CERTAIN EFFECTS UNDER IRRIGATION OF 

 COPPER COMPOUNDS UPON CROPS 



By R. H. FORBES 



Part I.- EXPERIMENTAL WORK 



INTRODUCTION 



The region to which the studies described in this publication 

 more particularly relate lies in southeastern Arizona in Greenlee 

 and Graham counties and consists, first, of the Clifton-Morenci 

 mining district and second, of the irrigated lands along the Gila 

 River from twenty-five to sixty miles below. The Clifton-Morenci 

 mining district is drained by Chase Creek into the San Francisco 

 River, which in turn empties into the Gila. From the Gila, be- 

 ginning at a point about twenty-five miles by channel below 

 Clifton, irrigating waters are withdrawn for the use of the rich 

 lands extending somewhat discontinuously from above San Jose 

 to Fort Thomas, a distance of thirty miles. For about forty 

 years, this up-stream mining district and the irrigated lands 

 below have developed together from small beginnings into large 

 industries. 



Beginning with the initiation of smelting operations on the 

 San Francisco River in 1882, comparatively small amounts of 

 mining detritus must have found their way into the irrigating 

 water-supply. Following the discovery, in 1893, of immense 

 deposits of low-grade sulphide ores in the district and the erec- 

 tion of concentrating plants to handle them, rapidly increasing 

 quantities of fine slimes were discharged into the stream-flow, 

 becoming noticeable in the irrigating waters of Graham County 

 about the year 1900. Following the observation of their pres- 

 ence, various crop failures were attributed from time to time to 

 the tailings, resulting finally in a request by the farmers of the 

 district to the writer, for an examination of the facts relating 

 to damage done by mining detritus to their irrigated crops. 



