34 REPORT 1859. 



soluble phosphates, yielded an increase of 8 tons. 8 cwt. 16 Ibs. over un- 

 manured plot, whereas an equal money value of bone-dust undissolved yielded 

 an increase of only 3 tons 12 cwt. 



6. That guano proved to be a less economical manure for Swedes than 

 superphosphate. 



Experiments upon Swedes made in 1856. 



The preceding experiments sufficiently show the great importance of 

 phosphates presented in a soluble condition to the crop of Swedes. They 

 appear likewise to indicate that nitrogenized or ammoniacal manures are not 

 so essential as phosphates for the production of a good crop of roots ; but 

 they do not touch the question whether or not ammonia can be entirely dis- 

 pensed with in the cultivation of turnips. This is an important question, for 

 of all fertilizing matters ammonia is the most expensive. 



My attention therefore was chiefly directed in the next series of experi- 

 ments to study the influence which purely ammoniacal manures exert on the 

 growth of Swedish turnips. 



Reviewing the experiments made in 1855, it may appear that the nitroge- 

 nized matters and ammonia contained in the manures employed had some 

 share in the production of the increase ; for it will be remembered that the 

 addition of a small quantity of guano to dissolved coprolites had a very be- 

 neficial effect. Again, the fact that bone-superphosphate, containing from 

 2 to 2^ per cent, of ammonia, gave a much larger return than the mineral 

 superphosphate, might seem to indicate that ammonia in moderate propor- 

 tion is a desirable fertilizing ingredient of a turnip manure. 



A critical examination of these facts, however, I think neither proves nor 

 discountenances the conclusion that ammonia has had a beneficial effect on 

 the recorded experiments ; for when comparing the effects of bone-superphos- 

 phate with dissolved coprolites, no account was taken of the proportion of 

 soluble phosphate contained in each. I have since ascertained that the dis-. 

 solved coprolites contained most of the phosphate in an insoluble state, not 

 near enough acid having been employed for dissolving the coprolite powder. 

 Indeed the coprolite manure contained but little soluble phosphate ; and as 

 insoluble phosphate, in the shape of coprolite powder, has little or no effect 

 upon vegetation, whilst the insoluble phosphates in bone-dust, partially de- 

 composed by acid, unquestionably are sufficiently available to produce an 

 immediate effect on the turnip crop, the difference in the result may have 

 been due to the larger amount of available phosphates, and not to the am- 

 monia contained in the bone-phosphate. On the other hand, the addition 

 of some guano to dissolved coprolites having produced a beneficial effect, it 

 may be inferred that the ammonia in the guano helped to produce this effect ; 

 but since Peruvian guano contains both soluble phosphates and insoluble 

 phosphate of lime in a highly finely-divided state, it may be maintained with 

 equal force that the additional produce resulted from the additional quantity 

 of available phosphates in guano. In short, the experiments in 1855 are not 

 calculated to decide the question whether or not ammonia can be dispensed 

 with as a manuring constituent in a turnip manure. 



With a view of throwing some light on the action of ammonia on root- 

 crops, I made in 1856 the following field experiments : 



A portion of a field was divided into twelve parts of one-twentieth of an 

 acre each. The seed was sown on the 21st of June. 



The soil on analysis yielded the subjoined results: 



