42 



The first of the leguminous crops, the yield of nitrogen in which 

 is recorded in Table I, is beans. Without manure the yield of nitrogen 

 was in the earlier years very much higher than with the cereals ; but 

 the decline was very great, and in the later years it was as low as 

 with the cereals. With mixed mineral manure, including potash, the 

 yield throughout was much higher, but the decline was, as without 

 manure, very great. We have not a sufficiently comparative series of 

 determinations of nitrogen in the soils of the bean plots, but such 

 results as are at command lead to the conclusion that there has been 

 a gradual decline in the percentage of nitrogen in the surface soils ; 

 but, considering the little tendency of the plant to throw out feeding 

 root in the superficial layers, it may be a question how far the reduc- 

 tion is due to exhaustion by the direct action of growth, or how far 

 to nitrification and passage of the nitrates downwards. 





Nitrogen in the Soils of the Experimental Glover Plots. 



The most important of the leguminous crops to which reference 

 has been made is red clover. In Table I is recorded the yield of 

 nitrogen over twenty-two years, 1849-70, in only six of which, how- 

 ever, was any crop obtained. The experiment has ' een continued, 

 with some modifications ; and in 1877, that is after twenty-nine years, 

 in nine of the last ten trials the plant had died ofp during the winter 

 and spring succeeding the sowing of the seed. Several small crops 

 have since been obtained, and in March, 1881, samples of soil were 

 taken from five places where no nitrogenous manure has been applied 

 from the commencement, and at each place to thi'ee depths of 9 inches 

 each. Exactly corresponding samples were also taken from an imme- 

 diately adjoining plot, which had been thirty years under alternate 

 wheat and fallow, without manure of any kind. The nitrogen was 

 determined in each of the five separate samples, and also in the mix- 

 ture of the five. Table XIII summarises the results. 



