On the Exhaustion of Soils, 



By comparing these numbers with those already given (p. 86), 

 as expressing the weights of the several crops, it is easy to calculate 

 the relative value of each crop as expressed by the effect produced 

 in deteriorating the soil. Hence we at once get a reply to the question, 

 whether the largest crop exhausts the soil more, or less, than the 

 smaller ones, in proportion to the amount of food or vegetable 

 matter formed. This is shewn in the following Table which 

 contains the weight of the crop per acre, the quantity of inor- 

 ganic matter removed from the soil by each crop, the quantity 

 of dry organic matter equivalent to 100 parts of the inorganic 

 matter thus abstracted, and the assumed effect produced by each 

 crop, arranged in the order of their exhausting effects. 





Weight of 









12. Superphosphate of Lime 

 15. Phosphate of Soda 



3. Sulphate of Potash 

 10. Sulphate of Magnesia 



627 



594 

 745 



713 

 805 



1366 

 1298 



9. Nitrate of Soda * . 

 16. Rotten dung . 

 2. Phosphate of Ammonia 



457 

 939 



471 



682 

 745 



855 

 892 



1223 

 1222 



1190 



6[ Co t mm e on f salt taSh ' . 

 13. Carbonate of Soda . 

 8. Muriate of Potash 



7 l? 

 653 



702 



1031 





It is evident then from this Table, that the rate of exhaustion is 

 quite independent of the weight of the crop. Thus for example, 

 taking Phosphate of Ammonia as a standard of comparison, it 

 appears that Sulphate of Ammonia produced a smaller, and Muriate 

 of Lime a larger crop ; yet, both of these crops exhausted the soil 

 more than the standard, just in the proportion that 1256 and 1223 

 are more than 1190. Again no manure produced a smaller, and 

 common salt a larger crop, than Phosphate of Ammonia did, but 

 both of them, in proportion exhausted the soil less than the 

 standard in the ratio of 1171 and 1124 to 1190. In arriving at this 



