212 THEIR ACTION ON THE QUALITY OF A CROP. 



ammonia as the nitrate of ammonia, produce an equal effect? 

 These are curious questions, neither of which will probably 

 be answered in the affirmative when careful field experiments 

 are made, but the investigation of them may conduct us to 

 important practical truths. 



10. Do the salts of ammonia add to the nutritive quality 

 of a crop ? This question is to be solved by experiments in 

 feeding with the crops raised by means of the salts of ammonia, 

 and by analysing them in the laboratory. The former method 

 is in the power of the practical man and is deserving of much 

 attention. 



This general question includes several subordinate ones, such 

 as 



a Do they add to the richness of grain in gluten, as some 

 have said ? This we have elsewhere seen to be very doubtful ; 

 but the question is by no means decided. 



b Do they increase the feeding quality of root-crops and 

 cabbages? The comparative feeding quality is represented 

 pretty nearly by the proportion of nitrogen contained in the 

 crops we raise, and this proportion appears capable of material 

 increase by the use of the salts of ammonia, and of rape-cake. 

 The details of Mr Lawes' experiments upon two crops have 

 been given in a preceding section. 



c Is the more succulent grass of fields, top-dressed with salts 

 of ammonia, more nutritious also, weight for weight ? This is 

 a question which the feeder, as well as the chemist, is required 

 to solve. 



d As to the function of the ammonia, does it directly supply 

 nitrogen to the crop at all, or does it act in some other way ? 

 This question is more purely theoretical, though of great prac- 

 tical consequence. 



11. In conclusion, I may suggest the importance of com- 

 parative experiments between the nitrates of potash, &c., and 

 any of the salts of ammonia. If they be applied in equivalent 

 quantities, or two equivalents of the one against a single equi- 

 valent of the other, accurate duplicate experiments made upon 

 any crop will afford valuable data for the solution of existing 

 theoretical and practical difficulties. 



