Artificial Manures for Swedes. 
105 
highest state of fertility. For the productive powers of soils, 
let it be remembered, cannot be increased to an unlimited extent; 
when, tlicrefore, a soil is naturally as productive as it can be 
under any circumstances, or when by fj^ood 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 I am inclined thei'efore 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 lbs. per acre, 21. worth of 
economical manure produced merely 16 cwts. 16 lbs. more per 
acre than the unmanured portion of the field. Again, it will be 
observed, that whilst 21. 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 lbs., 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 7o« of Increase, in 
10 experimental trials upon Swedes. 
Cost of 1 ton of 
Increase per acre. increase, 
tons. cwts. ll)s. £ s. d. 
No. 1. Home-made superphosphate . . 8 8 16 0 4 9 
2. Dissolved coprolites and guano .7 12 16 0 5 3J 
3. Guano . . . , 6 8 56 0 6 2^ 
4. Dissolved coprolites 6 8 0 0 6 3 
5. Mixture of guano, soot, dissolved 
coprolites, and bone super- 
phosphate 4 16 8 08 3^ 
6. Nut-refuse 4 16 0 084 
7. Commercial night-soil 4 0 0 0 10 0 
8. Bone-dust 3 12 0 0 11 U 
9. Economical manure 0 16 16 2 9 6f 
10. Nothing. 
(Natural produce 5 tons 4 cwts.) 
