1917] Forbes: Irrigation Effects of Copper Compounds Upon Crops 431 



Sample 

 No. 



3674 Tops of wheat and barley irrigated 

 3676 with water averaging 20 p.p.m. cop- 

 per 



Tops of beans, berseem, peas, onions, 

 lettuce, beets, radishes, corn, avas, 

 barley, and wheat irrigated with 

 water averaging 20 p.p.m. copper .... 



3690 Roots of same (washed in 4 per cent 

 HCl) 



30.70 



.000400 13.00 



27.20 .000751 27.60 



8.30 .000750 90.00 



In brief, even when relatively large amounts of water contain- 

 ing excessive quantities of soluble copper were applied and the 

 experiments so arranged that all of the copper remained in the 

 limited volumes of soil employed, no general injury to the plants 

 was observed, although apparently slight stimulation occurred in 

 some cases. Prolonged irrigation with such solutions would be 

 required to saturate the soil to a depth sufficient to seriously 

 injure plants grown in it. 



\ I 



I' 



Fig. 6. — Wheat and barley irrigated (C) with copper solutions filtered 

 through soil, and (W) with well water. Both shoAV stimulated growth with 

 copper. 



