354 MISCELLANEOUS FARM SUBJECTS 



the necessary elements without any soil whatever, and also, that 

 plants do not grow in soils altogether deficient in water soluble ma- 

 terials, although only a small amount is needed. Fortunately, 

 processes are continually going on in the soil by which the com- 

 binations of the different elements are changed gradually so that 

 small amounts of water soluble salts are being formed from those 

 which are insoluble. This gradual change from one form to an- 

 other is the chief explanation of the increased fertility. (Bu. of 

 Soils B. 55; Tex. Ex. Sta. B. 126; F. B. 257; Iowa Col. B. 95; 

 Univ. Wis. B. 139.) 



SOIL FERTILITY. 



The efficiency of any soil is measured by its capacity to supply 

 plants with the several materials and conditions they require for 

 growth. These include food, water, heat, air, and support; and in 

 addition the soil must be free from various diseases and animal 

 enemies that, in spite of a proper supply of all the essential condi- 

 tions of growth, may still prevent productiveness. In proportion 

 as any particular soil supplies all these essential conditions in well- 

 balanced abundance, the largest growth of plants may be obtained. 

 Again, if these conditions are deficient or improperly balanced by 

 the shortage of one of their number, a lower or more simple type 

 of plant or a smaller growth will result. Difference in soil condi- 

 tions results in different kinds of plant growth. Thus, wheat is 

 grown on deep, fertile loam, and mosses and ferns on thin, rocky 

 slopes, truck crops are grown on dry, warm sand, and sphagnum or 

 sweet flag on mucky marshes. The great variety in plants is due 

 to the great variety of soil conditions. 



The soil is the greatest natural resource of the Nation. With 

 the exhaustion of coal and iron it will supply, if rightly used, not 

 only food and clothing as at present, but also fuel, light, power, 

 and structural materials now supplied to a greater or less extent 

 by these minerals. It produces now over $7,000,000,000 in products 

 annually, forming a basis of our industrial wealth and a large propor- 

 tion of the foreign exports, yet we are but now taking up the last of 

 the public lands available for cultivation and the country is still so 

 sparsely settled that only about a quarter of the land nominally in 

 farms is actually under cultivation. 



From these lands we are getting only a third or a half the 

 yield per acre obtained on the older soils of Europe, and within 

 the past fifty years we have seen in many individual farms the 

 productivity of our new soils decline more than in equal proportion 

 to the increase in productivity of European countries. The pop- 

 ulation of the country is rapidly increasing and the time has surely 

 come when we must face the situation an of when we should take an 

 account of stock and deliberate as to what should be done to in- 

 crease the returns from the land and yet leave the soil in better 

 condition for succeeding generations, "the soil is the one natural 

 resource which, if properly used, not only clothes and feeds us, 

 but improves with age and careful treatment for the continued 

 use of posterity. 



