2. Increasing the Availability of Soil Constituents 



Most soils contain large enough quantities of the important plant food 

 elements for good crops for many years, but as a rule only a small propor- 

 tion of these elements is in available forms. This is especially true of potash 

 which is locked up in enormous quantities in most of our soils and subsoils. 



There are two distinct lines of treatment which may help bring inert 

 soil constituents into available forms, namely tillage and the use of indirect 

 fertilizers. 



Tillage. Thorough tUlage should be mentioned first. It is within the 

 reach of all. Deeper plowing and more careful harrowing, more perfect pul- 

 verization of the soil for the production of a better seed-bed, and better care 

 of the crop while growing mean that the plant's needs will be more largely 

 met by the soil itself, for all these measures favor changes which render 

 naturally inactive soil constituents more available, and the amount of such 

 constituents in most soils is relatively large. 



Indirect Fertilizers. There are a number of materials, some of them 

 not in themselves usually important as direct sources of plant food and 

 others which are of value as direct sources of plant food, which exercise an 

 indirect effect upon the soil favorable to an increase in the availability of 

 some of its constituents. Among the more important of these may be men- 

 tioned lime in its different forms, land plaster, common salt, soda ash, 

 nitrate of soda and acid phosphate. Under existing conditions it is a matter 

 of the greatest importance that we consider to what extent the use of these 

 materials may bring inert soil constituents within the reach of the plant. 



(a) Lime 

 Lime is without doubt one of the most important of the indirect ferti- 

 lizers. It sweetens sour soils, promotes decay of organic matter, hastens the 

 availability of the plant food such matter contains, and increases the activ- 

 ity of beneficial soil organisms; it improves the physical condition of heavy 

 soils, and it is usually asserted that it helps make the naturally inert potash 

 of the soil more available. To what extent it will do this seems, however, 

 to be a question, and the experiments in this station indicate that in the 

 lighter and medium soils at least lime does not by any means take the place 

 of potash application. 



(b) Land Plaster 



Authorities have usually claimed that land plaster as well as lime in- 

 creases the availability of soil potash, but experiments in this station 

 indicate that its activity in that direction is not materially greater than that 

 of lime. The use of plaster cannot render application of potash unnecessary. 



(c) Common Salt 



It is claimed in some quarters for this material also that it will increase 

 the availability of the soil potash. It is probably worth trying for that pur- 

 pose. This station has no direct evidence bearing upon this question. It is 

 pointed out, however, that the chlorine which is a constituent of common 

 salt will undoubtedly increase the loss of lime from the soil, and the writer 

 believes that it may also exert an unfavorable influence upon the quality of 

 potatoes and perhaps render plants more susceptible to frost injury and 

 winterkiUing. 



(d) Soda Ash 



Soda ash may help sweeten a sour soil and may possibly somewhat de- 

 crease the necessity for the addition of potash, but the supply is small and 

 the price high. 



