CONTEXTS. 



CHAPTER ll.—conthiHcd. 



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 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, lysimeter, spring and 

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

 spring water contains volatile fatty acids ; amoimt 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 then- 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 natm-al laws — Average crop ; necessary 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 lye crop — 

 Analysis of the soil of a field — Difference 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 purpose ; the plan impracticable — Immobility in the soil of the food 

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

 tion — 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 cultivated plants : means for restor- 

 ing the proper relative proportions .... page G2 



CHAPTER III. 



ACTION OF SOIL ON FOOD OF PLANTS IN MANURE. 



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

 for improving the soil — Effect on soils with diflerent powers of ab- 

 soi-ption — Each soil possesses a definite power of absorption; the dis- 

 tribution 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 — Quantitv of food to saturate a soil — A saturated soil not 



