558 STATE BOARD OF AGRICULTURE. 



INTRODUCTION. 



Technical Bulletin No. 31. 



GEORGE J. nOUYOUCOS AND M. M. MCCOOL. 



In a former publication (1) the freezing point method was presented as 

 a new means of measuring tlie concentration of the soil solution directly 

 in the soil mass, at various moisture contents and under different ferti- 

 lizer treatments. The general results yielded by the method appeared on 

 the whole quite revolutionary and in some respects almost incredible. 

 With the desire to establish, as far as it was possible, the absolute 

 truthfulness of the method and consequently the reliability of the re- 

 sults, the general investigation was repeated a second time and greatly 

 extended. In the second investigation an attempt was made to be ex- 

 tremely critical both with the method and the results obtained. The 

 general method was somewhat modified and in certain essential details 

 greatly improved. The scope of the investigation was considerably en- 

 larged by employing a greater number of soils, which were obtained 

 from various parts of the country, and by applying to these soils a 

 greater number of treatments. 



It is a personal source of gratification to us now to state that the re- 

 sults obtained in the first investigation, the general conclusions drawn 

 therefrom, and the various explanations offered, are fully and entirely 

 confirmed and substantiated by these later improved, greatly extended 

 and more critical researches. We are now confidently convinced that 

 the freezing point method gives truthful and reliable results on the 

 freezing-point lowering of soils at various moisture contents and under 

 different fertilizer treatments. 



Since the appearance of the first paper already referred to, the freez- 

 ing point method has been applied in studying other problems besides 

 those already mentioned. Some of the problems investigated by this 

 method may be mentioned as follows: (a) Measuring the concentration 

 of the plant cell sap directly in the plant tissue (2), (b) Measuring bio- 

 logical actions directly in the soil (3), (c) Determining the nature of 

 acidity and lime requirement of soils (4). The experience gained from 

 these varied studies and the opportunity they offered to test out the 

 method have amply confirmed and greatly strengthened the above con- 

 viction. 



It is the object of the present bulletin, therefore, to present the addi- 

 tional data obtained by the freezing point method on the concentration 

 of the soil solution at various moisture contents and under various other 

 treatments, to compare these results with those of the first investigation, 



(1) Bouyoucos, G. and McCool, M. M. — The Freezing Point Method as a New Means of Determin- 

 ing the Concentration of the Soil Solution Directly in the Soil. Tech. Bui. 24, Mich. Exp. Stat., 1916, 



(2) Bouyoucos, G. and McCool, M. M. — Determination of Cell Sap Concentration by the Freezing 

 Point Method. Jour. Am. Soc. Agr., Vol. 8, No. 1, 1916. 



(3) Bouyoucos, G. — Measuring Biological Actions by the Freezing Point Method Directly in the 

 Soil, Science 44, 65-66, 1916. 



(4) Bouyoucos, G. — -The Freezing Point Method as a New Means of Determining the Nature of 

 Acidity and Lime Requirements of Soils. Tech. Bui. 27, Mich. Expt. Sta., 1916. 



