Rotation of Crops. 
591 
The Experiments on Rotation made at Rothamsted. 
The experiments have been conducted in Agdell Field. An 
area of 2^ acres is devoted to the purpose. The ordinary 
four-course rotation of — turnips, barley, clover (or beans), or 
fallow, and wheat, was adopted. The experiments were . com- 
menced in 1848, so that the eleventh course of four years each 
was completed with the harvest of 1891 ; and the wheat which 
has just been sown (October 1894) is the fourth crop of the 
twelfth course, and will complete the forty-eighth year of the 
experiments. 
The area of 2J acres was divided into three main divisions, 
which have, respectively, been under the following conditions 
as to manuring: — 
1. Without manure from the commencement. 
2. For the first nine courses, manured with superphosphate 
alone, applied only for the turnip crop commencing each course ; 
that is, once every four years. For the tenth, and each subse- 
quent course, salts of potash, soda, and magnesia, have been 
applied as well as superphosphate. 
3. A complex artificial manure, also applied every fourth 
year ; that is, for the turnips commencing each course. This 
manure comprises — superphosphate, salts of potash, soda, 
and magnesia, ammonium-salts, and rape-cake ; and it supplies 
about 140 lb. of nitrogen per acre for the four years’ course ; 
that is, an average of 35 lb. of nitrogen per acre per annum. 
The complex manure (3) was designed to be, in great measure, 
a substitute for farmyard manure ; and it was used instead of it, 
in order that the amount of the different constituents supplied 
might be more accurately known than would have been the 
case if farmyard manure had been employed. 
It should be further explained, that when the land is under 
turnips, the roots, with their leaves, are removed from one 
half of each of the three differently manured plots ; whilst, on 
the other half of each, the produce is consumed on the land by 
sheep ; or, if the weather be unsuitable for this, the roots are 
sliced, and both roots and leaves are spread on the land. Thus, 
each of the three main divisions is divided into two, making so 
far, six in all. 
Then again, after the first course of four years, in the third 
year of each course the leguminous crop was grown on only half 
of each of the three differently manured plots, and the other 
half was left fallow. Lastly, as clover cannot be relied upon on 
such land so often as once in four years, beans have frequently 
been grown instead. 
