ON THE ESSENTIAL CONSTITUENTS OF MANURES. 33 



In Plot 4? bone-dust dissolved in one-third its weight of sulphuric acid, 

 consequentlya manurewhich contained both soluble and insoluble phosphates, 

 was employed. 



The economical manure, a manure highly recommended for the growth of 

 root-crops, and used upon Plot 5, contained in 100 parts 



Water 36'525 



Protosulphate of iron 23*756 



Sulphate of lime '860 



Sulphate of magnesia *204 



Bisulphate of potash 4*677 



Bisulphate of soda 10*928 



Sulphate of soda 15-143 



Sulphate of ammonia. 2*648 



Insoluble siliceous matter (sand) .... 5*850 



100*591 



This manure thus contained no phosphoric acid whatever. 



In Plot 6 nut-cake was used. This refuse manure contained 4*863 per 

 cent, of nitrogen and 4*12 of phosphate of lime. 



The dissolved coprolites used in Plot 7 were free from nitrogenized 

 matter. 



In the commercial night-soil manure was found 4*399 per cent, of phos- 

 phoric acid. 



The whole produce of each experimental plot was weighed, and the 

 weight of the trimmed roots calculated per acre. 



The following Table exhibits the yield of the trimmed roots of each plot, 

 calculated per acre, and the increase per acre over unmanured plot : 



Per acre. Increase per acre, 

 tons. cwt. Ibs. tons. cwt. Ibs. 



Plot 1 (guano) yielded 111256 6 856 



Plot 2 (guano and dissolved coprolites) yielded. . 12 16 16 7 12 16 



Plot 3 (bone-dust) yielded 8 16 3 12 



Plot 4 ?bone.superphosphate) yielded 13 12 16 8 8 16 



Plot 5 (economical manure) yielded 6 016 16 16 



Plot 6 (nut-cake) yielded 10 416 



Plot 7 (dissolved coprolites) yielded 1112 6 8 



Plot 8 (unmanured) yielded 5 4 



Plot 9 (commercial night-soil) yielded 940 400 



Plot 10 (mixture of soot, guano, dissolved copro- 

 lites and bone-superphosphates) yielded. .1008 4 16 8 



It will appear from these experiments 



1. That phosphatic manures greatly increased the yield of the root-crop. 



2. That a purely mineral phosphate, when dissolved in acid and quite free 

 from ammonia, gave as large a return as good Peruvian guano, which is rich 

 in ammonia. 



3. That the economical manure, which contained no phosphates, practi- 

 cally speaking, gave no increase in the crop. 



4. That manures which are comparatively poor in phosphates produced 

 less effect than manures rich in phosphates. 



5. That the form in which the phosphates were employed very much affected 

 the result. 



Thus bone-dust treated with sulphuric acid, and consequently containing 

 1859, D 



