CHAPTER X 



EXPERIMENTS UPON CROPS GROWN IN ROTATION, AGDELL FIELD 



I. The Unmanured Plots. 

 II. Effect of the Manures. 



III. The Effect of the Growth of Clover or Beans on the succeeding Crops. 



IV. Effect of Manurial Residues on subsequent Crops. 



, V. Gain or loss of Manurial Constituents to the Land. 

 Practical Conclusions. References. 



THE Agdell field, which was put under experiment in the year 

 1848, differs from the other Rothamsted fields in that it is 

 farmed on a four- course rotation of Swedes, barley, clover (or 

 beans) or fallow, and wheat, instead of growing one crop con- 

 tinuously. It is divided into three main plots, one of which (O) 

 has received no manure, the second (M) mineral manures only 

 (superphosphate alone in the first nine courses), and the third 

 (C) a complete manure, containing the same minerals, but also 

 nitrogen in the form of rape cake and ammonium-salts. The 

 manures are applied to the Swedes only, the other three crops 

 of each course being grown without manure. Each of the 

 three plots was originally subdivided into four, so as to obtain 

 the following comparisons : (1) Half the plots carried clover 

 or beans as the third crop of the course, and half the plots 

 were bare fallow. This showed the effect of introducing the 

 leguminous crop into the rotation, as compared with the bare 

 fallow. (2) From half the plots the root crops grown in the 

 first course were carted ; on the other half the roots were eaten 

 on the land by sheep ; or rather, since the land is unsuited to 

 winter folding, the roots were chopped up and ploughed in. 

 This showed the effect on the succeeding crops of barley, etc., 

 of the return of a root crop to the land by folding. 



In 1903 the second division was abolished, and since then 

 the three plots have been divided into two only, clover and 

 fallow respectively in the third year : the roots are carted from 

 all plots. Table LXIV. shows the mean results for the five 

 courses 1884-1903 and the two courses 1904-1911. 



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