THE SOIL 



57 



Rotation I. Rotation II. 



Turnips Turnips 



Barley Barley 



Clover (or beans where clover failed) Fallow 

 Wheat Wheat 



The first is termed the legume rotation, the second the 

 fallow rotation. Both rotations are arranged so that 

 complete fertilization can be compared to no treatment. 

 The complete fertilization consists of the addition of 

 essential plant food elements in the form of common 

 commercial fertilizers. Nitrogen, phosphorus, potas- 

 sium, magnesium, sodium and sulphur are included, in 

 the form of ammonium sulphate, acid phosphate, potas 

 sium chloride, etc. The fertilizers are applied once in 

 four years (for the turnip crop). The experiment has 

 been carried on for sixty years, the results appearing in 

 table XIII. 



TABLE XIII. Rothamsted Experiments, Agdell Field. 



This is perhaps the world's best evidence on the food 

 requirements of plants. On the unfertilized fields the 

 crop yields steadily decreased. On the fertilized fields 

 the yields have been maintained at a high average, the 

 turnips averaging during the last 20 years of the 60- 



* Beans grown when clover failed. 



