158 THE POTATO. 



When the plants are from 10 to 12 inclies high, and the weather is 

 dry, the furrows are lightly earthed up. In dry soils the earthing 

 plough must not be carried very deeply ; and I may say that in the 

 elevated table lands of America, where the natural drought of the 

 climate is often to be apprehended, I have seen very fine crops of 

 potatoes which had never been earthed up at all. The potato, like 

 all plants that are hoed, requires considerable care ; but this care, 

 as it is immediately profitable, is still more so remotely upon the 

 white crops which are to follow. M. Crud reckons at 58.3 the 

 number of days work that are required upon an acre of land which 

 has received between 19 and 20 tons of manure. This is very 

 nearly what we have found to be the truth at liechelbronn, where for 

 the same extent of surface, manured in the same way, we reckon 

 fifty days labor of a man, and rather better than eleven days of a 

 horse. 



In Europe the potato harvest takes place at the end of autumn. 

 In the intertropical Cordillera, where the cultivation depends prin- 

 cipally upon the heat of a very steady climate, the potato remains 

 in the ground from four to seven months, as it is cultivated at a 

 greater or less height above the level of the sea ; it succeeds bp.»» 

 where tfie mean temperature ranges between 13" and 18" centigrade. 

 (56" and 65" Fahr.) In Venezuela, indeed, it is etill cuhivaied in 

 places where the temperature is not far from 2i" centigrade, (76.5° 

 Fahr.;) but I am doubtful that the culture is then advantageous. In 

 warm and moist regions the potato yields a large (juantity of top, 

 and few tul)ers. I have gathered some very bad ones at Riosucio 

 de P]ngurama, a village situate at the distance of about 5900 feet 

 above the level of the sea, where the mean and constant tempera- 

 ture is about 22" centigrade, (72" Fahr.) 



The produce per acre, noted by ditl'erent observers, is as follows : 



There is an obvii>us relation between the quantity of seed-potato 

 planted and the amount of the crop. In Alsace from 25 to 30 

 bushels per acre are usually planted. In some places too much soed 



• This is ilio jiroduri* (»r two harv.-sts, whirti they gntlirr In t)ie snmo year. 



