CHAPTER IV 



ROTATION OF CROPS IN VEGETABLE- 

 GARDENING 



WHEN a certain crop has been grown for a number of 

 years in the same field, the yield often decreases with 

 each successive harvest, until, finally, the crop fails to be 

 remunerative. When a different vegetable is planted on 

 such land it usually yields a paying crop, and after a 

 number of years the original crop can again be grown with 

 profit. This phenomenon has given rise to the belief by 

 some persons that the first crop puts something in the soil 

 that is detrimental to itself; others hold that there is 

 something taken out of the soil that is afterward restored. 

 The latter view may be nearer the truth than the former. 

 There are crops, however, that grow "tired" of a certain 

 piece of land, or rather the land grows "tired" of a certain 

 crop. Some of these instances cannot be explained by 

 the exhaustion of certain elements. Certain pieces of 

 land in Germany grew tired of growing beets, and were 

 "riiben-mude" (beet-tired); after growing certain other 

 crops on this land, it would again produce beets in the 

 same quantity as at first. Later investigations showed 

 that this "beet- tired" condition was due to the presence 

 of a microscopic worm closely related to the one that 

 causes root-knot on our vegetables. 

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