The plant food in the soil 



47 



of iron coated with tin but perforated with many holes. 

 I did not take the weight of the leaves that fell in the 

 autumn. In the end I dried the soil once more, and got 

 the same 200 pounds that I started with, less about two 

 ounces. Therefore the 164 pounds of wood, bark and 

 root arose from the water alone." The experiment is 

 wonderfully good and shows how very little plant food 

 there is in the soil. The conclusion is not quite right, 

 however, although it was for many years accepted as 

 proof of an ancient belief, which you will find mentioned 

 in Kingsley's Westward Ho!, that all things arose from 

 water. It is now known that the last sentence should 

 read, "Therefore the 164 pounds of wood, bark and root 

 arose chiefly from the water and air, but a small part 

 came from the soil also." 



But to return to our experiment with Pots 1 and 2. 

 They had been kept moist before the mustard was sown. 

 Did this moisture have any effect on the soil? Take 

 two of the pots that have been kept dry and uncropped, 

 and two that have been kept moist and uncropped, also 

 one of dry uncropped subsoil and one of moist un- 

 cropped subsoil. Sow rye or mustard in each pot and 

 keep them all equally supplied with water. 



It is soon evident that the top soil is richer in plant 

 food than the subsoil, and the soil stored moist is rather 

 richer than that stored dry, although the diflerence 

 here is less marked. In an experiment in which the 

 soils were put up early in July and sown at the end of 

 September the weights of crops in grams obtained 

 were : — 



