FARM MANURES 347 



which manure improves the soil. There was a 

 time when the value of manure was thought to be 

 only or chiefly the value of the plant food it con- 

 tained. It was even said that since a ton of stable 

 manure contains but $2 to $4 worth of nitrogen, pot- 

 ash and phosphoric acid, that the same amount of 

 plant food could be obtained and applied more 

 cheaply in the form of a commercial fertiliser. This 

 is true ; but the conclusion must not be drawn that 

 manure might well be supplanted by commercial 

 fertilisers. From the chemist's point of view a ton 

 of manure may be worth but $2, because that is the 

 value of all the plant food in it. From the farmer's 

 point of view manure may be worth several times 

 that amount. The farmer knows that he cannot 

 buy $2 worth of artificial fertiliser that will give 

 the results on most soils that one ton of manure will. 

 This fact, which is realised by farmers everywhere, 

 has led to a very careful investigation of the ways in 

 which manure benefits the soil, aside from adding 

 the small amount of plant food it contains. These 

 supplementary benefits, which the chemist knows 

 notning of and does not consider in his estimates of 

 the value of different kinds of manures, are often 

 of far greater practical value in crop production 

 than the plant food that the manure contains. 



Manure Improves Texture of the Soil. The 

 chief value of manure, on many soils is not the plant 

 food it adds but its beneficial effect upon the tex- 

 ture of the soil. In the preceding chapter it was 

 shown that most farm soils, even those that are 

 unproductive and worn-out, contain large amounts 

 of plant food; and that the cause of the unpro- 

 ductiveness is more apt to be that the soil is in poor 

 condition, or bad heart, than that it is exhausted of 

 plant food. 



