162 Experiments upon Swedes. 



appears to prove satisfactorily that sulphuric acid was not wanted 

 in the experimental field. 



6. As sulphate of ammonia proved inefficacious when used by 

 itself, or in conjunction with soluble phosphates, either the 

 ammonia had no effect upon the swedes and might have been 

 dispensed with, or the quantity of sulphate of ammonia was too 

 large, and had injured the young plant, and to some extent had 

 retarded its progress. I believe both to have been the case. 

 Further experiments will show whether or not nitrogen, applied 

 in other forms than that of ammonia, has a better effect upon 

 roots, and also whether or not the result would have been dif- 

 ferent, if sulphate of ammonia had been more sparingly used. 

 One series of experiments is totally unfit to dispose of so impor- 

 tant a question as that of the utility of nitrogen for turnips. 

 Without entering therefore further into the theoretical aspect of 

 this question, I would observe, that sulphate of ammonia greatly 

 retarded tlie germination of the turnip seed, and, instead of 

 rapidly pushing on the young plant, it kept the plant back, and 

 throughout tlie experimental period the turnips on plot No. IV. 

 were far behind all the others. When devising the experiment 

 with sulphate of ammonia, I expected to see a luxuriant develop- 

 ment of the leaves at the expense of the bulbs, but, to my great 

 astonishment, the leaves of the turnips on No. IV. were much 

 smaller than those of the adjoining plots Nos. Ill, and V., and 

 certainly not larger than the leaves of the unmanured turnips. 

 In No. v., on the other hand, I observed, to some extent, the 

 effects which are generally ascribed to ammoniacal manures. The 

 leaves in No. V. had a much darker appearance than in other 

 plots, not dressed with sulphate of ammonia, and the plants on 

 this plot looked on the whole the most luxuriant. It is thus 

 plain that ammoniacal salts like sulphate of ammonia are only 

 leaf-producing manures, if they find in the soil or manure the 

 proper mineral constituents which are essential to the formation 

 of the leaves. My experience on this subject is not mature 

 enough to speak with confidence on the relative value of ammonia 

 for root-crops generally, and its functions in relation to other 

 cultivated crops ; but I can well conceive that on well-cultivated 

 soils, rich in those mineral matters required by root-crops, ammo- 

 niacal manures may be used with advantage even for root-crops ; 

 whilst on poor thin soils, deficient in available phosphates, am- 

 monia will do more harm than good. In the experiments here 

 recorded, sulphate of ammonia used by itself had no effect what- 

 ever on the development of turnip-tops ; used in conjunction 

 Avith soluble phosphate it appeared to favour the growth of leaves. 

 I regret not having weighed the tops, to verify this observation 

 in the field. 



