DIVISION OF BOTANY 487 



SESSIONAL PAPER No. 16 



4. Lime-sulphur. Yield 7 bushels. Scabbiness 45. 



5. Lime-sulphur. Yield 5| bushels. Scabbiness 35. Many tubers quite clean. 

 2. Sawdust. Foliage exceptionally green compared with other plots. Yield 



%\ bushels. The sawdust was apparently in the same condition as when applied, 

 no decomposition being visible. 'A few clean tubers, but most very scabby. 

 Scabbiness 75. 



7. Yield 4 bushels. Tubers small. Vines weak and spindly. Scabbiness SO. 



8. Yield ?>\ bushels, otherwise much like the last. 

 10. Yield 2 bushels. Scabbiness about the same. 



12. Yield 2 bushels. Scabbiness about the same. Stand very uneven. 



9. Yield I bushel. Very few plants properly developed, and long bare 

 spaces present in the rows where plants had not come up. Scabbiness over 80. 



In examining these results, it will be noticed that the sawdust had little effect, 

 the amount of scab being almost as high as on the best check plot. Presumably any 

 beneficial effect it could have would be due to its decomposition, perhaps by its 

 decomposition increasing the acidity of the soil, and therefore could hardly be 

 looked for when so little alteration had taken place. 



While no benefit was obtained from powdered sulphur there was a marked 

 improvement where the soil was sprayed with lime-sulphur solution. The plot 

 which received the double quantity showed rather less scab, but also a considerably 

 diminished yield. As applied, the lime-sulphur was much diluted with water, which 

 would, of course, increase the labour and cost of application, and no test was made 

 with the undiluted substance, but even if the latter were just as effective, an applica- 

 tion at the rate of 200 gallons or more per acre would be too expensive for ordinary 

 purposes. There is also the objection that this result was obtained from a single 

 experiment and might be due to a variation in the degree of infection of the soil or 

 some other factor not accounted for, although, as far as could be judged, the con- 

 ditions were uniform. The experiment at any rate would seem to be worth repeating. 



With respect to chloride of lime, it is evident that even a comparatively small 

 amount (200 lb. per acre) applied twelve days before planting exercised a markedly 

 injurious action on the ci'op, while, on the other hand, when applied in such 

 quantities as to render growth almost impossible, such tubers as are found are almost 

 as badly scabbed as those on the check plots. It is, however, to be noted that little 

 or no rain fell between the time of application of the chloride and that of planting. 

 This would probably affect the results adversely in two ways. In the first place the 

 germicidal constituent would not be so extensively and intimately diffused through 

 the soil and therefore its effect on the scab organisms present would be restricted, 

 and secondly its alteration into substances harmless to the crop would probably be 

 slower. While the labour and cost of applying this substance in sufficient quantity 

 in a state, of suspension in water would seem to be prohibitive under field conditions, 

 it would still seem to be necessary to try the effect of applications similar to those 

 here given, made in the autumn instead of late spring, before concluding that it has 

 no value in reducing scab. 



It will he noticed that disinfection of the seed tubers whether with formalin or 

 corrosive sublimate, produced no improvement in the scabbiness of the crop. This 

 was naturally to be expected when the soil was so badly infected with the disease, but 

 as this fact is, even now, not always recognized, it may not be amiss to call attention 

 to it. 



J. W. EASTHAM. 



