MANUAL FOR SUGAR GROWERS. 



23 



The weight of an acre of soil to a depth of nine 

 inches is about 3,000,000, or 3,500,000, pounds ; it 

 will thus be seen that even a small proportion of 

 plant-food will amount to a very large weight when 

 calculated to pounds per acre ; and this is important 

 in considering chemical analyses, where the propor- 

 tion of various constituents is often stated in parts 

 per one hundred ; thus one per cent, would represent 

 30,000 or 35,000 pounds, or about sixteen tons per 

 acre to a depth of nine inches. The quantity of solu- 

 ble matter shown by chemical analysis may often 

 seem to be extremely small, and very accurate 

 methods must be followed if trustworthy results are 

 to be obtained. The following table gives some idea 

 of the amounts of plant-food soluble in dilute acid, 

 in the manner already alluded to, in the case of cer- 

 tain soils under cultivation in sugar-cane. 



Mineral Plant-food per Million Pounds of Soil, or 

 PER Acre Three Inches Deep, Soluble in Dilute 

 Acid, 



Mineral substance. 



Silica (SiOo) 



Lime (CaO) 



Magnesia (MgO) 



Oxide of Iron (Fe203) 



Potash (KoO) 



Phosphoric acid 



(P2O5) 

 Sulphuric acid (SO3) . 



n. m. IV. V. VI. I VII. vin, 



1010 6995 1323 1874 

 2538 4266 4420 4083 



320 1203 



800] 45 



38 256 



28 



500 



210 



80 



65 36 



1934 



144 



61 



1776 



3810 



760 



120 



33 



37: 70 



1121 



5415 

 980 



? 



'27 



18 



IX. 



1028 ? 

 100000 400000 

 100000 400000 



3650 j 3500 

 169] 267 



185 



87 



L, n., and m., volcanic soils, Moutserrat, W. I. IV., V., and VI., volcanic 

 soils, Antigua, W. I. VTI. and VIII., sedimentary, non-calcareous soils, An- 

 tigua, W. I. IX. and X., calcareous soils, Antigua, W. I. 



Now, the undecomposed portion of the soil usu- 

 ally contains a very aj)preciable amount of plant- 



