206 



Soils that have been under wheat cultivation 

 for long periods are generally defective in the 

 following particulars : They lack soluble silica, 

 or flint in an available form, with which to 

 produce hard, glassy stems that are little 

 subject to "rust." Cultivated soils never contain 

 soluble flint in great abundance, and, after being 

 tilled some years, the quantity becomes still less. 

 It is not very difficult to accurately learn the 

 amount of silica which rain-water, as it falls on the 

 earth, will dissolve out of 1,000 grains of soil in the 

 course of eight or ten days. Hot water will dissolve 

 more than cold water ; and water charged with 

 carbonic acid, more than pure hot water. 



What elements of crops rain-water, at summer 

 heat, will render available to the plant out of ten 

 or twenty pounds of soil, in the course of three 

 months, is a point in agricultural science which 

 should be made the subject of numerous and 

 careful experiments. In this way, the capabilities 

 of different soils, and their adaptation to different 

 crops, may be tested in connection with practical 

 experiments in field-culture on the same kind of 

 earth. Few wheat-growers are aware how much 

 available silica an acre of good wheat demands to 

 prevent the plants having coarse, soft, and spongy 

 stems, which are anything but an indication of 

 healthy organization. 



In the Journal of the Royal Agricultural Society, 



