40 SUCCESSFUL FARMING 



sequent hastening of the impoverishment of the soil. Except in very 

 sandy soils, in the practice of bare fallowing of soils, and in the Southern 

 states where land is left without cover-crops, there is very little danger, 

 however, in this regard. 



Chemical Composition of Soils. The soil has long been an intricate 

 problem for the chemist. Many years of research have been spent in an 

 endeavor to determine through chemical analysis not only the composition 

 of the soil but its power to produce crops and its need for fertilizers. The 

 chemist has little difficulty in determining the absolute amounts of the 

 essential plant food constituents in the soil, although the process is rather 

 long, tedious and costly. Unfortunately, such analyses seldom indicate 

 the relative fertility of different soils, and tell us comparatively little as 

 to the present fertilizer needs of them. The chemist has also endeavored 

 to devise methods of analysis that will determine the amounts of avail- 

 able plant food present in the soil. For this he has used different solvents 

 of varying concentrations in an endeavor to imitate the plant in its ex- 

 traction of the elements from the soil. So far, however, such methods 

 have met with comparatively little success, and we are, therefore, obliged 

 to conclude that, as a rule, a chemical analysis of the soil is of very little 

 help to the farmer. This statement admits of certain exceptions. If the 

 analyst finds that the total potash or phosphorus content of a soil is very 

 small, it at once indicates that this soil is either immediately in need of 

 the deficient element or soon will become so. It is also true that, when 

 the physical conditions of the soil are good, the drainage satisfactory and 

 unusually large amounts of the essential elements are present, the soils 

 are, or may easily be made, productive without the addition of plant 

 food. 



The above statements should not be construed to mean that the 

 chemist should cease to put forth his best efforts in the solution of un- 

 solved soil problems; but in its present status, it is not worth while for 

 the farmer to ask for a complete chemical analysis of his soil, or to go to 

 the expense of having a commercial chemist make such an analysis for 

 him. Chemical analyses are useful and helpful to the scientist and soil 

 expert, and are to be encouraged as a help in the advancement of our 

 knowledge of soils. 



Availability Important. In the majority of cases it is important 

 that the farmer know how to increase the availability of plant food in 

 the soil. This question has been partly analyzed in the preceding topic 

 on solubility of soil minerals. In general, however, the farmer may 

 increase availability by deep plowing, thorough tillage, the incorporation 

 of organic matter and soil drainage. The best measure of soil fertility 

 or available plant food is the growth that plants make upon any particular 

 soil. Not only is the degree of growth an indication of fertility, but like- 

 wise the color of the plants, the manner of growth and the proportion of 

 vegetative parts to seeds or fruits are often indicative of the presence or 



