Analysis of Soil and Its Relation to Plants 11 



the moisture from the seasonable showers, and admits 

 into its porous surface atmospheric air, thus suppljdng 

 necessary requisites for seed germination and plant- 

 growth. 



Soil analysis. — The chemist can tell us, through the 

 anah'sis of the soil, what elements it contains and how 

 much of each is present, but he cannot tell whether 

 these elements are available as plant -food. He cannot, 

 therefore, learn through the analysis what elements 

 must be supplied to any particular soil to increase plant- 

 production. Soil analysis is especially serviceable in its 

 negative results. If analysis shows the absence of any 

 one of the three essential elements, we know that it 

 must be supplied to render plant-growth possible. 



In an excellent bulletin (No. 94, New Series) of the 

 New York State Experiment Station, Dr. L. L. Van 

 Slyke, discussing the amount of plant-food in soil, says: 



"The amount of plant-food, even in a fertile soil, is 

 comparatively small. One thousand pounds of a good 

 soil may contain : 



Phosphoric acid H pounds 



Nitrogen H pounds 



Potash 2 pounds 



"Some soils may contain larger quantities than these. 

 But when we consider the total amount of plant -food 

 in one acre of soil, the amounts appear large." 



While the weight of soil in an acre of different kinds 

 of land varies, w^e may take the average weight of dry 

 soil in one acre, to the depth of nine inches, as approxi- 

 mating about 3,000,000 to 3,500,000 pounds. One acre 



