12 



THE KOTHAMSTED EXPERIMENTS. 



III. — Experiments on the Growth of Various Leguminous Crops for 

 many years in succession on the same land ; also on the 

 Question of the Fixation of Free Nitrogen. 



Introduction . . . . . . . .100 



Yield of nitrogen per acre in different crops . . . .101 



Effects of nitrogenous manures in increasing the produce of various crops 106 



Effects of nitrogenous manures on leguminous crops . . .111 



Growth of red clover, year after year, on rich garden soil . . 118 



Red clover grown after beans . . . . . 123 



Various leguminous plants grown after red clover . . .126 



Evidence as to Fixation of Free Nitrogen. 



Earlier experiments which did not show fixation of free nitrogen . 140 



Recent experiments which do show fixation of free nitrogen . . 144 



How is the fixation of nitrogen to be explained ? . . .153 



Of what importance to agriculture is the newly-recognised source of 



nitrogen to leguminous crops ? . . . . .161 



IV. — Experiments on the Growth of Wheat for more than fifty 



YEARS IN SUCCESSION ON THE SAME LAND ; BROADBALK FlELD, 



Rothamsted. 



Introduction ... 



The field experiments on wheat 

 Without manure every year 

 Farmyard manure every year 

 Various artificial manures 



Summary and general conclusions 



166 

 166 

 167 

 170 

 172 

 188 



V. — Rotation of Crops. 



Introduction and historical sketch . . . . .195 



The experiments on rotation made at Rothamsted . . . .199 



The Swedish turnip crops ..... 200 



The barley crops . . . . . . . 205 



The leguminous crops (or fallow) ..... 208 



The wheat crops ....... 212 



The amounts of produce grown in rotation, and in the various crops 



grown continuously . . . . . .218 



The amounts of dry matter produced in the rotation, and in the 



continuous crops . . . . . .218 



The amounts of nitrogen in the rotation, and in the continuous crops 225 

 The amounts of total mineral matter (ash) in the rotation, and in 



the continuous crops . . . . . .231 



The amounts of phosphoric acid in the rotation, and in the con- 

 tinuous crops . . . . . . .231 



The amounts of potash in the rotation, and in the continuous crops 237 

 The amounts of lime in the rotation, and in the continuous 



leguminous crops ...... 244 



Summary and general conclusions ..... 249 



VI. 



-The Feeding of Animals, for the Production of Meat, Milk, 

 and Manure, and for the Exercise of Force. 



Introduction and history 



The Rothamsted feeding experiments 



255 

 261 



