234 PERUVIAN GUANO, ETC. [chap. 



soluble in water, being combined with the ammonia 

 and the potash and soda also present in small 

 quantities. 



Similar detailed analyses are not available for 

 poorer grades, but it may be taken as a general 

 rule that the lower the percentage of nitrogen, the 

 less of it will be found in a soluble form, and the 

 more insoluble will the phosphoric acid compounds 

 have become, so that the richest guanos are also 

 the most readily available for the plant. It is also 

 characteristic of a good guano, and to this much of its 

 value as a choice fertiliser is due, that the compounds 

 of nitrogen present are very varied and require differ- 

 ent series of bacterial changes in the soil before they 

 become available, so that the crop is fed steadily and 

 continuously. 



It is this property and the fact that guano is naturally 

 a well-balanced manure, rich in phosphates as well as 

 nitrogen, and containing also a small proportion of 

 potash, which makes guano so popular. It is essentially 

 a safe manure, applicable to all crops, and not requiring 

 the skill in its adjustment to the land or the crop which 

 is necessary with the more active single manures like 

 nitrate of soda, etc. Again, coming into action con- 

 tinuously and equably, it is more calculated to yield 

 produce of high quality than more concentrated 

 manures ; it is therefore specially suited for fruit and 

 similar valuable crops. As a natural consequence of 

 these advantages the good Peruvian guanos are always 

 somewhat dearer than other manures when valued on 

 a unit basis, the extra price representing partly the 

 value of this natural blending and partly the long 

 farming tradition of the excellence of guano, which was 

 the earliest of the concentrated manures to find a large 

 sale in this country. 



