MO R r us G R A M 1 N E U S WOE U K N i: M 5 1 S , 263 



Experience has long since proved, that carrots exhaust 

 ?.he soil in a much greater degree than white turnips ; thoughj 

 by this mode of judging, they impoverish land in a less 

 degree than any of these plants. But when we take the 

 weight of nutritive matter which a plant affords from a 

 given space of ground, the results are very different, and 

 will be found to agree with daily experience in the garden 

 and on the farm. 



Potatoes 63^ 



Cabbages 42 



Manoel-wurzel 28 



The i)roportion in wliich they 

 stand to each other, with 



Carrots 24 / respect to the weight of iiii 



Kohl-rabi 17 



Swedish Turnip 16 



Common Turnip 14 



J 



tritive matter per acre, and 

 in exiiaustingr tlie land. 



The effects of some plants are only to impoverish the soil 

 for an immediate succession of the same plant; while others 

 have the property of exhausting the land, not only for an 

 immediate succession of themselves, but likewise for every 

 other kind of vegetable. 



A consideration of the difference in the composition of 

 component parts of the nutritive matter of different species 

 of plants, it appears, will account in some measure for this 

 property. 



It has been already mentioned that the nutritive or solu- 

 ble matter of vegetables consists, for the most part, of five 

 distinct vegetable substances -^ mucilage or starch, saccha- 

 rine matter, gluten or albumen, and bitter extractive, or 

 saline matters. A plant, therefore, whose nutritive matter 

 consists of one or two of these principles only, will impove- 

 rish the soil in a greater decree for an immediate succesion 

 of the same plant, than a different species of vegetable that 

 has its nutritive matter composed of a greater variety of 

 these substances. Hence, plants that have the greatest 

 dissimilarity in the immber and j^roportion of vegetable 

 principles, which constitute their nutritive matter, will be 

 found best fitted to succeed each other in alternate cropping. 

 The dili'erent varieties of wheat consist almost entirely of 



