THE ROTHAMSTED SOIL 



The Rothamsted soil was described by Lawes in 1847, as follows : — 

 "The soil upon which my experiments were tried consists of rather a 

 heavy loam resting upon chalk, capable of producing good wheat when 

 well manured ; not sufficiently heavy for beans, but too heavy for good 

 turnips or barley. The average produce of wheat in the neighbourhood 

 is said to be less than 22 bushels per acre, wheat being grown once in 

 five years. The rent varies from 20s. to 26s. per acre, tithe free."" 



It is fairly uniform in the different fields, and consists essentially of a 

 heavy loam containing little coarse sand or grit, but a considerable amount 

 of fine sand and silt, and a large body of clay. In consequence, the soil 

 has to be worked with care, becoming very sticky and drying to im- 

 practicable clods if moved when wet. It " runs together "" if heavy rain 

 falls after a tilth has been established, and then dries with a hard, 

 unkindly surface, these difficulties being much exaggerated on the plots 

 which have been farmed for a long time without any supply of organic 

 matter in the manures. 



The most notable feature in the Rothamsted soil is the amount of 

 calcium carbonate in the surface layer ; analyses of the earliest samples 

 available (1856) show more than 5 per cent, in the surface soil of Broad- 

 balk field. The subsoil below the depth of 9 inches contains little or no 

 calcium carbonate, and this fact, together with the varying proportion in 

 the surface soil, indicate that the original soil was almost devoid of 

 calcium carbonate, and that the quantity now found in the surface soil 

 has all been applied artificially. 



AGDELL FIELD 



Crops grown in Rotation. 



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 continuously. It is divided into three main 

 plots, one of which (O) has received no manure, the second (M) mineral 

 manures only, 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 is 

 further subdivided : — Half the pldts carry clover or beans as the third 

 crop of the course, and half the plots are bare fallow. This shows the 

 effect of introducing the leguminous crop into the rotation, as compared 

 with the bare fallow. 



On this field the long-continued cropping without manure on O affects 

 the successive crops in the rotation very differently. The Swede crop is 

 least capable of growing in the impoverished soil, and is reduced to less 

 than a ton per acre ; the clover and barley crops are also small, but the 

 deep-rooted wheat crop is comparatively little affected, and yielded as 

 much as 24-2 bushels per acre in 1911, the sixty-fourth year without any 



