114 



The Rothamsted Barley Experiments. 



nitrogen within the soil, and of its comparatively great power 

 of exhausting it. 



The experiments on barley in four-course rotation (turnips, 

 barley, clover or beans, wheat) were commenced in Agdell 

 Field in 1848, and have been continued ever since. The area, 

 of about 2J acres, was divided into three equal portions. 

 One-third has been left entirely unmanured from the outset ; 

 one-third has been manured with superphosphate of lime 

 alone once every four years that is, for the turnip crop 

 commencing each course ; and one-third, also for the turnip 

 crop only, with a complex manure, consisting of superphos- 

 phate of lime, salts of potash, soda, and magnesia, sulphate 

 and muriate of ammonia, and rape cake. From half of each 

 plot the whole turnip crop (roots and tops) was removed ; on 

 the other half the roots were consumed on the land by sheep, 

 and the uneaten leaves spread and ploughed in. In the first 

 course, clover was grown as the third crop ; but in the second 

 to the sixth courses, instead of clover, half of each plot was 

 sown with beans, and the other half left fallow. The average 

 produce of turnips per acre over the first five courses (the 

 crop failing in the sixth, owing to drought) was 



Without manure, therefore, there was scarcely any produce 

 of turnips ; consequently, there was no exhaustion of the land 

 by removal of the crop, so that it was, practically speaking, 

 left fallow for the barley. With superphosphate alone only 

 small crops of turnips were grown, especially in the later 

 courses ; still, much more was removed from the land than 

 without manure ; and as nothing was supplied besides what 

 the superphosphate itself contained, the land was, so far as 



