TWELFTH ANNUAL REPORT ' 35 



factors influence the soil, and a most intelligent and thorough 

 understanding and systematization of them is necessary to 

 obtain the best results, for at a given time any one of these may 

 become a controlling factor in the production of a crop. Because 

 of the more or less crude methods of cultivation in use through- 

 out the Archipelago, it has not always been easy to determine 

 whether the chemical or the cultural elements are the limiting 

 factors. 



Hundreds of soils from the more important agricultural regions 

 of Luzon and other islands have been analyzed, and show that 

 diff"erent sections vary in their chemical and physical composi- 

 tions. Eventually, these analyses will form a basis for more 

 extended work on methods of fertilization and production of 

 special crops adapted to the different localities. This informa- 

 tion in conjunction with data concerning the crops grown may 

 give information regarding the needs of the soil and the kind 

 of crops adapted to a particular region. 



This Bureau has been able to supply information concerning 

 the potential fertility of the soil, ease of plowing, drainage, and 

 consequent effect upon bacterial development. We have been 

 able to predict the soil constituents that would be exhausted in 

 the course of crop production and to indicate the proper fertilizers 

 as well as the abundant elements of plant food that would not 

 need to be supplied by fertilization. 



In the absence of more authentic data, it is possible to judge 

 by an examination of the vegetation whether important crops, 

 such as coconuts, abaca, maguey, rubber, and tobacco, will thrive 

 in a particular locality. Where certain species of plants are 

 dominant, there is a prolonged dry season ; where the rainfall is 

 continuous, more vigorous species crowd them out. Full data 

 are not yet available on the exact types of vegetation indicating 

 the probable success or failure of all of these crops, but in general 

 the presence or absence of certain native species in a given region 

 well indicates what cultivated plants may be expected to thrive 

 and what in all probability will not thrive. From a commercial 

 standpoint, the importance of this is very great, for no individual 

 should risk the loss of money in the establishment of plantations 

 in regions where it is practically certain that his particular crop 

 will not thrive. 



57. Fertilizers. — In recent years the exploitation of the guanos 

 of the Islands has been attempted, and the Bureau has been called 

 upon to analyze and give necessary information concerning their 

 possible commercial value. Data and analyses concerning a 

 considerable number of guanos have been published in order to 



