MANURING AND FERTILIZING 33 



4. Increase the quantity of water transpired per gram 

 of dry matter. 



Hecke' shows that the appHcation of potassic fertil- 

 izers has a marked influence in the produdlion of 

 tubers and roots, and that potash assists in the forma- 

 tion of starch. Lawes and Gilbert^ noted that the 

 percentage of potash was relatively high when the 

 supply of it was relatively liberal and vice versa, but 

 the variations are small, and that where there was a 

 deficiency of potash in the supply and in the ash there 

 was generally an increased supply of lime in the ash. 



Which is the Better Source of Potash, Sul- 

 phate or Muriate of Potash ? — This question is 

 still unsettled, because, apart from other considerations, 

 one of the deciding fadlors is the relative cost of each. 

 In many cases the results are inconclusive,' while in 

 some cases* the fertilizers appear to be of equal value. 

 In others' sulphate of potash gave better results; thus 

 Davidson, of Virginia,'' found that the potatoes grown 

 by sulphate of potash contained more dry matter but 

 a less percentage of starch than those fertilized with 

 muriate of potash. Brooks' found that sulphate of 

 potash gave a greater yield per acre of merchantable 

 tubers, which were of larger size and of superior eat- 

 ing quality, containing 2 to 3 per cent, more starch, 

 and, when cooked, the potatoes were whiter, of better 

 flavor, and more mealy. 



1 E. S. R., VII., p. 667. 2 Rothamsted Memoirs, Vol. VI., "Experi- 

 ments on the Growth of Potatoes." ^ (N.Y.) Geneva Bui. 137, pp. 604, 620. 

 * N. H. Bui. 41, p. 13. * Mass. (Hatch) Report, 1896, p. 22 ; R. I. Bui. 65, 

 p. 133 ; Mich. Bui. 131, p. 10; (N. Y.) Geneva, Bui. 137, pp. 621, 622. * Va. Bui, 

 92, pp. 107, 108. ' Mass. (Hatch) Report, 1904, p. 122. 



