72 CHEMICAL FERTILIZERS 



1 6 % of ammonium urate, 17 % of ammonium oxalate, 6 % 

 of ammonium phosphate, and 11% of ammonium magnesium 

 phosphate. All these compounds are very uncommon, and are 

 not found in any fertilizers other than guano. The phosphate 

 present is partly there as potassium phosphate, but mostly 

 exists as a calcium compound. Where the guano has been 

 leached out by water, the percentage of nitrogen is very low. 

 In some cases the percentage of calcium phosphate is also 

 low, as well as the nitrogen, owing to the admixture of various 

 quantities of sand and pebbles, and in some varieties this 

 useless material may be present up to 20 %. Modern guano 

 seldom contains more than 10 % of nitrogen ; those qualities 

 recently imported contain nitrogen 2-11 %, phosphates 

 I 5~4 % an d potash from i to 4 %. Some of the guanos 

 now being excavated are of quite recent deposit, and con- 

 tain feathers and other undecomposed material. The sea 

 birds still inhabit their old haunts off the coasts of Peru 

 and elsewhere, and are still depositing dung and waste sub- 

 stances for producing guano. Owing, however, to the smaller 

 amount of decomposition, there is far less ammonium carbon- 

 ate, and consequently less of the characteristic guano odour. 

 In the case of phosphatic guanos, which have had most of 

 their soluble material washed away, neither the nitrogen nor 

 the phosphate have the same value as those materials in a 

 high grade nitrogenous guano. The phosphate in these 

 washed-out guanos is practically all tri-basic calcium phos- 

 phate, and is only superior to that of bones so far as it may be 

 in a finer state of division. 



The composition of all guanos is so variable that without 

 an analysis of a given specimen no definite value can be 

 attached to the sample in question. 



When applied to the soil, the ammonia compounds of 

 guano are rapidly fixed, and soon undergo the process of 

 nitrification. Guano forms a very complete manure of a 

 quick-acting character, and, being in a fine, dry powder, has 

 the added advantage of easy distribution. 



Bones. One of the earliest of the phosphatic manures 

 which was used in Great Britain was ordinary bones, which at 



