156 SOIL CONDITIONS AND PLANT GROWTH 



TABLE LX., VARIATION IN SOIL DUE TO WASHING OR FLOODING. 



The characterisation of soil types is sufficiently effected by me- 

 chanical analysis and determinations of calcium carbonate and organic 

 matter. A representative set of soils should, however, be subjected to 

 chemical analysis, the clay fractions being, if possible, broken up by 

 ammonium fluoride and analysed completely. Soils about which 

 precise information has been obtained by manurial and other trials 

 should be very completely examined in order that they may serve as 

 standards in the analysis of other soils from the same area. 



The problem set by the farmer is wholly different. He does not 

 want to know to what type his soil belongs, but how he must manure 

 it, etc. If the analyst has an adequate knowledge of the soil type and 

 the locality he can readily ascertain in what respects the soil differs 

 from the type, and then, from the known results of manurial and other 

 trials on that type, he can give the information wanted with a reason- 

 able degree of probability ; otherwise his report can only be a matter 

 of guesswork. In short, the farmer's problem can be satisfactorily 

 solved, and the manurial trials fully interpreted, only when a com- 

 plete soil survey has been made. 



The analyst must consider the soil from three points of view: (i) 

 its physical properties, especially those relating to the ease of move- 

 ment of the soil water ; (2) its store of plant food, actual and potential ; 

 (3) the rate at which potential food can be converted into actual food 



