EXPERIMENTAL STATIONS — BARLEY CROP, 1887. 223 



diiring the growing season, that a large patch of the plot lost 

 its braird, probably on account of injury done to the soil during 

 the removal of the potato crop. It was difficult to make an 

 allowance for the injury, and perhaps it would have been better 

 if the plot had been omitted from the report. 



Taken as a whole, the crop grown on the unmanured parts of 

 the station is chiefly of use in showing that the effects of light 

 manures, applied several years before, are still visible after the 

 removal of an oat crop and a potato crop ; but as the residues 

 picked up by the potato crop were greater in amount and dif- 

 ferent in kind from those removed by the barley crop, only a 

 very partial view of the nature and amount of unexhausted 

 fertility can be had by confining our attention to the results of 

 the barley crop we are now considering. It is evident from 

 these experiments that, in order to get a fair measure of unex- 

 hausted fertility, a variety of crops, having different manurial 

 wants, must be grown on the land, and that, to give satisfactory 

 information on the subject, a whole rotation of crops would 

 require to be reaped after the manuring had been discontinued. 

 On referring to the report of the potato crop grown without 

 manures the former year, it is found that many of the plots 

 which have shown larger residues for the barley are precisely 

 those which had on the previous year grown a very poor potato 

 crop, so that when the residues picked up by the potato crop 

 and the barley crop are added together, the total amount of 

 residual fertility given up by the plots that received a full 

 manuring are almost exactly on a level. 



We may now pass from this subject with the remark that the 

 object of leaving half of each plot unmanured on this station 

 was not only to gain some information regarding unexhausted 

 manures, but also, and more particularly, that the unmanured 

 half of each plot might serve as a standard by which to measure 

 the effects of the manures applied to the other half. 



Manured Section. 



It will be seen at a glance that the dotted curve on chart VI., 

 representing the crop grown with the use of manures, presents a 

 marked contrast to the one we have just been examining. 



The deep depressions in the curve at 17, 22, 27, 7, and 10 

 indicate plots which have received no nitrogenous manures, and 

 they show plainly that the one constituent that chiefly affected 

 the growth of barley at Harelaw was nitrogen. On no former 

 occasion has the want of nitrogen had so powerful an effect in 

 diminishing the crop. Most of the other plots had nitrate of 

 soda applied to them as the nitrogenous constitutent of their 

 manure, and this circumstance brings to the front the import- 

 ance of soluble nitrogenous manures for the growth of cereals, 



