Seotioh VII. 
AGDELL FIELD EXPERIMENTAL ROTATION SOILS. 
Ii will be appropriate next to consider the results of the analyses 
which have been made of soils collected from the Agdell rotation field; 
but first the nature of the experiments must be briefly recalled to you. 
The experiments began in 1848. One-third of the land has been 
continuously anmanured; one-third, during the time with which we 
are here concerned, was manured with superphosphate once every four 
years (namely, for the turnip crop commencing each rotation), while 
one-third has been (also once in each rotation, namely, for the turnip 
crop) treated with a complex mixture of mineral and nitrogenous fer- 
tilizers, including phosphates, potassium, sodium, and magnesium 
sails, ammonium salts, and rape cake — hereafter referred to as " mixed 
manure." On One-half of each of the three differently manured plats 
the turnip crop, both roots and leaves, has been annually carted or 
removed from the field, while on the other half the turnips have been 
either consumed on the plats by sheep or spread and plowed in. The 
rotation followed has been turnips, barley, clover (or beans), and 
wheat ; but on one-half of each rotation plat only has clover or beans 
been sown, the other halt* forming a bare fallow. 
We have therefore really, for each system of manuring, four rota- 
t ions, namely, as follows : 
Turnips (carted), barley, clover, wheat. 
Turnips (fed on the land) barley, clover, wheat. 
Turnips (carted), barley, fallow, wheat. 
Turnips (fed on the land), barley, fallow, wheat. 
It is obviously a matter of interest to consider how far, over. a num- 
ber of years, the carting or consumption of the turnips on the one 
hand or the growth of leguminous vegetation on the other, as com- 
pared with fallow, affected the nitrogen contents of the soil. 
The samples of the soil were collected in 18(37, at the end of twenty 
years, or five complete rotations.; again in 1874, after twenty-seven 
years, or not quite seven rotations; and again in 1883 and 1884, after 
thirty-six years, or nine complete rotations. 
Two tables are here given, showing the nitrogen contents found at 
these various periods in the surface soils of the various plats. One 
table gives the quantities of nitrogen stated as, percentages in the sur- 
face soil, the other in pounds per acre for the first 9 inches. 
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