20 Artificial Manures for Swedes. 



position, only gave 10 tons 8 Ibs., whilst the produce of the dis- 

 solved coprolites amounted to 1 1 tons 12 cwts. 



Dissolved coprolites, which follow guano in the above list, 

 virtually produced as great a crop as guano, for the difference of 

 56 Ibs. is not worthy of consideration. Whenever coprolites 

 therefore can be had at a cheap rate, they may be employed as a 

 substitute for bone-dust, provided care is taken to dissolve them 

 properly in sulphuric acid and to mix them with some nitro- 

 gen! zed organic manure. 



The nut-refuse gave as nearly as possible the same produce 

 as the mixture in experimental plot No. X., and commercial 

 night-soil follows next in the list. A comparison of the crop 

 yielded by bone-dust with that yielded by bone-dust dis- 

 solved in sulphuric acid, will forcibly exhibit the advantages of 

 applying bones in the latter form ; for whilst an equal money 

 value of bone-dust only gave an increase of 3 tons 12 cwts., dis- 

 solved bone-dust gave an increase of 8 tons 8 cwts. 16 Ibs. ; or 

 whilst 1 ton of increase raised with the agency of superphos- 

 phate only cost 4s. 9rf., 1 ton of increase raised with bone-dust 

 implied an expenditure of 11.'. \d. The form in which an 

 artificial manure is applied to the land thus greatly influences 

 its action. 



On the whole, we may learn from these experiments that the 

 value of different artificial manures for a crop of swedes, and no 

 doubt also for other root-crops, principally depends on the 

 amount of phosphoric acid contained in them in a form in which 

 it can be readily assimilated by the plants. In bone-dust there 

 is much phosphoric acid ; but when it is used in an unprepared 

 state, in which it still contains all the fat naturally present in 

 fresh bones, it often remains in the soil for a very long time 

 without readily undergoing decomposition, or that preparation so 

 necessary to bring out its full fertilizing effect. All the experi- 

 ments confirm the general conclusion which has just been 

 expressed ; but more especially the experiment with the economic 

 manure, in which the absence of phosphoric acid was proved by 

 analysis, shows the necessity of applying to root-crops a fertilizer 

 containing a good deal of phosphoric acid. Whatever else the 

 virtues of the economical manure may be, it certainly proved the 

 least economical dressing of all, as it produced only 6 tons 16 Ibs. 

 of swedes per acre, or only 16 cwts 16 Ibs. more than the 

 unmanured portion of the experimental field. 



In conclusion I will observe that I have carefully determined 

 the chemical composition of the roots of each experimental plot, 

 in so far at least as it appeared desirable in order to form some 

 idea as to the nutritive value of the swedes raised with different 

 manuring matters. 



