SOILS 



47 



Chemical Analyses. 



An exact chemical analysis of a soil may be useful as 

 showing any deficiency in plant food, but it is not generally of 

 great practical use, because it does not show in what state the 

 elements exist ; — whether suitable for plant food or not. 

 Analyses may, however, show the available amounts of the 

 plant foods present by the use of a 1 per cent solutioD of 

 citric acid (Dyer's method). This is purely empirical, but has 

 been found to give good results. Mechanical analyses show 

 the sizes of the particles composing the soil which are usually 

 given in six grades. Analyses of three classes of soils at the 

 Coimbatore Central Farm are given below. They represent 

 " dry red," " garden " and " black " soils respectively. 



