Common Scaij of Potatoes. 



51 



Later, Professor Seton conceived the idea of increasing the 

 jnoistiire holding capacity of the soil hy green-inaniii ing, and the 

 present series of experiments is the natural outcome of this sug- 

 gestion. Subsequent experiments have shown that the hy])o- 

 thesis put forAvard could not be maintained, but the treatment 

 •to which it gave rise, has, for some other reason whiV h will be 

 -discussed later, given excellent results. 



The first experiment in which it was put to the test was 

 carried out in 191 1 as follows : — 



Two plots, No. 1 and 2, were selected on '^oil known 

 to produce Scab. On Plot 1 a quantity of fresh grass lawn 

 •mowings was spread at the rate of BO tons to the acre, and when 

 this had withered somewhat, it was forked in. Xo dung was 

 used but a mixture of artificials was applied to each plot. 

 * Two-thirds of each plot was then planted with clean " sets 

 and the remaining third with badly scabbed *' sets " of Dal- 

 housie " potatoes. The plots were then cultivated in the usual 

 •way. 



When harvesting, a great contrast was shown between the 

 respective crops. That from Plot 1, both from the clean and 

 scabbed " sets " Vvas almost entirely free from Scab and the 

 skin of the tubers showed the smooth glossy appearance rarely 

 •seen except on Potatoes raised on peaty soil. 



That from Plot '2 was badly scabbed as usual, the tubers from 

 the scabbed " sets being slightly worse in this respect than 

 those from the clean. 



The respective yields from the two plots and from tlie difterent 

 parts of the same plot were as follows : — 



In addition therefore to the main object of the ('\]>erii:j iit. 

 it is clear that grass provides an excellent uianure for the potato 

 crop and materially increases the yield. It should i\Uo be noted 

 tluit the yield given by the scabbed seed fell considerably ^ower 

 than that froui the clean seed on both plots and on these ;^^i«.uiids. 

 ihe use of cK^aJi seed is to be advocated.''' Scab on the see*l does 

 not, however, appear to have much effect on the amount oi Scab 



* The scabbed seed was from the same sample as that shown in Figure 1 

 but was not obtained from tliesame soiuv<' as tlu' clean seed. It is aj.parently 

 only wliere the scab has attackeil the eyes of the tubers, that the yit Id is 

 affected so adversely i>y it. 



From Clean •• sets." 



From Sral.hfd •• sctb." 

 Per acre, 

 tons cwi. 

 10 15 

 8 



Plot 1, Green Manured 

 Plot 2, untreated ... 



Per acre, 

 tons ewt. 

 18 5 



12 10 



D 2 



