210 SUGGESTIONS FOR EXPERIMENTS 



differences are small enough to be within the limits of the 

 ordinary errors of analyses. 



On the whole, therefore, it would appear, from the experi- 

 ments detailed in this section 



1. That the nutritive quality, as indicated by the proportion 

 of nitrogen, may be increased in the bulbs of turnips, and pro- 

 bably in other roots, by the use of manures rich in nitrogen 

 though what relation the increase bears to the quantity of 

 nitrogen applied, or to its state of chemical combination, does 

 not appear. 



2. That manures containing nitrogen do not sensibly aug- 

 ment the proportion of nitrogen in the grain of wheat crops to 

 which they have been applied. In some cases they rather 

 appear to diminish it. 



It is to be remembered, however, that there is a great diffi- 

 culty in ascertaining the average chemical composition, espe- 

 cially of a crop of turnips or other roots ; and therefore that, 

 for this and other reasons, our confidence in the above con- 

 clusions ought not as yet to be very decided. 



4. Suggestions for experiments with the carbonate^ nitrate^ 

 muriate , and sulphate of ammonia. 



A perusal of the experimental results embodied in this and in 

 the preceding chapter must already have suggested, both to the 

 theoretical and to the practical reader, many interesting com- 

 parative trials with the salts of ammonia. I shall put down 

 here, however, such as appear to me, in the present state of our 

 knowledge, to be most important. 



1. It is desirable to ascertain more correctly the comparative 

 influence of the different salts of ammonia, applied in equivalent 

 quantities to the same crop, in the same circumstances. 



Of course, this means that the crop experimented upon should 

 be varied until the comparative effects of all these salts on each 

 of our usually cultivated crops is ascertained. 



2. With the same salt applied in different quantities at dif- 

 ferent times all at once, and in successive portions at succes- 

 sive periods. Does the produce increase directly with the 



