510 Vni'versity of California Publications in Agricultural Sciences [Vol. 1 



to start it for comparison with the greenhouse soil until one 

 crop had been obtained with the latter. 



First Crop 



We find in the case of the adobe soil the same unfortunate 

 disparity among the yields of duplicate pots which was noted 

 with the greenhouse soil. This disparity is of course the more 

 noticeable when much smaller absolute amounts are involved, as 

 in the present case. Despite all that, however, there appears 

 to be justification for the conclusion, based on the data in table 

 Illfl, that CuSO^ does exercise a stimulating action on the 

 growth of barley in adobe soil. Such stimulation is not apparent 

 throughout the whole series, as it is in the case of tlie green- 

 house soil, but it appears to exist in all concentrations of CuSO^ 

 employed up to 900 p. p. m. Concentrations in excess of the 

 latter seem to depress, definitely, the yield on the adobe soil. 

 But whether or not we admit the existence of a stimulating effect 

 by CuSO^ on the barley, based on the figures here studied, it 

 can scarcely be denied that CUSO4 is not toxic to barley in 

 the first crop grown on adobe soil until nearly 0.1 per cent 

 CuSO^ is present in the soil. Amounts of CUSO4 slightl.y less 

 than 0.1 per cent stimulate the growth of the barley significantly. 

 At concentrations of 0.15 per cent and 0.2 per cent CuSO^ no 

 growth is obtained at all, showing of course marked toxicity. 



Some interesting facts are brought to light in table Ilia with 

 respect to the relationships among straw, grain, and root yields 

 which obtain between treated and untreated soils and among 

 themselves in the case of the different concentrations of the 

 latter. In the first place, it will be noted that the grain yields 

 form an even larger percentage of the total dry matter of the 

 first crop on the adobe soil than they do in the second crop on 

 the greenhouse soil. In some cases, indeed, the average yield of 

 grain in duplicate pots exceeded the average yield of straw. In 

 nearly half the treatments, the grain yields were larger than 

 those of the control pots so that the stimulating effect of the 

 CUSO4 application, if allowed, applies to the grain jdelds as 

 well as to those of total dry matter. The root yields are pro- 



