186 



SOILS AND MANUEES 



casually for several years. The object is, generally, to 

 try the effects of nitrogenous, phosphatic and potash 

 manures and the different combinations of the same. By 



10 x 20 

 20*40 



(nearly f 



Phosphate Potash Nitrogen 



FIG. 25. 



comparing the results with each other and with that 

 obtained on an unmanured piece, it is generally possible 

 to determine what is required. This experiment is com- 

 monly known as the " eight-plot test," because that is 



