14 CONTENTS. 



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 ani- 

 mal charcoal All arable soils possess the power of absorption, but in different 

 degrees 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 avail- 

 able 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 available to plants- 

 Action of air, weather, decaying organic matters and chemical means Distri- 

 bution 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 preparing the soil Rotation of crops ; its influ- 

 ence on the quality of the soil ; action of draining Plants do not receive their 

 food from a solution circulating in the soil ; examination of drain, lysimeter, 

 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 solu- 

 tions containing their food ; similar experiments with soil containing the food 

 in a physically fixed state Intimate connection of natural laws Average 

 crop ; necessary quantity of assimilable food in the soil for the production of 

 such ; importance of the extent of surface of the food in the soil ; the root sur- 

 faceQuantity of food for a given surface of roots necessary for a wheat or 

 rye crop Analysis of the soil of a field Difference between fertility and pro- 

 ductive power of a field Mode of estimating relative extent of root surfaces 

 Conversion of rye into wheat soil ; quantity of food necessary for the pur- 

 pose ; the plan impracticable Immobility in the soil of the food of plants ; ex- 

 perience in agriculture Real and ideal maximum production Conversion in 

 practice of the chemically fixed food into an available form Effect of a manure 

 depends upon the property of the soil Improper relative proportions of the 

 different elements of food in the soil : effect of this upon the different culti- 

 vated plants : means for restoring the proper relative proportions, . . 73 



CHAPTER HI. 



ACTION OP SOIL ON FOOD OF PLANTS IN MANURE. 



Manures : meaning of the term ; their action as food of plants and means for im- 

 proving the soil Effect on soils with different powers of absorption Each soil 

 possesses a definite power of absorption ; the distribution of the food of plants 

 in the soil is inversely to the power of absorption ; means of counteracting the 

 absorptive power Absorption number, notion of; comparison of in different 

 fields ; its importance in husbandry Soil saturated with food of plants ; its 

 comportment with water Quantity of food to saturate a soil A saturated 

 eoil not required for the growth of plants Manuring may be compared to the 

 application of earth saturated with food Importance of the uniform distribu- 

 tion of food in manures ; fresh and rotted stall manure ; compost ; importance 

 of powdered turf for the preparation of manure Quantity of food in tin- 



