■26 EEPORT OF OFFICE OF EXPERIMENT STATIONS. 



communities. The work will be planned and directed by the station, 

 and the results can be interpreted by the man locally in charge. 

 The work for the present will be largely on better methods of cul- 

 tivation, rotation, and the introduction of neAv crops. 



PORTO RICO STATION. 



The office and laboratory building provided from insular funds 

 \vas occupied and the installation of the equipment completed during 

 the past year. The building has proved a model of comfort and 

 convenience. The station and its work are being more appreciated 

 each succeeding year, if the increased number of visitors, the growth 

 of correspondence, and requests for advice and assistance are any 

 i^riterion of the estimate placed upon it. While, of necessity, much 

 W'ork is done that is of an elementary and demonstrational character, 

 efforts are continually being made to draw the work into more defi- 

 nite lines relating strictly to tropical conditions, with a view to de- 

 termining some of the fundamental principles underlying a rational 

 system of tropical aginculture. 



One of the lines to which especial attention is being paid is soil 

 investigations. The climatic conditions in the Tropics have a peculiar 

 effect on the soils. It was shown in the previous report that certain 

 anaerobic bacteria tend to accumulate in the soil, and the products of 

 their activity are detrimental to plant growth. It has been found 

 that disinfecting the soil with chemicals, burning, or fallowing tends 

 to correct these injurious conditions, and the station is working on 

 cheap and efficient methods of partial soil sterilization. The physi- 

 ologist of the station, who discovered that the areas designated as 

 ''sick soils" contained abnormal amounts of butyric acid resulting 

 from an accumulation of anaerobic bacteria in the soil, has continued 

 his investigations, studying especially the role of protozoa in soils and 

 methods for the economical disinfection of soils. The experiments 

 on disinfection were conducted with soils that had become so infested 

 with butyric-acid organisms as to render the cultivation of lilies im- 

 possible. A number of disinfectants were tried and the best results 

 were obtained with carbon bisulphid and chlorid of lime. The re- 

 sults indicate that chlorid of lime is one of the best and cheapest soil 

 disinfectants known. 



The chemical department during the past year carried out a large 

 amount of analytical work on new varieties of sugar cane, waters, 

 limestones, guanos, and other fertilizing materials. The research 

 work was chiefly devoted to studies on soils and plant nutrition. 

 Among the subjects of soil studies were the formation of calcareous 

 hardpan, injury by alkaline waters, lime requirements of soils, etc. 

 A larffe amount of work has been done on the causes and means for 

 correction of the chlorosis of pineapples in certain districts of the 



