280 cox. 



potassium and calcium are derived. It is fortunate tliat the inorganic 

 constituents are not in a constant state of combination but rather are 

 distributed between the soil-moisture and the undissolved- substance in 

 contact with the solution in a state of equilibrium according to known 

 laws, else the plant food would soon be esliausted. ^Vlien a portion of 

 the inorganic constitutents is withdrawn from the soil-moisture b}^ the 

 growing plant, more soluble salts from the soil begin to go into solution 

 and finally when the soluble salts approach exhaustion, probably more 

 begin to form from the practically insoluble ones. However, it is not 

 my intention to discuss further the exceedingly interesting question of 

 how these go into solution or how the mineral plant-food supply is main- 

 tained. 



The organic fraction of the soil, which is the source of a part of the 

 food of plants, may consist of almost any kind of animal or plant 

 remains and the products of their degradation and decomposition, and 

 is usually the result of the growth, degradation, and decomposition of 

 organisms and vegetable matter on the surface of the ground or of animal 

 matter (manure) artificially supplied. A part of the organic matter 

 often markedly shows the original plant fiber, while the other portion 

 no longer retains any of the original structure but has become a black, 

 characteristic product, called humus, which surrounds the soil particles. 

 Soils which contain a large quantity of humus are usually dark in color, 

 but organic matter does not always impart a black color and black soils 

 are not necessarily high in organic matter, the color being determined 

 rather by the soil particles themselves. 



The suitability and the maintenance of the productive capacity of soils has 

 been a subject of the greatest concern and interest from the earliest historic times. 

 In the United States the study of soils adapted to the various crops has been 

 taken up very carefully. Extensive studies have been made by the Bureau of 

 Soils of the United States Department of Agriculture, and others, of the soils 

 suitable for the production of the great cereal crops, of the cotton soils of the 

 Gulf States, of the rice soils of Arkansas and Louisiana and of those suitable for 

 sugar, tobacco, fruit, etc. The Bureau of Science has already published a con- 

 siderable number of data on the soils suitable for the growing of sugar in the 

 Philippines,^ but veiy few have been segregated concerning those best adapted 

 for the cultivation of rice, both mountain and lowland, coconuts, hemp, coffee, 

 pineapples, sweet potatoes, peanuts, and other crops of the Archipelago. Some 

 of these products, like coconuts and hemp, reach the highest development only 

 on certain kinds of soils, and in time we hope to establish the type.- 



' Walker, H. S., The Sugar Industry in the Island of Negros, Department of 

 the Interior, Bureau of Science, Manila, 1910. 



^Copeland, This Journal (1906), 1, 6, shows that a considerable supply of 

 water must constantly be at the disposal of the coconut, or it will protect itself 

 against injurious desiccation by a partial suspense of its vitality; and Walker, 

 ihid, 60, shows that in view of the large amount of water necessary to the life of 

 coconut trees they grow better in very porous sandy soil rather than in one 

 from which water and soluble nutriment can only be taken up with difficulty. 



