636 



Journal of Agriculture, Victoria. [ii Sept., 1911. 



various manurial dressings on the yields of the different sections. The 

 irregularity of the attack of Blight was common to every field ; frequently, 

 a patch of a few yards in extent would not have a sound tuber, whilst at 

 no great distance the percentage of sound tubers ranged from 70 per cent, 

 to 80 per cent. 



In order to ascertain the influence of pasture in rotation with general 

 cropping, it would be necessary to establish a field or plot to be worked on 

 these lines for a lengthy period. 



IX. — Manurial Tests at Daylbsford, Dean, and Romsey. 



Percentage of Tubers Affected with Irish Blight. 



An accurate account of the weight of diseased tubers in each variety in 

 the different plots was taken in order to find the comparative resistance to 

 Irish Blight; also to find out whether the manures had any effect in 

 minimizing or increasing the virulence of the disease. From the accom- 

 panying tables it will be seen that some varieties were so badly 

 diseased as not to be worth digging. These are stated as resulting in 100 

 per cent, of disease, because only here and there could a sound tuber be 

 found. As, under such conditions, no grower would attempt to harvest the 

 crop, they may therefore be properly regarded as a failure. 



As far as the influence of the manures on the amount of disease is con- 

 cerned, the results given in the summary of plots show that the section con- 

 taining a nitrogenous manure had the highest percentage of disease (80.2 

 per cent.), closely followed by the unmanured .section with 79 per cent. 

 There can be no doubt that, where a nitrogenous manure causes a luxuriant 

 growth of foliage, the disease does a greater amount of damage. This 

 was shown in a marked manner in section D of the Colac plot, where it 

 reached 69.4 per cent. In the unmanured section at Leongatha only one 

 variety produced tubers ; all the others failed. Sections A and B, dressed 

 with superphosphate, gave the lowest percentage of disease. This has been 

 confirmed by reports from several growers. - 



Varieties. — It is a common thing to meet with certain \'arieties which 

 are spoken of as Blight-proof. This arises, in a large measure, from the 

 fact that where several are planted in the same field some will be badly 

 attacked by the disease and one will escape. A case in point. Green Moun- 

 tain, occurred in the Colac plot. By many, the one that escapes is often 

 called Blight-proof, although in another plot it may be totally destroyed 

 by the disease. 



