PHILIPPINE GUANO. 
By ALvin J. Cox. 
(From the Laboratory of General, Inorganic and Physical Chemistry, 
Bureau of Science, Manila, P. 1.) 
In any agricultural undertaking the total composition of the 
soil must always ultimately be taken into account, for from the 
soil under normal conditions certain elements of plant food are 
derived. Some constituents become exhausted after years of 
cultivation and the soil requires fertilization in order to make 
it productive. This is especially true of the elements nitrogen, 
phosphorus, and potassium. When the percentage of any one 
of the elements of plant food existing in the solid falls below 
0.1, the productive capacity may be questioned. Up to the 
present time there has been very little fertilizer used in the 
Philippine Islands. In some places the soil has been seriously 
exhausted by years of cultivation, and its productivity can not 
be restored without fertilization. 
The maintenance of the productive capacity of soils has been 
a subject of the greatest concern and interest from the earliest 
historic times, but the use of commercial fertilizers is not old. 
Sodium nitrate was first imported into England about 1830 and 
natural guano ten years later. 
With the agricultural development of the Philippine Archi- 
pelago the attention of the agriculturist and scientist has been 
turned to the subject of fertilizers, and it may be of interest to 
discuss the question of Philippine natural fertilizers—the phos- 
phatic guanos of the Islands. These consist of the excreta of 
sea fowls and other birds, bats, and marine animals, with more 
or less bone and animal matter furnished by dead bodies, and 
are found in large quantities in some places, mainly on small 
islands and in numerous limestone caves. That from caves is 
usually bat excrement. Deposits of bat guano have been dis- 
covered on a great many of the islands, chief among which are 
Marinduque, Guimaras, Luzon, and Mindoro; and some of these 
have been located and recorded. The deposits in some of the 
caves are reported to consist of one or more thousands of tons. 
Probably as yet not over 1,000 tons of guano have been mined 
in the whole Archipelago. In a few instances considerable quan- 
tities of bat guano have been removed from church towers. 
Guano is somewhat granular in appearance and is usually a 
brown or grayish powder, but the color varies so much that it 
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