JAMAICA. 



BULLETIN 



OF THE 



BOTANICAL DEPARTMENT. 



~ Vol. VII 

 New Series.] NOVEMBER, 1900. ^^^^ 



MANURING. 



By W. R. Buttenshaw, M.A., B.Sc. 

 Govemment Lecturer in Agricultural Science, Jamaica. 



Plant food is found to be composed of compounds of some twelve- 

 elements. All these, with the exception of three — carbon, hydro- 

 gen, and oxygen, are obtained from the soil. A fertile soil contains 

 compounds of all these elements, while an exhausted soil is deficient 

 in one or more. The elements that are liable to be deficient are Nitro- 

 gen, phosphorus, and potassium. Manuring, therefore, aims at return- 

 ing to the soil substances containing one, or more, of these three 

 elements. 



The fertility of a soil depends, however, not only upon the presence 

 of these substances, but also upon the state in which they are 

 present. To be available to the plant they must be in such a state 

 that they can be dissolved, either by the water in the soil, or, by the 

 acid sap that is excreted by the root-hairs of plants. The small amount 

 of plant food which is in this available state would ver}" soon be ex- 

 hausted, were it not that changes are constantly occurring in tne soil, 

 which result in the conversion of the unavailable, or dormant, plant 

 food into an active or availab.e form. These changes are greatly aided 

 by the thorough cultivation of the land^ which allows the atmosphere to 

 exert its powerful influence, as they consist for the most part in render- 

 ing insoluble compounds more soluble by their union with oxygen. 



Unfortunately, this conversion is unable to keep pac^ with the re- 

 moval of available plant food by crops. The cocistant removal of pro- 

 duce from the land causes the supply of available forms of one or more 

 of the elements to fail, whereupon the land is said to to be exhausted. 

 But it must be remembered that it does not follow that these three- 

 elements are entirely absent ; they may be present in an unavailable 

 state. 



A clear idea of the effect which the removal of produce has upon 

 the fertility of the land will be obtained, if a comparison be made be- 

 tween natural vegetation and man's cultivation of the land. In the 

 formpr case, the plants that grow on the land are either eaten bv 

 animals, or are allowed to die and decay where they grew. Whether 



