368 STATE HORTICULTURAL SOCIETY. 



to it of the ash constituents of the plants that grew upon it. These 

 latter, the hydrous double silicates, are of the utmost importance to 

 the fertility of the soil, as in them really resides the power of holding 

 and storing up for future use the substances for the lack of which a 

 soil is wholly sterile. 



In all discussions of agricultural problems relating to mineral fer- 

 tilizers, but three substances need be considered : Potash, phosphoric 

 acid and available nitrogen. Our soils, as a result of careful investi- 

 gation, published in bulletin No. 6 of the Missouri Experiment Station, 

 contain, when perfectly dry ( dust-dry, i. e., with about 2.5 % of water ), 

 the following amounts of these in pounds to the acre: 



One acre contains in pounds in 



a. b. c. d. 



Water 79497 97980 166980 181500 



Potash 60853 59653 - 50094 21054 



Phosphoric acid 2541 2662 2178 726 



Nitrogen 4840 2299 726 not de- 

 Carbon 58927 27709 15972 termined 



a. First 10 inches, b. Second 10 inches. 



c. At depth of 3 feet in 10 inches, d. At depth of 12 feet in 10 inches. 

 One cubic foot of air-dried soil weighs about 100 pounds, and will retain, 

 when moistened, from 35 to 60— even 80— pounds of water. 



It is seen vast quantities of plant-food are stored up in our soils, 

 which if judged by chemieal analysis alone would have to be pro- 

 nounced as extremely fertile; yet it is well known that their fertility 

 at the present day is but moderate, and certainly much less than it 

 was 50 or 30 or even 20 years ago, and that chemistry as a means for 

 estimating the quality of a soil must tell us more than merely its 

 composition. This is owing to certain properties of the soil regarding 

 the absorption of plant-food, and the manner in which plants derive 

 from it their essential mineral constituents. 



Properties. — When it was first discovered that chemical analysis 

 was not in every instance a trustworthy guide by which to judge the 

 fertility of the soil, the search for the causes of this apparently excep- 

 tional conduct soon made it clear that the greater or less solubility of 

 the potash and phosphoric acid compounds of the soil must contain 

 the key to the solution of the difficulty ; for it stands to reason that 

 such compounds, if perfectly insoluble, could furnish to a plant no 

 nutriment whatever, and might as well be looked upon as altogether 

 absent. It is, therefore, not so much the existence of potash and phos- 

 phoric acid in the soil, but the manner in which it exists, or as it is 

 sometimes called, its assimilable form, that renders the latter produc- 

 tive. If chemistry by a mere soil analysis cannot enlighten the farmer 

 about the fertility of his land, a solution of the soil by leaching it out 



