122 Conservation of the Fertility of the Soil, [may, 



supply of nitrogen will be required, either in the form of 

 nitrogenous fertilisers for the root and wheat crops, or of 

 purchased feeding-stuffs to enrich the dung. Nor will it be 

 sufficient, and this is a very important point, merely to add 

 as much nitrogen as is taken away from the land in the 

 increased corn crops ; we have to add enough to get the land 

 into much higher condition, and this means greater wastage 

 at every stage. We have seen in the case of the Rothamsted 

 plot receiving dung how great the wastage becomes when a 

 large amount of dung is put on the land every year, and 

 though the losses in this case are excessive, they will always 

 become greater at an ever-increasing ratio the higher the 

 condition of the land. It is another example of the well- 

 known law of diminishing returns ; the first addition of 

 manure produces the best effect ; each succeeding application 

 produces a smaller increase in the crop till at a certain point 

 nothing further is gained, however much manure is put on. 



We may conclude, then, that with every system of farming 

 a certain position of equilibrium will be reached (viewed over 

 a term of years long enough to smooth out seasonal effects) 

 when the natural recuperative agencies and the additions of 

 fertilising material in the manure are balanced by the removals 

 in crops and stock and the inevitable waste. The higher the 

 level of production, the greater will be the waste, and, in 

 consequence, the additions of fertiliser must be doubly in- 

 creased to maintain the balance. How high a level of pro- 

 duction can be profitably maintained is determined by the 

 prices that rule for the crops, but there will always come a 

 limit when the production can be no longer increased by 

 additions of fertiliser except at a loss; at such a stage it is 

 only the introduction of improved varieties or some variation 

 in the methods of cultivation inducing a better utilisation 

 of the fertiliser which will still profitably increase the produc- 

 tion per acre. 



On examining the variations in farming systems in different 

 parts of the country, it will be found that farmers do instinc- 

 tively adapt their expenditure on fertilisers (including feeding- 

 stuffs), and, therefore, their level of production to the 

 magnitude of the returns they can get for their produce; 

 one man will have a large cake bill and spend 40s. per acre 

 on artificial fertilisers during his rotation ; he can maintain 



