42 



soil that the plant is feeding on." Professor C. G. Hopkins, in a 

 lecture given at Cornell last July, refers to the above quotation 

 and states that because of proven "uncompensated loss by leach- 

 ing of the upper soil in all normal humid sections, we dare not 

 base our definite plans for systems of permanent agriculture upon 

 a theory that by the rise of capillary water plant food is brought 

 from the lower subsoils sufficient to meet the needs of large crops 

 and to maintain the fertility of the surface soil in all places and 

 for all time." 



Professor Hopkins further says : " One dollar taken from loo 

 dollars leaves -not lOO dollars, but only 99 dollars. This is a 

 scientific fact which no theory or hypothesis can nullify. Like- 

 wise when a crop removes 20 pounds of phosphorus from the 

 soil it leaves that soil 20 pounds poorer in phosphorus than before 

 the crop was grown. The rotation of crops or the application of 

 salt or some other stimulant may liberate another 20 pounds of 

 phosphorus from the soil and thus enable us to grow another 

 crop the next year, and possibly this may be repeated for several 

 or many years, but meanwhile the total supply of phosphorus in 

 the soil is growing smaller and smaller year by year, until ulti- 

 mately neither crop rotation nor soil stimulants can liberate suf- 

 ficient phosphorus from the remaining meager supply to meet the 

 needs of profitable crops. It is certainly safe teaching and safe 

 practice to return to the soil as much or more than we remove 

 of such plant-food elements as are contained in the soil in limited 

 amounts when measured by the actual requirements of large crops 

 during one lifetime." 



The following extracts from President Roosevelt's recent mes- 

 sage to Congress are of interest : 



(i) " There are, of course, two kinds of natural resources. One 

 is the kind which can only be used as part of a process of ex- 

 haustion ; this is true of mines, natural oil and gas wells, and the 

 like. The other, and of course ultimately by far the most im- 

 portant, includes the resources which can be improved in the proc- 

 ess of wise use ; the soil, the rivers, and the forests come under 

 this head." 



(2) "There are small sections of our own country, in the east 



