204 AGRICULTURE 



for turnips, if oats or wheat partly take 

 the place of barley, and if oats replace a 

 certain proportion of wheat. The displace- 

 ment of one-half of the turnip break by 

 potatoes or mangolds is found to be desirable 

 on land that is much addicted to finger-and- 

 toe, so that, under this modification, instead 

 of any field coming under turnips or swedes 

 once in four years, a cruciferous crop would 

 recur only at intervals of eight years. If 

 care be taken not to reinfect the land by the 

 application of farmyard manure contamin- 

 ated with the germs of finger-and-toe, the 

 Norfolk four-course rotation, modified as 

 indicated, can be depended upon on most 

 soils to secure sound crops of turnips or 

 swedes. Then, again, if it is found that any 

 particular farm or field shows clover sickness 

 in a pronounced form, it may be necessary, 

 instead of having one-fourth of the tillage 

 area under clover, to be satisfied with only 

 one-eighth ; the area of clover so displaced 

 being cultivated with beans, peas, or vetches, 

 crops, namely, of the same natural order as 

 clover, and therefore capable of enriching 

 the land with nitrogen derived from the 

 atmosphere through the action of the minute 

 organisms associated with their roots. So 

 far as combating clover sickness is concerned, 



