24 



SCIENCE 



[N. S. Vol. LII. No. 1332 



therefore, is of fundamental importanee in 

 soil fertility. Unfortunately, limestone is 

 easily soluble in carbonated water, and of all 

 soil constituents probably is most readily lost 

 in tbe drainage water. Humid soils, as a rule, 

 are, therefore, deficient in this essential con- 

 stituent, and the first principle of soil fertility 

 is that limestone must be added to those soils 

 in which it is not already present. The lime- 

 stone is added primarily for the purpose of 

 creating conditions favorable to the growth of 

 the necessary legume crops, although it also 

 has a markedly favorable action in increasing 

 the yields of the cereal crops in the rotation. 

 There are various forms and kinds of lime- 

 stone materials available for use, but the work 

 of Dr. Hopkins has clearly demonstrated that 

 the most economic form to use is the finely 

 ground natural limestone — the normal material 

 occurring in the soil. The abundance of data 

 obtained by him on the various experimental 

 fields for the use of finely ground limestone, 

 particularly in southern Illinois, furnish now 

 the best infoi-mation the world affords regard- 

 ing the great benefit from the use of lime- 

 stone for the production of common farm 

 crops. The addition of limestone to the soil 

 not only corrects the acid conditions but also 

 provides the necessary calcium and magnesium 

 as planit foods. 



In most normal soils, such as the brown silt 

 loam, of the com belt, potassium occurs in the 

 soil in such large quantities that it will last 

 for the maximum production of crops for 

 indefinite periods of time and so, in the case 

 of potassium, the problem of the farmer is not 

 one of addition to such soils, but is one of 

 liberation from the insoluble compounds con- 

 tained in soil. A normal soil, well supplied 

 with fresh decomposing organic matter as pro- 

 vided in the grain or livestock system of farm- 

 ing, will provide sufiicient potassium to meet 

 the requirements of crops for this element; and 

 the experimental results, obtained from " the 

 various experimental fields for addition of 

 potassium, have shown clearly that it not only 

 does not pay for itseK, when used on such 

 soils, but gives little actual increased yield. 

 There are certain abnormal types of soil on 



which potassium is absolutely essential. Such 

 soils are peaty soils and soils deficient in or- 

 ganic matter. On peaty soils, potassium is the 

 limiting element of plant food and is often the 

 limiting factor of crop production. The addi- 

 tion of potassium, therefore, to such soils is an 

 absolute necessity. On soils deficient in or- 

 ganic matter, such as many of those occurring 

 in southern Illinois, potassium may be used 

 with profitable results until the soil has been 

 built up in its organic matter content. 



On normal soils, phosphorus is frequently 

 the limiting element of crop production. 

 There are various forms of phosphorus avail- 

 able for use such as barnyard manure, steamed 

 bone meal, basic slag, acid phosphate and raw 

 rock phosphate. Of the various forms avail- 

 able, the abundant experimental data, ob- 

 tained from the experimental fields main- 

 tained by the university, prove conclusively 

 that the finely ground raw rock phosphate may 

 be used with considerable profit and, for eco- 

 nomic reasons, this form of phosphorus is re- 

 garded as the most desirable form to use 

 although there may be special conditions 

 under which some of the either forms may be 

 used. 



There are two well-defined types of farm- 

 ing occurring in Illinois. These are the grain 

 system of farming and the livestock system of 

 farming. Both of these are perfectly legiti- 

 mate, proper, necessary and profitable systems 

 of farming, and it is possible and feasible to 

 provide means whereby the fertility of the soil 

 may be maintained on a permanent and profit- 

 able basis in either case. Both types of farm- 

 ing are absolutely necessary and essential to 

 the development of the highest stage of civili- 

 zation, for as long as man demands bread, 

 butter, meat and milk, and until we are will- 

 ing that our standard of living shall be low- 

 ered, both of these types of farming must ex- 

 ist. It is essential, therefore, that provision 

 be made whereby the fertility of the soil may 

 be maintained in order that grain and live- 

 stock farming may become permanent insti- 

 tutions in the land. The Illinois system of 

 permanent soil fertility recognizes this fact, 

 and makes provisions for the maintenance of 



