jan.6. I9I9 A.sh Absorption by Spinach 25 



the crops does not parallel high ash absorption, the best and poorest 

 plots having plants with low ash. 



Ash constituents fall into two groups: (i) those present in quantities 

 that show relatively little variation whatever be the chemicals added 

 to the soil — lime, magnesia, phosphorous pentoxid, sulphur trioxid, 

 manganous oxid, alumina, and ferric oxid; and (2) those which show 

 great fluctuations in the quantity present — silica, potash, and soda. 



In the first group the plants seemed to be able to get the required 

 quantity of constituents mentioned from the soil of all plots studied 

 whatever was offered in excess, and reached an equihbrium that was 

 little affected by the varying conditions. 



In the second group wide variations occur, sometimes with an increase 

 of the ions offered in excess, as in sodium chlorid and sodium nitrate, 

 sometimes by the absorption of something else, as increase in silica in 

 plots receiving calcium carbonate and acid phosphate. 



Manganous oxid is the only constituent regularly present in greater 

 proportion in the roots than in the tops. 



In some cases the high absorption of one constituent is accompanied 

 by the low absorption of another, and vice versa. Such reciprocal pairs 

 are silica and potash, soda and lime, and potash and magnesia. The 

 silica-potash ratio is relatively steady. When silica equals i, potash 

 varies between 1.16 and 2.18 in the tops and between 1.33 and 2.32 in 

 the roots, except when the substance added to the soil is high in calcium, 

 when the value of potash becomes less than unity in both tops and roots. 



The soda-potash ratio is much more variable, being always more than 

 I in both tops and roots. When mixtures of salts are added to the 

 soil, potash rises to very high relative values. 



There is a suggestion that sodium may perform some functions also 

 performed by potassium, indicating the possibility that sodium might 

 in part replace potassium in fertilizers. 



The calcium-magnesium ratio in spinach, both in leaves and in roots, 

 is exceptional in having a value greater than unity. The only exception 

 is seen in the tops of plants receiving a heavy treatment with calcium 

 carbonate. This fact seems to suggest the practical importance of 

 magnesium salts as fertilizers for spinach. 



