34 



EXPERIMENTS UPON WHEAT 



the function of any element of manurial plant food in a way 

 that is not possible in the first few years of an experiment^ 

 because of the large reserves of all plant foods contained in 

 ordinary soil. 



Table XIV. shows the nature and quantities of the manures- 

 applied each year to the plots. The mineral manures (by 

 minerals is understood at Rothamsted the phosphoric acid^ 

 potash, magnesia, soda, and other constituents left as ash when 

 the plant is burnt, but not any manure containing nitrogen) 

 are sovr^n before the seed in the autumn, the rape cake and the 

 farmyard manure, and a portion of the ammonium-salts are 

 also supplied in the autumn before seeding, but the nitrate of 

 soda and the greater part of the ammonium-salts are put on 

 as top-dressings in the spring. 



Table XIV.' — Experiments on Wheat, Broadhalk Field. Manuring of 

 the Plots per acre per annum, 1852 and since. 



Notes on the Manures. 



The ammonium-salts consists of a mixture of equal parts of sulphate an(J 

 muriate of ammonia ; 200 lb. supply 43 lb. of nitrogen, equal to the amount 

 contained in 275 lb. nitrate of soda, or 1889 lb. of rape cake. The super- 



