0141737 



teristics, plant species and climatic variables. Irrigation 

 methods can also influence the relative toxicity of some elements. 

 Sprinkler irrigation can result in foliar absorption or adsorption 

 of minerals at levels detrimental to plant growth if the water 

 contains excessive levels of some constituents (Federal Water 

 Pollution Control Administration 1968). Ground application of the 

 same water may not produce any adverse effects due to soil 

 chemical and physical properties that may reduce some elements to 

 insoluble forms and adsorption of elements by soil constituents 

 with high cation exchange capacity. Helena Valley waters analyzed 

 by Soukup (1972) contained no levels above the more restrictive 

 irrigation criteria for all soils for arsenic, cadmium, lead and 

 zinc (Table 46) . 



Table 46. Irrigation water criteria for arsenic, cadmium, lead, 

 and zinc. 



Use As Cd Pb Zn Reference 



mg/L 



Irrigation 



All Soils 0.1 0.01 5 2 NRC 1972 



Irrigation 

 Fine Textured 

 Soils 2.0 0.05 10 10 NRC 1972 



The use of contaminated surface runoff, waters receiving in- 

 dustrial effluent or polluted ground water could result in waters 

 exceeding existing irrigation guidelines. 



137 



