126 



Indiana University Studies 



There are at least ten chemical elements essential to the life 

 and growth of plants: oxygen, carbon, hydrogen, potassium, 

 magnesium, calcium, iron, sulphur, phosphorus, nitrogen. The 

 question of soil fertility can in fact be narrowed down to onlj^ two 

 of these elements, since all the others can be obtained from the 

 air and almost any soil that can be called in any way normal. 

 These two are phosphorus and nitrogen. In some cases potassium 

 must be added, but such cases are the exception. Since the air 

 contains an inexhaustible supply of nitrogen and this by properly 

 controlling the acidity of the soil becomes available thru the 

 action of nitrifying bacteria, the problem of soil fertility is largely 

 a matter of securing lime or limestone and phosphorus-bearing 

 compounds. In the few cases where the element potassium is 

 necessary, it can usually be obtained by treating the soil with 

 gypsum. Since nearly all soils contain more or less clay or waste 

 from feldspathic rocks and this contains the necessary potassium, 

 the calcium of the gypsum will slowl}^ replace the potassium in 

 the clay, giving rise to potassium sulphate from which the potas- 

 sium is available for the plants. 



The farmer of Indiana should no longer waste his earnings on 

 prepared fertilizers. It is time that he learn what is necessar}^ 

 in a fertilizer and prepare it himself for the soil on which it is to 

 be used. Prepared fertilizers must contain the necessary ele- 

 ments for a number of different soils, and thus the farmer who 

 purchases them must often purchase a large amount of material 

 which cannot possibl}^ be of any use on his particular soil. An 

 attempt should be made to educate the farmer to a point where 

 he will be able to determine what fertilizers his soils need and from 

 this knowledge bu}^ the raw materials and mix his own fertilizers. 

 The State of New York maintains a bureau of soils for the test- 

 ing of the soils of the State, and smy farmer who cares to submit a 

 sample of his soil can have it tested free of charge. With the 

 analysis he also receives advice as to the kind and amount of 

 fertilizer to use in the treatment of his land. This State could 

 find no more effective means of helping her agricultural popula- 

 tion than by maintaining a bureau where free analysis and 

 advice could be obtained. This idea has lateh^ been taken up 

 by a number of States, and in the future every large common- 

 wealth will furnish free of charge all the available scientific aid 

 possible. 



The physical effects of the use of ground Umestone on 

 different soils are very peculiar. When the ground limestone is 



