114 



Lime Potash Phos. Acid Nitrogea 



Island per cent. per cent. per cent. per cent. 



Oahu -380 -342 -207 -176 



Kauai 418 309 -187 -227 



Maui -396 '357 '270 -388 



Hawaii '185 -346 '513 '540 



With such fertile soils, and with perfect control of the supply of water 

 no wonder that ten tons of sugar have been made per acre. 



Soils are only disintegrated rocks mixed with vegetable debris and 

 more or less charged with micro-organisms, through whose agency the 

 food for plants is rendered available It is not only necessary that an 

 abundance of plant food exhibited by chemical analysis be present, but 

 it must be in an available form. The more finely divided the rock 

 particles, the larger the quantity of available food, the greater the sur- 

 face areas of its particles, and therefore a large increase in surface 

 tension which gives an increased capacity for holding moisture. There- 

 fore the mechanical condition of a soil is frequently of more importance 

 than a chemical analysis. Formerly a soil was regarded as being a 

 mass of inert matter whose ingredients were rendered soluble by the 

 action of air, water and chemicals. Ttds view has given way to a know- 

 ledge recently gained by scientific investigations, that all fertile soils 

 are swarming with microscopic organisms which are essential to the 

 proper elaboration of the food materials in a soil for plant use 



Hence a thorough investigation of a soil involves a chemical analysis, 

 a mechanical separation of its particles, a study of its physical proper- 

 ties, and a microscopic research for its bacterial content. (^) 



A chemical analysis will give its contents of silica, iron, alumina, 

 lime, magnesia, potash, soda ; phosphoric, sulphuric and carbonic acids ; 

 chlorine, nitrogen, etc, The total quantities of each of the above solu- 

 ble in the selected solvent are given, but no definite methods has yet 

 been devised by which a knowledge of the immediate availability of 

 these ingredients may be obtained. Chemical analysis has, however, a 

 high value in the hands of a trained chemist. 



The particles of soils vary greatly in size as well as in constitution, 

 and a knowledge of the mechanical formation of a soil frequently throws 

 a flood of light upon its relation to heat and moisture, as well as sug- 

 gestions upon its cultivation. It has been conventionally agreed that 

 all particles in a soil between 1 and 2 mm* in diameter shall be called 

 fine gravel ; between '5 and 1 mm coarse sand ; between '25 and '5 

 mm., medium sand; between .1 and .25 mm., fine sand; between .05 

 and .1 mm., very fine sand, between .01 and .05 silt between .005 

 and .01 mm., fine silt and .0001 and .005 mm., clay. Such an 

 analysis describes the textures of a soil and determines the crop 

 which should be grown thereon, by comparing the water-carrying capa- 

 city of the soil with the water requirements of the crop. To illustrate, 

 the more clayey the soil, the greater its carrying capacity, and the 

 nearer the approach to pure sand, the more droughty it becomes. 

 Grasses, in which sugar cane may be placed as a gigantic specimen, re- 

 quire at least 25 per cent of moisture continually in the soil for best 



(3) A recognitiou of these points is essential if scientific and progressive agri- 

 culture is to prevail. F.W. 



* Note— mm., millimetre = .0393 of an inch. 



