INORGANIC ELEMENTS 0/ MANURES AND CROPS. 



369 



glance over these with reference to their mineral or inorganic con- 

 stituents, as we have already done in so far as the organic matters 

 are concerned ; let us compare, in a word, the quantity and the na- 

 ture of the mineral substances removed in the course of five succes- 

 sive years, in contrast with the quantity and the nature of the same 

 substances supplied at the commencement of the series, and we shall 

 find that the sums of the phosphoric acid, sulphuric acid, and chlo- 

 rine, and of the alkaline and earthy bases of the crops, are always 

 smaller than the quantities of the same substances which exist in 

 and are supplied to the arable soil. 



I shall institute the comparison with the rotation No. 1, which 

 begins with potatoes ; and further, with a continuous crop which, 

 as the one that is most common and convenient, shall be Jerusalem 

 artichokes. I have not thought it advisable to discuss the rotation 

 No. 2, in which beet replaces the potato, because the ashes of these 

 two crops are so much alike, that it may be assumed to be matter 

 of indifference which of the two enters as the drill-crop element into 

 the series. With reference to the Jerusalem artichoke, I shall only 

 remind the reader that the piece of land where it grows receives a 

 dose of manure every two years, in the proportion of 41245 lbs. per 

 acre, which manure contains 2776 lbs. of mineral constituent. Fur- 

 ther, in the course of each winter peat-ashes, in the ratio of 2700 lbs. 

 per acre, are laid on the land ; and that the stems are generally in- 

 cinerated on the spot, and the ashes they contain returned directly 

 to the soil. 



TABLE OF THE MINERAL MATTERS OF THE CROPS AND MANURES IN 

 THE COURSE OF A ROTATION. 



