EXPERIMENTS AT ROTH AM ST ED 83 



experiment to apply lime to the land. A preliminary trial with 

 chalk at one end of some of the plots was made in 1881. In 

 November, 1883, lime was applied to one half of all the plots ; 

 and in November 1887, lime was applied to the remaining 

 halves, except in the case of plot 5, one half of which remained 

 without lime till 1896. The weights of hay given in the 

 following table are the mean produce of both halves of each 

 plot. 



During the first 19 years of the experiment only a single 

 cutting of hay was taken ; the autumn growth was either fed 

 off by sheep receiving no other food, or was occasionally cut 

 and spread on the land. From 1877 to the present time the 

 second growth has generally been made into hay ; when weather 

 did not permit of this it has been cut and weighed, and the dry 

 matter determined in the laboratory, from which its equivalent 

 in hay has been calculated. In Table XXV (p. 84) the produce 

 given for the first 20 years is the weight of the first or main 

 crop of hay ; for the second 20 years the weight of hay in both 

 first and second crops is given. 



The produce of the unmanured plot, and of that receiving 

 superphosphate only, is seen to have been very moderate, 

 amounting in the first twenty years to an average of 21-22 cwts. 

 of hay per acre, and in the second twenty years, in which the 

 autumn growth is included, to 25-26 cwts. per acre. 



\Yhen salts of potash, soda, and magnesia are added to the 

 superphosphate, there is a large rise in the produce, the average 

 for the first twenty years being 35 cwts., and for the second 

 twenty years 44 cwts. This remarkable crop, obtained without 

 any nitrogenous manure, is due to the extraordinary develop- 

 ment of leguminous herbage produced by the mixture of alkalies 

 and superphosphate. Agriculturists are now familiar with the 

 fact that leguminous plants obtain a great part of the nitrogen 

 which they require from the atmosphere. Nor do they obtain 

 this nitrogen for themselves alone, for the annual decay of the 

 leguminous plants enriches the soil with nitrogenous matter 

 which can be made use of by the grasses, and by other plants 

 which are themselves unable to feed on atmospheric nitrogen. 

 The independence of a clover crop of nitrogenous manure, and 



