18 Artificial Manures for Swedes. 



highest state of fertility. For the productive powers of soils, 

 let it be remembered, cannot be increased to an unlimited extent ; 

 when, therefore, a soil is naturally as productive as it can be 

 under any circumstances, or when by good cultivation it has 

 reached its maximum state of fertility, the addition of the most 

 valuable manure, it is evident, cannot produce any perceptible 

 effect. Under these conditions the best fertilizer would produce 

 no greater effect than an utterly worthless and inexpensive 

 manure Now the closer a soil approaches this condition the 

 less it is adapted for the performance of experiments with manures, 

 and vice versa ; land not very productive, or naturally poor, is just 

 in a condition in which the full effects of different fertilizers can 

 be best discerned, and t am inclined therefore to consider the 

 fact of the experiments having been tried on a naturally poor soil 

 as peculiarly fortunate. 



A reference to the tabulated statement which has just been 

 given will exhibit very considerable differences in the weight of 

 the bulbs raised by an equal money- value of different manures. 

 Thus whilst 21. worth of home-made superphosphate of lime 

 gave an increase of 8 tons 8 cwts. 16 Ibs. per acre, 21. worth of 

 economical manure produced merely 16 cwts. 16 Ibs. more per 

 acre than the unmanured portion of the field. Again, it will be 

 observed, that whilst 27. worth of dried night-soil gave only 

 9 tons 4 cwts. of roots, a mixture of guano and dissolved coprolites 

 gave 12 tons 16 cwts. 16 Ibs., and dissolved coprolites alone 

 11 tons 12 cwts. 



These differences are still more strikingly exhibited in the 

 following table, in which the different plots are arranged accord- 

 ing to the increase which the various fertilizers employed upon 

 each produced : the table likewise shows the cost at which 1 ton 

 of increase was produced in each experimental trial. 



Table showing Increase per Acre, and Cost of 1 Ton of Increase, in 

 10 experimental trials upon Swedes. 



Cost of 1 ton of 



Increase per acre. increase, 



tons. cwts. Ibs. s. d. 



No. 1. Home-made superphosphate . . 8 8 16 049 



2. Dissolved coprolites and guano .7 12 16 5 3J 



3. Guano 6 8 56 6 2* 



4. Dissolved coprolites 6 8 063 



5. Mixture of guano, soot, dissolved 



coprolites, and bone super- 

 phosphate 4 16 8 083$ 



6. Nut-refuse 4 16 084 



7. Commercial night-soil 4 0100 



8. Bone-dust 3 12 11 U 



9. Economical manure 16 16 2 9 6f 



10. Nothing. 



(Natural produce 5 tons 4 cwts.) 



