12 



MASS. EXPERIMENT STATION BULLETIN 378 



Magnesium Requirements of Plants. (Walter S. Eisenmenger and Karol 

 J. Kucinski.) Various species of plants have been grown on an area known 

 to be deficient in magnesium. On the basis of foliar observation in the 

 field it has been possible to separate the different species into two groups 

 according to their apparent tolerance to magnesium deficiency. This 

 classification is as follows: 



Tolerant 



A^ot Tolerant 



Alfalfa 



Apple 



Asparagus 



Beans 



Beets 



Blueberries 



Carrots 



Gladiolus 



Hollyhocks 



Lettuce 



Millet 



Peas 



Rhubarb 



Rye 



Soybeans 



Strawberries 



Sudan Grass 



Sweet Potatoes 



Swiss Chard 



Buckwheat 



Cabbage 



Cauliflower 



Corn 



Cucumber 



Eggplant 



Grapes 



Mangels 



Muskmelons 



Okra 



Peaches 



Peppers 



Potatoes 



Pumpkins 



Radish 



Rape 



Rutabagas 



Spinach 



Squash 



Sunflower 



Tobacco 



Tomatoes 



Turnip 



Velvet Leaf (Abu- 



tilon avicennoe) 

 \Vatermelon 



Chemical analyses of the various plants have shown that when only 

 magnesium was added to the soil all plants increased in magnesium, while 

 their calcium content was generalh^ decreased. Experience has shown 

 that magnesium is more easily introduced into plant tissue than calcium 

 • when additional amounts are added to soil. When magnesium and cal- 

 cium are added to the soil together, the intake of both elements may be 

 decreased. 



Calcium applications hastened the maturity of certain cucurbits. De- 

 termination of sugar in raspberries showed that magnesium applications 

 tended to increase the sugar content while application of both magnesium 

 and calcium produced raspberries with the highest sugar content. 



The Relative Toxicity of Certain Ions and the Function of the Calcium 

 Ion as an Antagonist as Indicated by Soybean Roots. (Walter S. Eisen- 

 menger and Plese Corbett.) It has been recognized in agricultural prac- 

 tice that elements used to stimulate plant growth or as fungicides and 

 insecticides may leave residues in the soil which tend to act as poisons to 

 the plants if applied in sufficiently large quantities. However, if these 

 same elements are applied in moderate quantities, they may be beneficial. 



Seedlings were grown in single salt solutions of calcium nitrate, copper 

 sulfate, lithium carbonate, manganese sulfate, magnesium sulfate, and 

 zinc sulfate. Since the anions of these salts have been found not to in- 

 fluence growth to any appreciable extent, the cations are the factors to 

 be considered. Each of the cations, €&++, Cu-|--f. Li + , .Mg++, 

 .Mn-f-f- and Zn-|--|-, was found to be toxic in single salt solution; but 

 the calcium ion in the form of Ca(No3)2 when placed with any one of 

 the other single salt solutions overcame the toxicity of tlie medium to 

 soybean seedlings. Over wide ranges of concentrations, the mixed solu- 

 tions were less toxic than any of the single ion solutions. 



