1917] Forbes: Irrigation Effects of Copper Compounds Upon Crops 439 



cipitated carbonate was mixed (1) intimately and (2) in lumpy 

 condition. Results were as follows: 



In these instances it may be noted that toxic effects are asso- 

 ciated with higher copper content of roots of plants, rather than 

 with copper content of soils employed. 



As in other cultures it is observed that beans, though carry- 

 ing a higher copper content than corn, show less toxic effects — 

 a fact possibly to be explained by the higher protein content of 

 the plant with a consequently greater capacity for absorption 

 of copper before toxic effects appear. 



Pot and Plot Cultures 



In order to carry experimental cultures further towards field 

 conditions, cultures of wheat and corn in small plots of sandy 

 loam garden soil, 21/2 X 18 feet, were grown, copper in the form 

 of finely powdered sulphate having been thoroughly spaded in 

 four times to a depth of nine inches in the amounts shown in 

 table XXIII. The roots of these cultures were harvested and 

 examined as usual for copper. 



TABLE XXIII 

 Corn Grown in Garden Plots Containing Cu Applied as CuSOi (1914) 



* Probably resulting from roots spreading to copper soils. 



