SOS AGRICULTURAL TEXT-BOOK. 



When we come to compare the balance left in the soil .after these two rotations, sup 

 posing the bean crop to have succeeded in both, we find that with the green rye and 

 turnips there is a large deficiency both of nitrogen and potash, that of the latter 

 amounting to 84 Ibs. per acre, or in other words the soil would have had to supply 

 84 Ibs. of potash, in addition to that supplied by the manure in order to grow a crop 

 cf beans, whereas in the rotation where the rye was allowed to stand for seed, there 

 was a large excess of potash, and a sufficiency of nitrogen.&quot; 



The above also elucidates a principle which the practical farmer should never lose 

 sight of; viz, that a field may prove barren for a given crop, such as wheat, from the 

 deficiency of only one or two constituents ; andjthat, in order to supply this deficiency, 

 our cheapest course generally is to give to the soil that peculiar material. Suppose I 

 have a field which refused to grow wheat, in consequence of impoverishment. Am 

 I to supply barn-yard manure, which contains every thing the wheat crop can require, 

 but which is costly owing to the quantity which I must haul from a distance and 

 pread? or shall I apply 3 cwt of guano, and 100 pounds of super-phosphate of lime, 

 on the supposition that nitrogen and phosphoric acid alone are wanting? In the 

 Michigan Oak openings we have reason to believe that it is a deficiency of these two 

 materials only which renders the soil less fertile than it used to be ; but a chemical 

 analysis can alone positively decide the matter. In practice the question would be 

 one of cost, supposing the barn-yard manure to be good : but the amount of common 

 dung requisice to supply the nitrogen, phosphates and potash of the above named 

 guano and bones, would have to be very much larger than we are in the habit of using 

 to the acre. The above also teaches, that while a field may refuse to grow one crop 

 profitably, it may be quite capable of growing another and different class of plants. 



677. Before manures can produce their full and profitable 

 effect upon the soil, the land must be laid dry by drainage or 

 other means. It must also be cleaned and kept clean from 

 weeds. 



678. The value of the various constituents of manure may 

 be thus classified ; and the money cost, in the Western States r 

 of any given manure can easily be estimated by the quantity of 

 the following ingredients which it contains, in a soluble form. 



1. Nitrogen. 



2. Ammonia. 



3. Phosphoric Acid. 



4. Sulphuric Acid. 



5. Soda. 



6. Chlorine. 



7. Potash. 



8. Magnesia. 



9. Iron and Manganese. 



10. Lime. 



11. Carbon. 



12. Soluble Silica. 



679. It is impossible to ascertain by theory alone and with 

 out actual experiment, the exact effect which a given manure 

 will produce upon a given soil or crop. The mechanical con- 

 it shows that there were 92 Ibs. less nitrogen and 84 Ibs. less potash than the bean 

 Crop required, and it appears to be taken for granted that the soil contained none of 

 these constituents except where they had been artificially supplied.) 



