102 RESULTS WITH POTATOES 



When the potato crop is grown upon land which has been 

 in grass for a couple of years, the soil will be fairly supplied 

 with humus, and the farmer need have little fear of obtaining 

 the necessary fine tilth for the potatoes. The crop may then 

 be successfully grown with artificials without the use of farm- 

 yard manure. Success would equally attend the cultivation 

 with artificial manures on any kindly loam, unless the season 

 was one of unusual drought. 



The requirements of a potato crop for plant food are very 

 much less than those of a crop of mangel, but the quantity 

 of manure needed for potatoes is by no means so different as 

 would appear from this consideration, the mangel crop being 

 able to feed itself from the subsoil, while the potato derives 

 nourishment from the surface soil only. If early potatoes are 

 grown, an ample supply of food becomes still more necessary, 

 owing to the short period allowed for growth. 



Potatoes grown on lea land will not require the quantities 

 of manure used at Rothamsted to yield a good produce. 

 In the Glasgow experiments, the application of 2 cwts. 

 sulphate of ammonia, 6 cwts. of superphosphate, and 2 cwts. 

 sulphate of potash, without dung, gave an average crop on 

 twelve farms of 5 tons 12 cwts. of saleable potatoes. If, on 

 the other hand, it is desired to grow potatoes on land which 

 has been repeatedly cropped with corn without farmyard 

 manure, the Rothamsted mixture might be employed, with 

 an increase in the superphosphate, as that used at Rothamsted 

 is of very high quality. The manuring might then be 3^ cwts. 

 sulphate of ammonia, 6 cwts. superphosphate, and 3 cwts. 

 sulphate of potash. 



When farmyard manure is employed the quantity of arti- 

 ficial manure will of course be reduced. For early potatoes 

 it is usual to employ a very heavy dressing of dung, which 

 doubtless does somewhat to raise the temperature of the soil. 

 As very early maturity is in this case desired rather than the 

 production of a large crop, it may be questioned whether 

 ammonia salts are not better omitted, and superphosphate 

 and potash salts be made the only addition to the dung. 

 Experience must decide whether a small quantity of sulphate 



