Lecture 7 



155 



Potassium Nutrition 



of crop growth ; granted that these requirements would 

 not necessarily imply the maintenance of soil solution 

 concentrations as high as those found at the beginning 

 of crop growth. 



We know from nutrient solution experiments of 

 the kind already described that the potassium required 

 by plants can be furnished from solutions in which 

 the potassium level does not exceed a few parts per 



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2 HOURS 



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10 20 30 40 50 



KBr CONCENTRATION OF EXTERNAL SOLUTION IN MIUEQUIV. PER UTER 



Textfigure 41, — Absorption of K by excised roots of young 

 barley plants as influenced by concentration of potassium in the 

 external solution. (From Hoagland and Broyer). 



million of solution, provided the concentration is prop- 

 erly maintained by flowing solutions, or by making 

 accessible to plant roots large volumes of stirred solu- 

 tion. From a dilute nutrient solution plants can absorb 

 more potassium relative to concentration than from 

 one of higher concentration. Experiments with tomato 

 plants have indicated that a flowing solution contain- 

 ing not more than five parts per million of potassium 

 suffices for good plant growth, at least in the vegeta- 



