THE NATURE OF SOIL 25 



Fineness is Richness. The fineness of the soil 

 has a very important bearing upon its fertility. 

 Other things being equal, the finer a soil is, the 

 richer it is, because it contains more surface 

 for the roots to feed upon. The rootlets of 

 plants do not suck up particles of soil, as 

 Jethro Tull supposed, in his now famous 

 "Horse-hoeing Husbandry." They feed upon 

 the film water upon the outside of the soil 

 grains. This contains much plant food dis- 

 solved from the grains. The natural agencies 

 that dissolve -plant food from the soil water, air, 

 etc., act only on the outside of the particles. Hence 

 the more surface there is to the grains, the greater 

 is the "pasturage," or feeding area for the rootlets, 

 and the more rapid is the weathering. If a small 

 stone is broken into six pieces, the pieces have 

 several times more surface, in the aggregate, than 

 the unbroken stone. It has been calculated that 

 if every particle in one cubic foot of mellow soil 

 could nave all its surface spread out flat, the ag- 

 gregate surfaces of all these grains would cover 

 about one acre. 



The presence of small stones and pebbles in a 

 soil is beneficial, making it lighter, more porous, and 

 warmer. It would be a great calamity if all soils 

 contained no pebbles and larger pieces of rocks. 

 These are a store of plant food which is added to 

 the soil from year to year. Yet the farmer should 

 remember that, in general, fineness means richness. 

 If a soil is lumpy, because of lack of humus or 

 excessive moisture, its available feeding area is 

 greatly reduced. This matter is considered more 

 fully in succeeding chapters, where practical 

 methods of making a soil fine and mellow are de- 

 scribed. 



