24 WHEAT RESISTANCE TO TOXIC SALTS. 



average much the most toxic of the salts used. It was the most injuri- 

 ous in every case except in two instances, in one of which sodium 

 carbonate and in the other magnesium clik)rid proved more toxic. 

 It required a sohition of magnesium sulpliate twice as concentrated 

 as that of sodium carbonate to be equally toxic to the Budapest 

 variety, the limits in this case being 0.01 normal magnesium sulphate 

 and 0.005 normal sodium carbonate. The other instance referred to 

 is not so marked. Magnesium chlorid is found to be somewhat more 

 toxic than magnesium sulphate for one variety — Turkey — the limits 

 being for magnesium chlorid 0.0075 normal and for magnesium 

 sulpliate 0.01 iu)rmal. 



Comparing the average toxic limit for each salt, as stated in the 

 tables that follow, magnesium sulphate is one and two-sevenths times 

 !js injurious as magnesium chlorid, one and tliree-sevenths times as 

 injurious as sodium carbonate, three and hve-sevenths times as inju- 

 rious as sodimn bicarbonate, little more than six times as toxic as 

 sodium sulphate, and seven and five-sevenths times as injurious as 

 sodium chlorid. 



Magnesium sulphate in the soil is not considered injurious to am' 

 appreciable extent, but this is no doubt due to the neutralizing effect 

 of other salts with which it is associated. Kearney and Cameron, 

 in their experiments on Lnp/nns alhus nnd Medicago sativa, found 

 magnesium sulphat(> in pure solutions to be the most toxic of all the 

 salts. The writer found the same true for the lupines. But when 

 other salts are added to a solution of magnesium sulphate, toxicity, 

 both absolute and relative, is altered. Kearney and Cameron " say: 



Addition of sodiiuii sulphate, wliifli itself is injurious in pure solution, raises 

 the limit of nia,i,'nesiuni sulphate three times, while the presence of calcium sul- 

 l)liate allows a small ])roi)ortion of the roots to barely survive during twenty- 

 four hours in a solution of magnesium sulphate 480 times as concentrated as 

 that wliifli in ]>nre solnlions represents the limits of endurance. 



To lower classes of plant life magnesium sulphate is apparentW 

 much less toxic. Dr. B. M. Duggar '' has made some experiments 

 with marine'alga' to determine the nutrient value of the salts of some 

 of the alkalis and alkali earths when added to sea water. He found 

 that after the acids and some of the salts of the heavy metals the 

 potassium phosphates proved most toxic. The least toxic were the 

 salts of sodium and magnesium, while the sulphate of magnesium 

 was the least injurious of all the salts used. The less injurious effect 



"Some Mutual Relations I'.ctween Alkali Soils and Vegetation. Ueiuirt No. 

 71, I'. S. l)ei»artm(M!t of Agriculture (1!!02). 



''Tin* Toxic lOffccl of Some Xulrit>n( Salts on Certain .Marine Alga". Science, 

 N. S., IT: i",'.) (i;)03). 



