Arizona Agricultural Experiment Station 559 



were reduced materially by .075 percent sodium carbonate. 

 The main purpose of this series of cultures was to determine the 

 percentage of alkali in this particular type of soil, but the ex- 

 periment was adapted to the study of the influence of other 

 conditions. With this percentage fixed and held constant 

 through the series, other conditions will be varied. Such 

 observations have been made on the influence of texture in 

 soils containing .2 of one percent and .15 of one percent of 

 sodium carbonate. A very strong black alkaline soil was se- 

 lected and mixed with sand and with clay in order to reduce the 

 alkalinity; then combinations of the two mixtures were made 

 so as to give one series of .2 of one percent and another of .15 

 of one percent sodium carbonate, the two series varying only 

 in texture. Sand greatly intensified the toxicity of the black 

 alkali, while clay (or muck in one series) largely neutralized 

 the effect of the alkali. Other similar series, in which the 

 original sodium carbonate is held constant but wholly or in 

 part neutralized by gypsum, aluminum sulphate, mineral and 

 organic acids, are planned. A few preliminary trials along 

 this line have shown some very interesting results which will 

 be carefully checked with larger series next winter. 



THE TEMPE DRAINAGE DITCH 



Monthly samples of water from the Tempe Drainage Ditch 

 have been collected and analyzed. The study has now extended 

 over a period of four years and shows interesting results. Since 

 January 1920, there has been very little change in the com- 

 position of the water. This may possibly be due to the long 

 period of drought through which we have just passed. Table 

 IV gives the composition of water for each month from July 

 1920, to July 1921. 



