SOILS AND THEIR PROPERTIES 83 



potash and nitrogen may have their turn in producing 

 satistactory crops. In other words, we go back again to the 

 old proposition that the soil requires a certain balance of 

 ingredients, and, however lacking the soil may have been 

 once upon a time, in one ingredient, if you persist in suppl3'ing 

 this ingredient there may come a time when the chief necessity 

 of the soil is something else altogether. Much harm has 

 been done in the past by the " rule of thumb " man in this 

 respect. In the relatively early days of agriculture, manuring 

 with animal refuse was practised to a large extent. At 

 first this process was good, but it very speedily became over- 

 done ; then the fashion for applying lime set in. At first 

 this was very necessary, because it had been neglected in 

 the past, but that, too, soon became overdone. Then a 

 fashion for the artificial manures, generally phosphatic 

 ones, set in which have often been exhaustive of lime in 

 the soil. To-day the needs of agriculture in populous 

 countries are often more connected with the mismanagement 

 of the past than with any other one factor. In taking up 

 land, therefore, the past agricultural history is always a 

 matter of great importance. The analysis of the soil will 

 assist in checking the history of past good or bad manage- 

 ment. 



* * The Law of Diminishing Returns ' ' is now a recog- 

 nized principle. When a manure is applied in increasing 

 quantities it does not produce a corresponding increase of each 

 idditional amount of manure. The table on p. 84, gives the 

 standard illustration from Rothamsted, in which it will be 

 loted that a steady increase in the amounts of ammonia 

 [compounds soon becomes unprofitable. 



Whether a particular increase of crop obtained from a 



[particular quantity of manure is, or is not, profitable, depends 



[upon the prices of both. Whilst in the above table 89 



►ushels of wheat per acre may be a profitable return for 



500 pounds of ammonium salts, yet if the ammonia became 



iheap and the wheat dear, the 4*5 bushels of wheat as 



returned from 200 pounds of ammonium salts might also be 



very profitable. In other words, intensive cultivation which 



