Lecture 7 



— 165 — 



Potassium Nutrition 



of plant tissue produced. The percentage content of 

 a plant in calcium or magnesium, or both, will decrease 

 concomitantly with increase of potassium. Conversely, 

 an increase in the supply of absorbable calcium or 

 magnesium may tend to decrease the absorption of 

 potassium from a low potassium medium, although 



CO 



> 

 cr 

 o 



O 



o 

 o 



oc 



UJ 



a 

 uJ 



2 



2 50 500 750 



P.RM. K ADDED TO SOIL 



1000 



Textfigure 44. — With increasing additions of K salt to 

 this soil the calcium plus magnesium absorbed by tomato plants 

 decreased (per unit of tissue). Many chemical reactions occur 

 in the soil, but the effects on absorption of K and of Ca and _Mg 

 are considered as primaorily related to physiological interrelations 

 in ion absorption. Similar effects can be obtained in nutrient 

 culture solutions. (Hoagland and Martin, 1933). 



this effect is likely to be far less marked than the effect 

 of potassium on the absorption of calcium and magne- 

 sium.* The presence of ammonium ions in the medium 

 has the tendency to retard potassium absorption be- 



♦Within certain ranges of dilute solutions, calcium may 

 accelerate the absorption of potassium ions and the absorption 

 of anions as well, in short time studies on metabolically active 

 excised young barley roots, according to ViETS in this laboratory. 

 Another type of physiological effect than the one discussed above 

 is probably in operation under these special conditions. 



