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



Again, unlike the first crop on the adobe soil, the second crop 

 yielded no "Taiii- This of course cannot be attributed in anv 

 way to the effects of CuSO^, since the control pots behaved 

 in the respect noted like the treated ones. Presumably, unfavor- 

 able climatic conditions and the heavy nature of the soil may 

 have produced and influenced the result obtained. The root 

 yields, however, were very considerably larger in the second 

 than in the first crop, and fairly good agreement between dupli- 

 cate determinations was obtained. Considering the small total 

 yield of dry matter in roots, it is perhaps a very significant 

 stimulation to their development which CuSO^ exerts. 



Regarded then from the standpoint of the total dry matter 

 produced, there appears to be no question from the data in 

 table III& that CuSO^ can stimulate growth in the barley plant 

 on a clay adobe soil even when present at very considerable 

 concentrations. If only the dry matter of the above-ground 

 parts is considered, three exceptions to this rule in the whole 

 series can be found. In a general way, the results with CuSO^ 

 on the adobe soil confirm those obtained on the greenhouse soil 

 using the same salt. It may be repeated with advantage here 

 that even if such stimulating properties of CUSO4, which in our 

 opinion we have shown above to exist, are not allowed, our data 

 do not offer any support to the idea that in the ordinary quan- 

 tities in which copper may be introduced in agricultural soils it 

 is even likely to be toxic to grain plants. 



Copper Sulfate — Oakley Soil 

 Only one crop of barley was grown on the Oakley soil in 

 the tests with CuSO^. Since closing the experiment we have 

 regretted the fact that the Oakley soil was not cropped succes- 

 sively for two or three seasons after treatment, but at the time 

 of the experiment this was not deemed necessary. Table TV 

 gives the results obtained with the one crop in question. The 

 figures really do not tell the whole story, since the appearance 

 of the barley plants was far superior on the treated soils on 

 which they developed at all tlian it was on the untreated soil. 

 Nevertheless, the figures are striking enough to be used alone 



