440 MANURING OF POTATOES. 


manuring the potato crop, but incidentally some valuable in- 
formation has been obtained on some other points of great prac- 
ticalimportance. One is the extent to which the effect of 
any manures applied to the crop is controlled by the inherent 
productive capacity of the particular variety of potato grown. 
This was very well illustrated in the Cheshire experiments 
of 1899, where manures were applied to the two varieties 
British Queen and Hough Giant. The application of farm- 
yard manure at the rate of 15 tons per acre produced an 
increase in the yield of the British Queen of 9 tons 18} cwt. 
potatoes, while in the Hough Giant the same manure gave 
an increase of only 7 tons Iocwt. On two other plots a small 
dressing only was applied of a compiete artificial manure, 
which produced an increase of yield in the British Queen of 
7 tons 1 cwt. per acre,-but only 3 tons 14 cwt. in the Hough 
Giant potato. Both results indicated a capacity in the 
British Queen potato to respond to the application of manures 
in a degree quite impossible to the Hough Giant. 
In the Durham experiments of 1898 on plots without manure, 
the Up-to-Date potato gave a yield of 1 ton 17 cwt. tubers 
more than the Bruce potato. But whena dressing of 9} cwt. 
artificial manure was applied, the produce of the Up-to-Date 
potato was increased by 4 tons 14 cwt. while that of the 
Bruce was only increased by 3 tons 6 cwt.. 
In the Glasgow experiments of 1899 a similar contrast was 
found between the Up-to-Date and the Maincrop potatoes, 
both being varieties extensively cultivated in Scotland at the 
present time. On the average of seventeen farms the Main- 
crop potato gave a yield without manure of 4 tons 24 cwt. per 
acre, while the Up-to-Date gave 4 tons 13 cwt. The latter 
potato proved, therefore, the more productive by the moderate 
amount of rof cwt. But when manures were applied the 
results shown below were obtained. 
On each of the three plots treated with different 
kinds and quantities of manures it was found that the manures 
capable of producing an increase of over 5 tons per acre 
in the yield of the Up-to-Date potato were unable to produce 
more than ahout 3 tons increase in the Maincrop. The 
uniformity of the differences on the several plots, each ot 
