>fANi r.E van n.vni.EY. 251 



gen in llio soil In otliiT wonls, the iiirnii)s IcaVi; ItKi aviiihiblo 

 nitro^oii in the soil liian j^rain crops. 



Aftrr aiiuilini; to llie fat-Is given in liic foregoing table, Messrs. 

 Lawrs ami Gilbert say : 



" There is eviilenee of another kind that may be cited as show- 

 ing that it was of available nitrogen that the turnii)s hail rendered 

 the soil so delicicnt for the aftergrowth of barley. It may be as 

 sumed that, on the average, between 2') and ^0 lbs. of nitrogen 

 would be annually removed from the Rothainsted soil by wheat 

 or barley grown year after year witlioul nitrogenous manure. But 

 it is estimated that fron> the niineral-nianured turnip-plots there 

 were, over the 10 years, more than 50 lbs. <»f nitrogen per acre per 

 annum removed. As, however, on some of the plots, small quan- 

 tities of ammonia-salts or rape-cake were ai)plie.l in the first two 

 years of the ten of turnips, it is, perhaps, more to the purjxise to 

 tiike the average orer l lie last 8 yeai-s of turnips only ; and this 

 would show about 45 lbs. of nitrogen removed per acre per annum. 

 An immaterial proportion of this migiit be due to the small 

 amounts of nitrogenous manures applied in the first two years. 

 Still, it may be assumed tLat about li time as much nitrogen was 

 removed from the land for 8, if not for 10 years, in succession, as 

 would have been taken in an equal number of crops of wheat or 

 barley grown without nitrogenous manure. No wonder, then, 

 that considerably less barley has been grown in 3 years after a 

 series of mineral-manured turnip-crops, tlian was obtained in an- 

 other field after a les? number of corn-crops. 



"The residts obtained in Barn-field afford a striking illustration 

 of the dependence of the turnip-plant on a supply of available ni- 

 trogen within the soil, and of its comparatively great power of 

 exhausting it. They are also perfectly consistent with those in 

 Hoos-field. in showing that mineral manures will not yield fair 

 crops of barley, unless there be, within the soil, a liberal supply of 

 available nitrogen. The p'sults obtained under such very ditTerent 

 conditions in the two fields are, in fact, .strikingly mutually con- 

 firmatory." 



