ON THE GROWTH OF LEGUMINOUS CROPS. 



23 



yield in the 31st year (1884) was about 240 Ibs., and in the 32nd year 

 156 Ibs. of nitrogen. 



Further, the average over the third 10 years of the continuous 

 growth (122 Ibs.), was about as much as in a fair average crop grown 

 occasionally under the ordinary conditions of agriculture. 



There would seem, then, to be clearly indicated, a soil source of 

 failure on the arable-land, and a soil source of success on the garden- 

 soil. 



The results given in Table X. (below) will throw some further light 

 on this point. It shows the percentage of nitrogen in the first 9 inches 

 of depth of the garden-soil, in 1857 and in 1879, between which 

 periods the growth of 21 years had been removed. 



It also shows the estimated amounts of nitrogen per acre in the 

 surface soil at the two periods, and the reduction in the amount during 

 the 21 years. 



TABLE X. 

 RED CLOVER. 



Grown on Rich Garden Soil. 



Nitrogen, per cent, and per acre, in the fine soil, dried at 100 C. 

 (First 9 inches of depth) . 



It may be mentioned, that the percentage of nitrogen given for the 

 sample collected in October, 1857, is the mean of duplicate or more 

 determinations, made in 1857, in 1866, and again in 1880; and it is 

 almost identical with the results obtained at the latest of these dates. 



The first point to notice is, that the first 9 inches of depth of this 

 rich garden-soil contained more than half a per cent, of nitrogen ; that 

 is, nearly four times as much as the average of the Rothamsted arable 

 soils, and nearly five times as much as the exhausted arable Clover-land 

 soil where the crop failed. It is, of course, true, that the garden-soil 

 would be correspondingly rich in all other constituents ; but some 

 portions of the arable soil where the Clover failed, had received much 

 more of mineral constituents by manure than had been removed in the 

 crops. 



The result given for 1879 is the mean of determinations made on 

 three separate samples, for which the determinations agreed very well. 

 The results can leave no doubt that there had been a great reduction 

 in the stock of nitrogen in the surface-soil since 1857. The reduction 

 amounts to nearly 29 per cent, of the whole in the 21 years; and, 

 reckoned per acre, as shown in the bottom line of the Table, it corres- 

 ponded to a loss of 2,732 Ibs. during the 21 years; and, although, as 



