214 PHOSPHATE OF AMMONIA. 



directly to the growth of plants. It cannot be doubted that the 

 largest proportion of the organic matter of the soil is derived 

 from the air, through the instrumentality of vegetables that 

 have lived and died upon it. But does this organic part of the 

 soil serve no direct purpose in feeding and nourishing the 

 plant ? That it should do so is quite consistent with the fact of 

 the plant's drawing a large proportion of its carbon from the 

 air. But this question would be helped towards a satisfactory 

 solution if experiments were made. 



a With carbonate of ammonia in different proportions, 

 applied in different ways, and under different circumstances. 



b With humate of ammonia alone, and in comparison with 

 the carbonate of ammonia, upon the same crops, and in the 

 same circumstances. These would show whether and to what 

 extent the humic acid modified the action of the ammonia. 



c With humate, in comparison with sulphate or muriate of 

 ammonia. These would show how far the mineral sulphuric or 

 muriatic acid acted in a similar way with the humic acid 

 how far the presence of the organic acid did or did not promote 

 the more rapid and healthy growth of the plant. 



Though the results obtained by means of these comparative 

 experiments may not be wholly free from doubt and ambiguity, 

 yet they will form a valuable basis for future field inquiries. 



6. Suggestions for experiments with the phosphate of ammonia, 

 with the ammoniacal phosphate of soda , and with the ammo- 

 niacal phosphate of magnesia. 



1. The phosphate of ammonia described in the preceding 

 chapter is likely to prove a very powerfully fertilising substance. 

 Being capable of supplying both nitrogen and phosphorus to the 

 plant, it may be expected to produce a very sensible action upon 

 its growth ; and as it may be manufactured easily, it is desirable 

 that field experiments should be tried with it applied alone. 



a In different proportions, at different seasons, and to different 

 plants. 



b In comparison with the other salts of ammonia, and espe- 

 cially with the sulphate, under similar circumstances. 



