FERTILITY 



173 



in some degree, to the rate at which the plant food is con- 

 verted from the non-available to the available state. 



The yield of wheat, barley, hay and roots (mangolds) 

 in 1907, and the estimated quantities of nitrogen, phos- 

 phoric acid and potash contained in the same are given 

 in the following table: 



YIELD OF CROPS FROM THE CONTINUOUSLY UNMANURED PLOTS AT 

 ROTHAMSTED AND THE QUANTITIES OF PLANT FOODS IN THE 



SAME. 



PER ACRE. 



