i2o Conservation of the Fertility of the Soil, [may, 



The following table shows the percentage of nitrogen in the 

 surface soil (9 inches) at the respective dates, together with 

 the average crops on each plot over the period 1 852-1903. 



Nitrogen per cent, in Soil of Agdell Field, Rothamsted. 

 The plots all receive mineral manures, but no nitrogen. 





Fallow. 



Clover. 



Roots carted off. 



\ . 13/14. 



Roots returned. 

 9/10. 



Roots carted off. 



' T5/1.6. 



Roots returned. 

 11/12. 



1867 



1874 



1883 



1909 "... .. ... 



OI224 

 0*1147 

 o - i 161 

 0-1159 



0*1240 

 0*1238 

 CI228 



0*1195 



0*1327 

 0*1241 

 0*I329 

 OT347 



0*1380 

 0*1321 

 0-1383 

 0*1498 



1852— 1903 











Wheat average 



31*2 bushels 



32*2 



32*2 



35'i 



Clover ,, 







41 *o cwt. 



477 



Swedes 



151 -o cvvt. 



268 



160 



187 



Barley . , 



22- 1 bushels 



28*7 



24-5 



34-5 



The changes indicated in the amount of nitrogen in the 

 soil are not large, being, indeed, very close to the experi- 

 mental error; but, reviewing the numbers altogether, it may 

 safely be concluded that the first plot, 13/14, from which 

 the roots are carted and where no clover is grown, is declining 

 in fertility. The two plots 9/10 and 15/16 are practically 

 stationary; if anything, 9/10 without clover may be losing 

 ground, w T hereas 15/16 with clover, but from which the roots 

 are carted, may be gaining ground; while the plot 11/12, on 

 which both the roots are returned and clover is grown, is 

 still more probably gaining a little fertility. This last plot has 

 yielded on the average over 52 years 35 bushels of wheat, 

 34 bushels of barley, over 9 tons of swedes, and nearly 

 2 \ tons of clover hay per acre, which is nearly equal to, if 

 anything higher than, the average production of the whole 

 of Great Britain during that period. Such a yield, which, 

 though equal to the average, may be taken as lower than 

 a good farmer would expect from that class of land, has been 

 obtained without bringing in any external source of nitrogen, 

 without even returning to the land all that would come hack 

 under ordinary conditions of farming. In practice it would 

 not always be possible to feed off the root crop on the land, 



