1923] Soil Treatments of Toxic Material 47 



and hence represent the relative iron accumulations. Summarizing 

 the data in this table, as we did in Table I, we get results which are 

 here compared with the average of Table II. 



Table IV. Average Depression of Iron Accumulation in Nodal Tissues of 

 Corn Compared With Increases in Yield 



Average depression of Average increase 



iron accumulation in yield 



Kainit 9 — 33 



Nitrate of soda 4 — 18 



Acid phosphate 4 - — (accumulation) 13 — loss 



From this, we see that the increase in yield is roughly in propor- 

 tion to the depression of iron accumulation and we assume that the 

 toxic material present in the soil is soluble iron. 



What is the action of the fertilizer materials in preventing ex- 

 cessive accumulation of iron and how do they function in increasing 

 crop yields? Hofifer^ states that root rot is related to metal poisoning 

 and that the greater the accumulation of iron within the tissues the 

 greater the damage from root rot. Any treatment therefore which 

 keeps the iron out may be expected to decrease root rot and increase 

 the yield of corn. The observed facts are that the discoloration due 

 to iron is less and the yield greater when kainit and nitrate of soda 

 are used, and that the discoloration is greater and the yield less when 

 acid phosphate is used. True- has shown that the lupine, which is in 

 the same group as corn, with regard to its acidity-growth relationships 



+ . 

 has considerable difficulty in the seedling stage in absorbing the K ion 



unless certain combinations of ions or salts are present. He finds 

 that the Ca ion, the NO., ion and presumably the CI ion aid the ab- 

 sorption of potash and that the SO_j ion and the H^,PO_, ion interfere 

 with its absorption. 



We are led, therefore, to conclude as follows regarding the action 

 of the fertilizing materials used : 



1. Kainit aids the crop, presumably on account of the effect of its 

 potash on the entrance of iron into the plant. Potash appears to en- 

 able the plant to withstand otherwise toxic amounts or compounds of 



^ Hoffer, G. N. From corresiioiulence with the Nissen Farms. 



2 True, R'odnev H. The function of calcium in the nutrition of seedliug.s. In Jour. 

 Amer. Soc. of Agronomy, Vol. i:!. No. 3, 91-107, March 1921. 



