23 



the land for many years without manure. The treatment of 

 the land which resulted in this large return from previous 

 residues was however attended with an entire loss of its pre- 

 vious high condition, and reduced the soil to a low state of 

 fertility, a result which cannot generally be desirable. 



4. Rotation Experiments at Rothamsted. 



We turn now from the simple conditions attending the 

 continuous cultivation of grass, or of wheat, or barley, to the 

 much more complicated conditions which are met with in a 

 rotation. Fortunately for our purpose experimental rota- 

 tions have been carried on for many years, both at Kotham- 

 sted and at Woburn, under various systems of manuring. 



The rotation experiments at Kothamsted commenced in 

 1848, and have been carried on now for fifty years on one 

 uniform plan. 1 The field is divided into three equal parts, 

 on one of which no manure has been applied from the 

 commencement. On another, the swedes are grown with 

 mineral superphosphate only, to which in the last three 

 rotations salts supplying potash, soda, and magnesia have 

 been added. On a third division the swedes have always 

 received the superphosphate and the salts just named, and 

 in addition a liberal nitrogenous manuring, consisting of 

 2,000 Ibs. of powdered rape-cake, and 200 Ibs. of ammonium 

 salts, supplying in all about 141 Ibs. of nitrogen per acre. 

 No other crop besides the swedes has ever been manured. 



The rotation followed is the ordinary four-course, con- 

 sisting of swedes, barley, clover or beans, and wheat. On 

 one half of each division the turnips have been fed off by 

 sheep, or in later years sliced and ploughed in ; on the other 

 half, the whole of the turnip crop is carted off the field. In 

 the third year of each rotation one half of each division is 

 treated as a bare fallow, the other half being in clover or 

 beans. There are thus four plots in each division : 

 (1) Turnips fed, third year clover ; (2) turnips fed, third 

 year fallow ; (8) turnips carted, third year clover ; 

 (4) turnips carted, third year fallow. 



' Details of these experiments will be found in the Journ. of the Hoy. Agri. 

 Society, 1894, 585. 



