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 sown 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, Broadbalk 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 and 

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

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



