r^^s 



r^ 



288 



The effects of some plants are only to impoverish the soil for an immediate succession of th 

 same plant; while others have the property of exhausting the land, not only for an immediat 

 succession of themselves, but likewise for every other kind of vegetable. 



A consideration of the difference in the composition or component parts of the nutritive mit 

 ter of different species of plants, it appears, will account in some measure for this pronertv 



) 



vege- 



ve- 



tables consists, for the most part, of five distinct vegetable substances — mucilao-e or starch 

 charine matter, gluten or albumen, and bitter extractive or saline matters. A plant therefoi'e 

 whose nutritive matter consists of one or two of these principles only, will impoverish the soil in 

 a greater degree, for an immediate succession of the same plant, than a different species of 

 getable that has its nutritive matter composed of a greater variety of these substances. Hence 

 plants that have the greatest dissimilarity in the number and proportion of vegetable principles 

 which constitute their nutritive matter, will be found best fitted to succeed each other in alter- 

 nate cropping. The different varieties of Wheat consist almost entirely of starch and gluten, 

 while Barley, Pease, and Turnips, contain a greater proportion of saccharine matter which is 

 wanting in Wheat, and are consequently best qualified to precede, or follow that grain, in alter- 

 nation with green crops. Oats, Rye, and Beans, afford nutritive matters similar to Wheat, 

 though in less proportion; and a crop of either of these will have a like effect on the soil as 

 that of Wheat, though in a less degree, but totally different from those of Barley, Pease, and 

 Turnips. The former plants, therefore, as they impoverish the soil only for an immediate sue- 

 cession of themselves, msij he termed partial impoverishers ; and the latter, exhausting the land 

 for themselves, as well as, in a degree, for every other kind of vegetable, may be called genera! 

 impovcrishers, , 



If the nutritive matters of the following plants be examined with this view, they will be 

 found to rank either as general or partial impoverishers. 



General IiDpoverishers. 



Oats, 



Rye, 



Potatoes, 



Carrots, 



Mangel-wurzel, 



Partial Inipoverlsliers. 



Wheat, 

 Pease, 



B 



cans. 



Turnips, 



Cabb 



a 



ges 



Kohl-rabi, 

 Bunias orientalis. 



CI 



overs. 



Sainfoin, 



Lucern, 



Grasses when mown. 



It does not fall within the limits of these pages, to give an account of all the plants employed 

 in \he Alternate Husbandry, but only of such as have been more particularly submitted to expe- 

 riment in this Series. There has been, however, several plants of this class made trial of, with 

 respect to the quantity of nutritive matter they contain, some account of which will be found in 

 the Notes, beginning at page 310. 



