Oct.29, I92I Absorption of Copper jrofyi the Soil hy Potato Plants 287 



Table III. — Effect on potato tubers and vines of applications of sprays to soil 



a Rot found only on control tubers. 



These data show tliat the solution of copper sulphate had a very dis- 

 astrous effect on the growth and yield of the tubers. The only decayed 

 tubers found were obtained from the unsprayed plot. These results are 

 so few that they can be considered only as suggestive. 



vSUMMARY 



Potato plants grown in soil treated with insoluble copper compounds 

 contained more copper in the leaves than in the stems, while but little 

 copper was found in the roots. The tubers showed only traces of copper. 



When the soil was treated with the copper sulphate solution, the roots 

 were injured and the normal metabolism of the vines was disturbed. 

 The tubers from these vines were small and the vines stunted. The roots 

 of these plants held more copper than the leaves. 



The soluble copper sulphate added directly to the soil caused injury 

 to the plants, while the insoluble copper compounds of the sprays did 

 not. The excess lime of the Bordeaux spray did not reduce the amount 

 of copper absorbed by the plants compared with the plants grown on 

 the Pickering plot. 



Practically the same amounts of copper were found in all the soil 

 samples tested. Samples of soil from sprayed potato fields showed but 

 minute amounts of copper. 



