840 ANNUAL REPORT OF THE Off. Doc. 



swamp aud lake muck. This muck furnislies nitrogen us well as 

 the much-needed organic matter. These phosphates have also given 

 good results on the "hammock lands." 



ALUMINA AND IRON PHOSPHATE GUANOS. 



As has been already mentioned, there is a large class of phosphates 

 which are derived from the dung of birds and sea fowls, which go 

 under the term of guano. These phosphates have more the appear- 

 ance of earth than of organic products. As originally formed, 

 of course, these were mostly phosphates of lime, but through the 

 action of the water, in conjunction with Hie rock and soil charac- 

 teristics of the islands, the lime has been replaced by alumina and 

 iron. Most of the phosphates from the islands off the coast of South 

 America and from the West India and Caribbean Islands belong to 

 the alumina and iron class. 



They are popularly known under the name of the island on which 

 they are found, and the principal ones which are met with in agri- 

 cultural literature aud trade are as follows: Alta Vela, Caribbean, 

 Cuban and Kedunda phosphates or guanos, besides the Mona Island, 

 Navassa and Orchilla guanos already mentioned. 



THE USE OF PHOSPHATES. 



There seems to be but little doubt as to the need for the appli- 

 cation of phosphates when the amount that is being taken out of 

 the soil annually by crops is considered. It has been seen from 

 the matter on the preceding pages that there is an abundant supply 

 of phosphoric acid to draw from, and in quite a variety of forms, 

 so that it would seem possible to be able to comply in this respect 

 with almost every requirement of the soils and crops w^hich might 

 be presented. While most farmers seem to be aware that there is 

 a variety of sources of phosphates, yet they have not come to give 

 that consideration to the other phases of the subject as would 

 seem desirable in order that the different pliosphates might be used 

 most intelligently or with more profit. In this connection, the 

 following questions immediately arise in the minds of the farmer: 



1st. Under what conditions is it possible to essentially increase 

 the returns from the soil by the application of phosphates? 



2d. What kind of phosphates shall be used? 



3d. How shall it be used or applied? 



4th. How much shall be used? 



These are all natural questions and ones to which every farmer 

 could well give more study. The first point to study in the con- 

 sideration of the question of the application of phosphates is the 



