Artificial Manures for Swedes. 19 



We thus see that well-made superphosphate was by far the 

 most economical manure in these experimental trials, and the 

 " economical manure " the worst of all ; for whilst 1 ton of increase 

 raised with the agency of superphosphate of lime was obtained 

 with an expenditure of 4s. 9rf., 1 ton of increase raised with 

 " economical manure " would cost no less than 2L 9s. 6f d. for 

 the manure. 



It is worthy of observation that the land in the preceding year 

 was not manured with farm-yard manure, nor indeed with any 

 manure whatever, and we thus see that with superphosphate 

 alone a better crop of swedes may be raised than with guano. 

 It will be seen that guano produced nearly 2 tons less of swedes 

 per acre than home-made superphosphate, a difference which, 

 considering the small crop furnished by the unmanured land, is 

 considerable, Peruvian guano alone, indeed, should not, as is 

 so often the case, be employed for root-crops, for when employed 

 in small quantities the per-centage of phosphates contained in it 

 is not adequate to enlarge the roots sufficiently, and when used 

 in large quantities it is apt to produce an excess of leaves, which 

 is generally the case with all manures containing like guano a 

 large amount of nitrogenized constituents. Had the experiments 

 been tried on wheat instead of swedes, there can be little doubt 

 but that the results would have been different, and guano, in all 

 probability, would have carried off the palm, for it is on the 

 cereals and upon grass-land that highly nitrogenized manures 

 like guano, soot, blood, &c., produce the most beneficial effects. 

 Next to superphosphate made from bones, the mixture of dis- 

 solved coprolites and guano gave the greatest increase, the crop 

 weighing 12 tons 16 cwts. 16 Ibs. per acre; whilst dissolved 

 coprolites employed alone furnished 1 1 tons 1 2 cwts. per acre. 

 This is an exceedingly interesting result, for it shows that a 

 purely mineral phosphatic manure, even when applied in a form 

 in which it can readily be assimilated by plants, does not pro- 

 duce, at least on a poor soil, so large a crop as a mixture in 

 which a portion of the mineral phosphate is replaced by a manure, 

 which, like guano, is rich in nitrogenized constituents. A small 

 amount of an ammoniacal manure, or a fertilizer rich in organic 

 matters, readily furnishing ammonia on decomposition, appears 

 to be sufficient to secure the assimilation of the mineral phos- 

 phate ; for it will be observed, by glancing at the experiment in 

 which a mixture of soot, guano, superphosphate, and dissolved 

 coprolites was used, that if the amount of organic fertilizing 

 matters in a mixture is increased at the expense of its phosphatic 

 constituents, the produce will be reduced. Thus this mixture, in 

 which a portion of superphosphate was replaced by soot and 

 guano, both containing much ammonia, or furnishing it on decom- 



