CHAPTEE II. 



THE SOIL. 



The soil contains fhe food of plants — Soil and subsoil ; conversion of tlie 

 latter into tlie former — Power of the soil to withdraw the food of 

 plants from solution in pure and in carbonic acid water ; similar action of 

 charcoal ; process of surface attraction ; chemical decomposition often 

 accompanies this attraction of the food of plants in the soil ; general 

 resemblance of the soil in its action to animal charcoal — AH arable soils 

 possess the power of absor^^tion, but in different degi-ees — Mode of the 

 distribution of the food of plants in the soil ; chemically and physically 

 fixed condition of the food — Only the physically fixed are available to 

 plants, being made soluble by the roots — Power of the soil to nourish 

 plants; on what dependent — Comportment of an exhausted soil in 

 fallow — Means for making the chemically fixed elements of food avail- 

 able to plants — Action of air, weather, decaying organic matters and 

 chemical means — Distribution of phosphoric and silicic acids ; influence 

 of organic matters — Action of lime — Process of the absorption of food 

 from the soil by the extremities of the roots — Mechanical preparation of 

 the soil ; its influence on the growth of plants ; chemical means for pre- 

 paring the soil — Rotation of crops ; its influence on the quality of the 

 soil ; action of draining — Plants do not receive their food from a solu- 

 tion circulating in the soil ; examination of drain ; lysemeter, spring and 

 river water: bog water, food of plants contained in it; Briickenauer 

 spring water contains volatile fatty acids ; amount of food of plants in 

 natural waters dependent on the nature of the soil through which they 

 flow — Mud and bog earth as manure ; explanation of their action — 

 Manner in which plants take up their food from the soil ; experiments on 

 the growth of plants in solutions containing their food ; similar experi- 

 ments with soil containing the food in a physically fixed state — Intimate 

 connection of natui-al laws — Average crop ; necessaiy quantity of assimi- 

 lable food in the soil for the production of such ; importance of the ex- 

 tent of surface of the food in the soil ; the root surface — Quantity of 

 food for a given surface of roots necessary for a wheat or rye crop — 

 Analysis of the soil of a field — Diff'erence between fertility and produc- 

 tive power of a field — Mode of estimating relative extent of root sur- 

 faces — Conversion of rye into wheat soil ; quantity of food necessary for 

 the pui-pose ; the plan impracticable — Immobility in the soil of the food 

 of plants ; experience in agriculture — Real and ideal maximum produc- 



