1917] Forbes: Irrigation Effects of Copper Compounds Upon Crops 445 



Two assembled samples of corn, radish, wheat, vetch and 

 peas grown in soils containing 0.005 per cent and 0.05 per cent 

 of copper were, therefore, very thoroughly washed out, copper 

 determined, and nitrogen determined X ^Vx for protein. The 

 amount of copper required to saturate vegetable protein was 

 assumed at 11.7 per cent (1-4.655 per cent CuO) — the average 

 of figures given in Mann's Chemistry of the Proteids, page 305. 



(1) Roots grown in .005% Cu in soil 4739000 gm. 



Cu .0105% 0000498 



N. 2.26% = Protein 14.125% 0669400 



Cu required for saturation of protein 



.06694 gm. X 11.7% = .007832 gm. Cu for saturation 



.0000498 ^^^^ 

 Per cent saturated = Q/xys. o9 =.o3/% 



(2) Roots grown in .05% Cu in soil 3561000 gm. 



Cu .0322% 0001147 



N. 2.76%= Protein 17.25% 0614900 



Cu required for saturation of protein 



.06149 gm. X 11.7% = .007194 gm. Cu for saturation 



.0001147 -, ^^,^ 

 Per cent saturated =-———— =: 1.594% 



.00(194 



Per cent 

 saturation 

 Q Cu p. p.m. of protein 



toummary: jj.j. roots with copper 



(1) .005% Cu in soil 105 0.636 



(2) .05% Cu in soil 322 1.594 



Ratio (1) to (2) 3.07 2.51 



In hrief, 10 times as much copper in the soil resulted in 3 

 times as much copper in the entire root systems and 2.5 times 

 as much in the protein of these root systems. This latter in- 

 crease, however, is responsible for an increase in damage from 

 almost nothing to very severe. 



Further observations on the copper-protein saturation figure 

 in roots grown in soil containing copper, were made on wheat 

 and Canada peas, planted in pots containing soil mixed with 

 varying percentages of copper in the form of precipitated basic 

 carbonate. The pots contained 102 pounds of sandy loam, and 

 were irrigated in a uniform manner from time to time as water 

 was needed. Plantings were made January 3, 1916, and roots 

 harvested May 15. 



