Section VI. 
EARN FIELD ROOT-CROP SOILS. 
The experiments on the continuous growth of root crops in Barn 
field have been also full} 7 laid before you by Sir Henry Gilbert, 1 and 
I have only to add the results obtained by the chemical examination 
of a series of soil samples drawn from this field in the year 1870, after 
fourteen years' continuous growth of Swedish turnips under various 
conditions of fertilization. The system of the experiments, however, 
should be briefly described. 
The plats I have to refer to constitute four series or sets of 7 plats 
each. Plat 1 in each series has received annually a dressing of farm- 
yard manure, plat 2 in each series has also received farmyard manure 
but with superphosphate in addition. Plat 3 in each series has 
received no mineral or general manure. Plats 4, 5, and 6 in each 
series have received each year superphosphate with or without dress- 
ings of potassium salts and other alkaline salts during part of the 
period (see table) ; while plat 7 of each series has received throughout 
superphosphate with, during a portion of the period, ammonium sul- 
phate and alkaline salts. 
The plats in series 1 receive only the fertilizers aforesaid; but in 
series 2 all received in addition, for five years, a mixture of sawdust 
and nitric acid, and for the remaining nine years an annual dressing 
of sodium nitrate. 
In series 3 all the plats, in addition to the general manures, received 
ammonium salts. 
In series 4 all in earlier years received ammonium salts, supple- 
mented by sawdust, and in later years a heavy dressing of both 
ammonium salts and rape cake. While the plats of series 5 having 
in earlier years received sawdust, in later years received a heavy 
dressing of rape cake, but without ammonium salts. 
All the crops, both roots and leaves, were annually removed from 
the land. 
The following table, abbreviated from the Rothamsted Memoranda, 
gives the average annual produce of roots (neglect ing the leaves or 
tops) lor fifteen years, including the year after the soil samples were 
taken : 
1 U. S. Dept. Agr., Office of Experiment Stations Bui. No. 22. 
164 
