32 THE POTATO 



beneficial as it should be; hence, such soils need liming 

 before full benefit can be derived from the use of this 

 fertilizer. A mixture of two-thirds dried blood and 

 one-third nitrate of soda, or of equal parts of all three 

 fertilizers, is suggested. At the Tennessee Experiment 

 Station' cottonseed-meal was found to be a more profit- 

 able source of nitrogen than nitrate of .soda, while at 

 the Florida Station^ the nitrogen of cottonseed-meal 

 and castor pomace were equall)^ effecftive, but that of 

 nitrate of soda was more so by 30 per cent. 



The Influence of Potash.— Wilfarth and Wim- 

 mer ' show that w^hen potassic fertilizers are applied to 

 a soil almost destitute in potash they — 



1 . Increase the size of the tuber, but have little influ- 



ence upon its composition, and that the amount 

 of potash in tubers remains fairly constant, unin- 

 fluenced by the amounts in the soil, or applied, 

 unless very hea\^ applications are made, which 

 may cause an increase to a certain point, but will 

 be attended by a decline if continued. 



2. Decrease the percentage of stems and leaves, but 



have no marked influence on the roots of potatoes. 



3. Have a marked influence on the shape and appear- 



ance of the leaf; if deficient, the leaves are yellow- 

 ish-browm in color, and become spotted or striped 

 in the portions between the veins, while the peti- 

 ole of the leaf and ribs retain their dark green 

 color. If the supply of potash is insufficient the 

 leaves tend to curl, and sometimes collapse of the 

 plant follows. 



1 Tenn. Bui., Vol. XIII., No. 3, p. 6. ' Fla. Report, 1900-1901, p. 27. 



» E. S. R., XIV., p. 561. 



