1917J Forbes: Irrigation Effects of Copper Compounds Upon Crops 417 



root systems. The acid-wash and soil-correction methods give 

 severely minimum results. The carbon dioxide wash used in the 

 majority of analyses is laborious but more satisfactory. 



Water Cultures (1907) 



Cultures of corn, beans, and squash were grown in University 

 of Arizona well-water containing 250 p. p.m. of soluble solids. 

 From 0.03 to 3.0 parts of copper as precipitated carbonate dis- 

 solved in carbon dioxide were used in making cultures and the 

 resulting growths of tops and roots were divided into the worst- 

 poisoned and least-poisoned portions, for determinations of 

 copper. 



Fig. 3. — Corn cultures, series 121-62, grown in University of Arizona 

 well water, containing from .03 to 3. parts per million of copper as basic 

 carbonate (Cu(0H)o.CuC03). 



Series Corn 121-62. — Grown in well water containing Cu as 

 Cu(OH).,.CuCO., as follows: check, 3.0, 1.0, 0.8, 0.5, 0.3, 0.1, 

 0.08, 0.05", and 0.03 p.p.m. Cu. December 1-February 27, 1907. 

 Series divided into two portions: 



a. Plants not badly poisoned ; roots growing ; tops showing 

 Cu etfects; 0.1, 0.08, o'.05, 0.03 cultures. (Nos. 3694, 3693.) 



h. Plants badlv poisoned; root growth arrested; tops living; 

 3.0, 1.0, 0.8, 0.5, aiid 0.3 cultures. (Nos. 3692, 3691.) 



Series Beans 121-66. — Grown in well water containing Cu 

 as Cu(OH),.CuCO.. as follows: check, 3.0, 1.0, 0.8, 0.5, 0.3, 0.1, 

 0.08, 0.05, 0.03 p.p.m. Cu. December 9-February 27, 1907. 

 Series divided into two portions : 



a. Least poisoned plants ; roots nearly normal, tops normal ; 

 0.3, 0.1, 0.08, 0.05, 0.03 cultures. (Nos. 3702, 3697.) 



