508 University of California Publications in Agricultural Sciences [Vol. 1 



matter in the treated as against those of the nntreated pots. 

 This is strikingly so for both the straw and tlie grain yield, but 

 is most consistently and undeniably apparent in the latter. The 

 root yields in most of the treated pots are also superior to those 

 obtained in the untreated pots, and duplicate cultures show 

 better agreement in that respect than do the straw and the 

 grain yields. The grain produced was in all cases well filled and 

 normal in appearance. In brief, we find that the second crop 

 on the soil treated with CuSO^, despite the doubling of the 

 CUSO4 application, shows as markedly, and perhaps even more 

 markedly, the stimulating effect of the salt under consideration 

 to barley grown on greenhouse soil. AVhile in detail the results 

 of the second crop differ from those of the first crop, they appear 

 to confirm the latter in general. The average yields of dry 

 matter are greater with all treatments than they are in the 

 untreated pots. This strikingly stimulating effect of CuSO^ on 

 barley under the conditions named in concentrations reaching 

 a maximum of 0.3 per cent CuSO^, based on the dry weight of 

 the soil, is as astounding as it is interesting, and it would appear 

 to lend little support to the idea of the toxicity of CuSO^ in 

 relatively small amounts to crops grown on field soils. This 

 phase of the subject will, however, receive more attention below. 



Third Crop 

 Grown under more propitious weather conditions, as ex- 

 plained above, the third ci'op in the CUSO4 series on the green- 

 house soil yielded throughout much larger amounts of dry 

 matter tlian the second crop, though not such large amounts as 

 the first crop. Again, we note the general stimulating effect of 

 CuSO^ to the production of dry matter in barley plants. This 

 time, it should be observed, the stimulating effect was not mani- 

 fest throughout the treated portion of the series, as it was in 

 the first two crops. Thus four of the CUSO4 concentrations 

 employed, namely, 600 p. p. m., 1600 p. p. m., 2400 p. p. m., and 

 2600 p. p. m., depressed the yield of barley if average yields of 

 duplicate pots are considered. In most cases, however, such 

 depression of yield is easily within the experimental error and 

 therefore may be without significance. This is especially so 



