Manuring of Potatoes. 



171 



a perfectly adequate and effective substitute tor 10 tons 

 of farmyard manure, and that greater profits can be got by 

 growing potatoes with such artificials combined with a 

 moderate quantity of dung than by applying large quantities 

 of farmyard manure alone. 



It is interesting to note that the trials conducted north of 

 the Tweed also confirmed the observations made in the course 

 of the Yorkshire experiments that an increase in the quantity 

 of manures applied did not afford a corresponding return in 

 the crop. Thus a moderate dressing of 10 tons of farmyard 

 manure per acre produced a large increase of crop over that 

 obtained without manure, but additional applications ot 

 manure, either dung or artificials, did not secure a pro- 

 portionately profitable augmentation of the crop. Similar 

 results were recorded in the Lancashire experiments. 



In order to ascertain the composition of the artificial 

 manures best suited for potatoes in combination with dung, 

 plots were arranged at each of the experimental centres 

 referred to above for the determination of the effects of 

 omitting nitrogen, phosphoric acid, and potash respectively 

 from a compound manure applied to the potato crop. At 

 Garforth there was a comparatively slight reduction in the 

 yield when either of the first two was withheld, and a very 

 marked diminution when potash was lacking. It was 

 concluded, therefore, that of the three fertilising substances 

 potash exercised the greatest influence on the potato crop, 

 and that phosphoric acid was not so effective as nitrogen. 

 This conclusion was confirmed by the observations made on 

 the plots where large quantities of these three fertilising 

 agents were in turn used with ordinary dressings of the other 

 two. A further demonstration of the same point was 

 afforded by the results at Cockle Park and in Scotland. At 

 Cockle Park it was found that it was not profitable to add 

 sulphate of ammonia and superphosphate alone to dung, but 

 that the further addition of sulphate of potash* enabled the 

 whole artificial dressing to give an average increase over 



* From a comparison of the results obtained at Cockle Tark with the different 

 potash manures, it appears that sulphate of potash did better than kainit, and 

 muriate of potash was much more effective than the sulphate. 



