1917] Forbes: Irrigation Effects of Copper Compounds Upon Crops 429 



reaching the plant roots. Radishes, beans, cantaloupes, cucum- 

 bers, lettuce, peas, beets, corn, berseem, avas, onions, barley, and 

 wheat were employed; corn, barley, and wheat being especially 

 successful under these conditions. All cultures were in pairs, 

 one of each pair being irrigated with solutions of basic carbonate 

 of copper in COo-water, and the check cultures with water only. 

 In all other particulars — original strength of plants, exposure 

 to light and air, and amount and time of watering — the con- 

 ditions were identical. 



These cultures were carried on in a greenhouse set aside for 

 the purpose. The experiment was begun in November and ended 

 the following March. The solutions of basic carbonate of copper 

 employed contained from to 55 p.p.m. of copper, averaging 

 about 20 parts, which is from 7 to 670 times as much as has 

 been observed in the waters of the Gila River from time to time. 



TABLE XVn 



Condition at Maturity of Cultures Irrigated with Copper Solutions, 

 AS Compared with those Irrigated with Water 



C, copper culture; W, check. 



Tops 

 C and W. 



Radishes 



Beans C greener 



Lettuce 



Peas 



Beets 



The 



Corn 



Berseem 



Stimulated ? C 

 showing stronger 



C stimulated, 

 earlier bloom 



same m appear- 

 ance and weight 



C and W. 

 About the same 



C and W. 

 About the same 



C and W. Aver- 

 aging the same 



Weighing the 

 same, but C ap- 

 pearing stronger 



C more advanced 

 in growth, but 

 not so heavy 



Roots 



The same, but in C 



roots were removed i 



in. from inner pot hole 



Equal; same number of 

 nodules; very local ef- 

 fect of Cu at pot hole 



The same except that in 

 C roots were dead f x ^ 

 in. under pot hole 



Both C and W having 

 abundant nodules. 



No apparent damage by 

 Cu 



Fewer in soil under pot 

 hole in C, otherwise 

 equal 



Equally developed, both 

 showing strong nodule 

 development. 



