124 



THE ROTHAMSTED EXPERIMENTS. 



Table 40 

 explained. 



72 inches. In the case of several plots the results show, cal- 

 culated per acre, that the total amount of nitrogen as nitric 

 acid to the depth of eight times 9 inches, or 72 inches in all, 

 was 27.95 lb. in the unmanured plot, 20.72 lb. in that with 

 purely mineral manure, and 25.38 lb. in that of the plot 

 which had received both mineral and nitrogenous manure. 

 In the soil of the farmyard manure plot, on the other hand, 

 the amount was about twice as much — namely, 50.46 lb. 

 Excluding this last result, it may be said that the amounts of 

 nitrogen already existing as nitric acid, to the depth deter- 

 mined, were very small. 



These, then, were the conditions of the soil when the barley 

 and clover were sown in the spring of 1883. The clover grew 

 very luxuriantly from the first, so much so as to considerably 

 interfere with the growth of the barley. 



Table 40 shows the amounts of nitrogen per acre in the bar- 

 ley and clover in 1883, and in the clover in 1884 and 1885. 



TABLE 40. — Barley and Clover, grown after Beans, Geescroft 

 Field. Nitrogen removed per acre in the crops. 



It should be stated that the plots, the yield of nitrogen of 

 which is here given, do not exactly correspond with those for 

 which the yield of nitrogen in the beans was given ; some of 

 the barley and clover crops having been taken together where 

 no difference in the produce was observable. Thus, half the 

 plot represented as without manure had been unmanured 

 from the commencement — that is, for nearly 40 years, but the 

 other half received some nitrogen to 1878 inclusive, but had 

 since been entirely unmanured. Again, the results given in 

 the second line relate to the produce of a plot part of which 

 received purely mineral manure, but the other part ammo- 

 nium-salts or nitrate up to 1878, but none since. The results 

 given in the third line relate, however, to a plot which has 

 not received any nitrogenous manure from the commencement 

 of the experiments with the beans, but which was not brought 

 under experiment until 5 years later than the other plots. 



Thus, on a plot where a purely mineral manure containing 

 potash, but no nitrogen, had been applied for 27 years, to 



