crop of 

 corn has been grown in it. Organic matter there will 

 still be, but decay is gradual, and nitrates take time to 

 form ; so the farmer must supply the want in one way 

 or other. 



In former days, till within the last centur}' in fact, 

 his way of doing so was simple. He merely ploughed 



