14 The Rothamsted Experiments. 



years, and the arrangement was the same for the fourth 

 year, save that on Plots 2 and 4 the quantities of sulphate 

 of potash were reduced from 3001b. to 2001b., and of 

 sulphate of soda from 2001b. to lOOlb. per acre. In the 

 fifth and sixth seasons the crop was grown without any 

 fresh application of manure. 



The object of experiment 1 was to ascertain the state of 

 productiveness of the land without any manure, and so to 

 provide a standard by which to compare the effects of the 

 different manures. Experiments 2, 3, 4, 6, and 7 were to 

 determine whether a specially mineral, nitrogenous, or 

 carbonaceous manure, or some combination of these, is the 

 most effective, and experiment 5 would indicate whether 

 increase of crop can be profitably obtained by a cheap 

 " artificial" manure containing a large proportion both of 

 nitrogen and phosphates. 



The results of the six years' experiments (1856-61) as 

 collected in a series of tables may now be discussed. It is 

 noteworthy that after the land had been well dunged, and 

 had grown a crop of beans, the greatest increase, especially 

 of grain, obtained in the first year was where the manure 

 was the most nitrogenous. Thus, the ammonia-salts alone, 

 the guano, and the rape cake each gave 4 to 5 bushels 

 increase of dressed corn ; whilst the mineral manure, and 

 the mineral manure and ammonia-salts together, gave only 

 about one bushel. The ammonia-salts alone also gave 

 rather more increase of straw than any of the other 

 manures, more even than the mixed mineral manure and 

 ammonia-salts together. The produce of the unmanured 

 plot in the second and succeeding years showed, however, 

 that the condition of the land had then become reduced ; 

 and it is therefore from the average results of each of the 

 different manures taken over a series of years that it is 

 most convenient to judge of the character of the exhaustion 

 induced by the growth of the wheat crop in that particular 

 soil. 



