194 CROPS GROWN IN ROTATION 



with hardly any development of bulb. The crop, indeed, fell 

 away to nothing as soon as the manure was discontinued ; it 

 was less than 8 per cent, of the crop on the manm-ed plots 

 dm^ing the first foiu' com'ses, and it has fallen to about half 

 that quantity dm-ing the last five courses. Swedes have thus 

 very little power of growing upon the reserves of nutriment 

 in the soil, and they are almost wholly dependent upon an 

 immediate supply of manure. 



The barley has yielded on the unmanm^ed plots 16 bushels 

 of grain and 11 cwt. of straw per acre dm^ng the last five 

 courses. This amounts to about 59 per cent, of the yield 

 on the manured plots in the same years, whereas for the first 

 four courses the yield on the unman ured plots was about 

 70 per cent, of that of the manured plots. As compared 

 with the corresponding plots in the same years in Hoos 

 field, where barley is grown continuously, the yield of barley 

 has been much better maintained when grown in rotation. 

 On the Hoos field in the later years the production of the 

 unmanured plots has fallen to 27 per cent, of that of the 

 manured plots, while the rotation barley on the unmanm'ed 

 had only fallen to 59 per cent, of that on the maniued plots, the 

 same years being compared in each case. 



On the Rothamsted land it is not found desirable to grow 

 clover every four years, so only six clover crops have been 

 taken during the course of the experiment, beans having been 

 substituted in the other cases. On these leguminous crops the 

 absence of manure has had a very marked effect ; the produc- 

 tion, which was nearly 60 per cent, of the manured plots in the 

 earlier courses, has fallen to less than 41 per cent, in the later 

 ones. Thus the leguminous crops are much more affected by 

 the cropping out of the land than is the barley. 



The wheat is better able to resist the deterioration of the 

 fertility of the soil than any of the other crops are. The 

 average production dm-ing the later courses has been 26 '2 

 bushels per acre on the unmanm'ed plots, as compared with 

 11*6 bushels per acre on the unmanured plot in Broadbalk 



