Nitrogenous Fertilizers 47 



this reason a rather fictitious value has been fixed upon 

 these products. These products differ very materially 

 from natural guanos, and it is due probably both to the 

 character of the food eaten by the domestic fowl, and to 

 the different methods by which the material is obtained. 

 The birds producing the guanos feed largely upon fish, 

 a highly nitrogenous food, resulting in an excrement 

 richer in this element than that from the domestic bird, 

 feeding largely upon vegetable matter ; and, besides, the 

 former were accumulated in a hot, dry climate, which 

 quickly absorbs the moisture contained in the fresh 

 droppings, thus leaving it in a much drier state than is 

 the case with the domestic product. 



MECHANICAL CONDITION SHOULD BE CONSIDERED 



It will be observed from the foregoing brief description 

 of the chief sources of organic forms of nitrogen, that a 

 very wide variation occurs both in the composition or 

 content of nitrogen in these products, and in the avail- 

 ability of their nitrogen, or rapidity with which, under 

 similar conditions, it is given up to plants. The fact 

 that a substance contains nitrogen in considerable amounts 

 and in an organic form, then, is not a sufficient guide as 

 to its usefulness. Its mechanical condition, or physical 

 form, must also be taken into consideration, and, other 

 things being equal, the tougher and denser the substances, 

 the longer the time required to decay, and hence the more 

 slowly will the material feed the plant. 



AMMONIA COMPOUNDS. See Fig. 1, Plate 1. 



As already stated, nitrogen does not feed the plants 

 in organic forms; it must first decay. The first prod- 



