GENERAL HISTORY OF FIELD GROWING ROOTS 95 



Swedes for four seasons, 1849-1852. Barley was then grown 

 for three years to equalise the soil conditions, and the plots 

 were rearranged on substantially the plan they occupy to-day. 

 Swede turnips were grown for fifteen seasons, 1856-1870, but 

 it was found impossible to continue the growth of Swedes 

 upon the same land year after year with any success. This 

 was mainly due to the incidental circumstance that on growing 

 the same description of crop, with the same comparatively 

 limited and superficial root-range, for so many years in 

 succession, the surface soil became less easily worked, and the 

 tilth, so important for turnips, was frequently unsatisfactory ; 

 whilst for want of variety and depth of root-range of the crop, 

 a somewhat impervious pan was formed below. After the 

 Swedes sugar-beet followed for five years with the same 

 manures, except that in the last two the nitrogenous manures 

 were omitted, and in 1876 mangolds took the place of sugar- 

 beet and have continued ever since. No difficulty has been 

 experienced in growing mangolds continuously on the same 

 land, as may be seen from the fact that the twenty-fifth crop in 

 1900 was the largest of the series. This success must be 

 attributed partly to the extended root-range of the mangold, 

 partly also to its freedom from insect and fungoid attacks, 

 which tend to accumulate on land carrying one crop con- 

 tinuously. The only difficulty is experienced on the plots 

 receiving saline manures only, especially where large dressings 

 of nitrate of soda are repeated every year. Owing to the 

 constant removal of organic matter and the injurious action of 

 the saline manures upon the texture of the soil the land gets 

 into a bad mechanical condition, very sticky when wet, and 

 drying with a hard crust, so much so that there is occasionally 

 a complete loss of plant from this cause alone. 



In the Hoos field experiments upon potatoes were begun 

 in 1876, and continued for twenty-six years ; they were then 

 discontinued, because the crop on the plots receiving no organic 

 manures had fallen to a very low ebb in consequence of the 

 deterioration of the texture of the soil. But on the plots 



