192 AGRICULTURE 



of sainfoin, for although this perennial plant 

 will grow for several years in succession on 

 the same land, it is found that poor results 

 are got by breaking up the sainfoin ley, 

 and immediately, or even after a short 

 interval of years, seeding down again with 

 sainfoin. 



The impossibility of growing certain crops, 

 and the difficulty of growing others in suc- 

 cessive years, or at too close intervals, is 

 probably to be traced to more causes than 

 one. But the cause that most frequently 

 interposes a barrier is the presence of disease, 

 the germs of which may linger in the land 

 from one crop to the next, but which can be 

 starved out if the particular host on which 

 they prey is not brought within their reach 

 while they still retain their vitality. Where 

 there is a difficulty in growing the same crop 

 in successive years upon the same land it is 

 frequently said that the land is " sick " to 

 that particular crop. One often hears it 

 said that land is " clover sick " the idea it 

 is intended to convey being that this crop 

 cannot be grown on some particular area 

 until the land has had a rest from the growth 

 of this crop. What the particular disease is 

 that prevents the continuous or frequent 

 growth of this crop has not been fully worked 



