ON THE GROWTH OF LEGUMINOUS CROPS. 31 



lupulina, the Lotus corniculatus, and the Lathyrus pratensis ; the last 

 being replaced in the second year by Onobrychus sativa. The plants 

 which have maintained fair, but very varying character of growth, are 

 the Trifolium repens, Vicia sativa, Melilotus leucantha, and Medicago 

 sativa', and I propose to give some account of the growth of these 

 plants on this Clover-exhausted soil. 



That the surface-soil had become very poor in nitrogen is evident 

 from the fact, that the mean percentage of it in the sifted dry surface- 

 soil of 5 of the Clover plots was, in March 1881, only (H058, which 

 is considerably lower than was found in the same field many years 

 before, and lower than has been found in any of the fields at 

 Rothamsted excepting those where crops have been grown for many 

 years on the same land without nitrogenous manure. It is a point of 

 interest, however, that the percentage in the surface-soil is not so low 

 as in immediately adjoining land, which has been under alternate Wheat 

 and Fallow for nearly 30 years without manure. 



The real interest of the results depends on the amounts, and on the 

 difference in the amounts, of nitrogen, which the various plants have 

 assimilated over a given area, all growing side by side on the same 

 Red-clover-exhausted land, and with the same mineral manures, 

 without any nitrogen supply. 



Accordingly, the upper part of Table XV. (p. 32) shows the 

 estimated average amounts of nitrogen in the Gramineous crop, Wheat, 

 grown in alternation with Fallow, over 27 years to 1877 inclusive, and 

 in the Red-clover, (together with other crops when it failed) over 29 

 years, also to 1877 inclusive. Then, in the body of the Table are given, 

 the amounts of nitrogen in the Wheat alternated with Fallow, and in 

 the produce of five different Leguminous plants, during the subsequent 

 years, commencing with 1878, and ending with 1888. 



Thus, over the preliminary period, the Wheat gave an average 

 annual yield of nitrogen per acre of 17 Ibs., and the Clover gave, over 

 much the same period, an average of 32 Ibs. of nitrogen. 



Against these amounts, the various crops yielded, over the 

 subsequent years, averages as follows : The Fallow Wheat, over 11 

 years, 12 Ibs. ; the Red Clover (Trifolium pratense), over 8 years, 14 

 Ibs. ; the White Clover (Trifolium repens), over 11 years, 26 Ibs. ; the 

 Vetch (Vicia sativa), over 11 years, 77 Ibs.; the Bokhara Clover 

 (Melilotus leucantha), 62 Ibs. ; and the Lucerne (Medicago sativa), 

 over 11 years, 136 Ibs. 



Or, if we take the average amounts over the years of actual crop 

 only, the amounts were in the Wheat 22 Ibs., in the Red Clover 22 

 Ibs., in the White Clover 47 Ibs., in the Vetch 77 Ibs., in 1 the Bokhara 

 Clover 68 Ibs., and in the Lucerne the enormous amount of 166 Ibs., of 

 nitrogen per acre per annum. 



Again, if we take the total yields of nitrogen over the experimental 

 periods, we have, in the Wheat 133 Ibs., in the Red Clover 112 Ibs., 

 in the White Clover 283 Ibs., in the Vetch 846 Ibs., in the Bokhara 

 Clover 679 Ibs., and in the Lucerne 1,492 Ibs. ; that is, in the Lucerne 



