658 STATE BOARD OF AGRICULTURE. 



the small grains and grasses retarded accumulation of soluble sub- 

 stances in the soil solution in the field soils, although not to such a 

 marked degree as occurred in the cultures. On the other hand, the cul- 

 tivated crops, corn and beans did not so markedly affect the concentra- 

 tion of the soil solution in the soil. The study of the effect of plant 

 growth on the concentration of the soil is being continued. In the 

 studies several crops are being grown on tlie various soil classes under 

 different rates of seeding and other conditions. 



THE EFFECT OF DIFFERENT CONDITIONS OF A. MOISTURE AND B. TEMPERATURE 

 ON THE RATE OF FORMATION OF SOLUBLE SALTS IN CROPPED AND VIRGIN SOILS. 



The differences in productivity between virgin and long cultivated soils 

 has been the subject of much investigation. Chemical analyses have 

 shown in some cases differences in the total as well as the easily soluble 

 mineral nutrients and difference in the organic matter content are some 

 times quite marked. It is admitted, however, that no method yet devised 

 furnishes a consistent measure of the productivity of soils. 



Many phases of the factors that effect the solubility of soil constitu- 

 ents have been investigated by Bouyoucos, the results of which appear 

 in another publication. 



The idea suggested itself to the writers that possibly there is some 

 difference in the rate of formation of soluble constituents in cropped 

 and virgin soils. In consequence experiments were undertaken to measure 

 the variations in the concentration of the soil solutions of such soils 

 under different conditions of moisture and temperature. 



For use in these experiments samples of soils in the vicinity of the 

 College were collected on the 22nd of March. An effort was made to 

 obtain soils which had been cropped for a long period of years with little 

 or no addition of manure or other fertilizing material, A sample of the 

 virgin soil from a line fence was also collected. The samples represent 

 the first six inches of soil. vSimilar samples were taken May 17th in 

 Lenawee county from soils whose productivity had been greatly decreased. 



A. MOISTURE. 



High Water Content. For these investigations 20 gram !?amples of 

 the soils from Ingham county were weighed into ordinary freezing point 

 tubes and 20 c.c. of distilled water added. After one hour the freezing 

 point depressijns were determined with a IJeckmann thermometer in 

 the usual manner. The tubes were then stoppered and stored in a con- 

 stant temperature chamber at 25 °C. Weekly the contents of the tubes 

 were thoroughly agitated by stirring and shaking and the tubes allowed 

 to stand unstoppered for a short time in order to permit the escape of 

 carbon dioxide which might have been formed and which if allowed to 

 remain might affect the freezing point depression. 



The freezing point lowerings of the soil solution and the calculated 

 parts per million of soluble salts after ten and thirty-day periods are 

 shown in table 24. 



