38 



leave practically nothing. It is now thought that 

 the roots of certain kinds of crops exude some ma- 

 terials more or less poisonous to themselves, which 

 in the end seriously interfere with the growth of 

 that particular plant. While nothing definite is 

 known of such self-poisoning in connection with 

 any particular vegetable, yet such a condition is 

 doubtless possible and worth remembering in 

 considering the value of rotation. Another rea- 

 son for rotation is the varying prices secured 

 for various crops. The keen, alert vegetable gar- 

 dener who has made a careful study of market con- 

 ditions should be able to foretell, in many cases, the 

 crops that are likely to be in greatest demand. In 

 this way a shifting of the crop scheme from time 

 to time can often be made extremely profitable. 

 Over small areas wide rotations are not possible, 

 but the various kinds of vegetables may be shifted 

 from place to place each year, thus gaining many 

 of the advantages of rotation. 



The farm garden can be so planned that the entire 

 area devoted to vegetables can be changed each sea- 

 son. This is, perhaps, the ideal arrangement. In 

 connection with commercial gardening the land is 

 too valuable to be left idle or occupied by a farm 

 crop for a given season, but the areas planted to 

 each crop are much larger, and for this reason their 

 shifting will be much more effective, not only in 

 conserving plant food, but in avoiding many serious 

 insect and disease troubles. Whenever possible, 

 from three to five years should elapse between crops 

 of the same class. That is, cucumbers, melons or 

 squashes ; or cabbage, cauliflower, Brussels sprouts, 

 kale, radishes or turnips should ever follow each 

 other, except at the intervals indicated above. 



