On the Growth of Barley by different Manures, S^'c. 531 



deciding whether or not the crop grown by nitrogenous manure, 

 has assimilated the same amount of nitrogen from other sources 

 as that grown without it. We cannot say, therefore, whether the 

 soil has to render an account of more or less of nitrogen than that 

 indicated by the column of the amounts unrecovered in the 

 increase of crop. The proportion unrecovered in the immediate 

 increase is, however, obviously very large. It may be supposed 

 that this at first unrecovered amount, is still available to after-crops? 

 We may as alternatives assume — that a portion is locked up in the 

 soil in a practically unavailable form ? — that it passes into states 

 of combination in which it can be drained away, or evaporated, 

 from the soil ? — or lastly, that in some form or other it is got rid 

 of by the functional processes of the growing crop ? The actual 

 or relative amounts of these several influences, science is not yet 

 able to determine. 



It is obvious that, at any rate some of the apparent loss to 

 immediate increase, of the supplied nitrogen, will be due to the 

 unequal distribution of the manure in relation to the underground 

 feeders of the plant. If this were all, however, the unrecovered 

 nitrogen in a fii'st crop, should be sooner or later available to those 

 which follow. But one thing is certain ; that, even taking together 

 the increase in several immediately succeeding after years, the 

 proportion then recovered of the previously unrecovered nitrogen, 

 is very much less than the proportion of the whole supplied, 

 which is recovered in the year or years of its application. This 

 is even the case when the provision of the necessary mineral con- 

 stituents is very liberal. Indeed, a much less amount of nitrogen 

 newly supplied in the form of salts of ammonia or nitrate of 

 soda alone, will give a greater increase of produce than the 

 larger amount of supposed residual nitrogen, with direct mineral 

 manures in addition. It cannot well be supposed, therefore, 

 that the amount of the supplied nitrogen unrecovered, is simply 

 due to its greater distribution, though still remaining, so far as 

 state of combination is concerned, available. 



As a fact in practical agriculture, it must be concluded, that the 

 nitrogen supplied in manure for full crops of grain, is not reco- 

 vered in the increase within any moderate period of time. We 

 hope on an early occasion to add to the statistical results in this 

 and in former Papers on other crops, those relating to the propor- 

 tion of nitrogen recovered in increase, to that supplied in manure, 

 for yrass. But even with all the evidence which the facts of the 

 field will be able to provide, the exact explanation of the loss 

 which is experienced by practice will still remain to be given by 

 science. 



END OF VOL. XVIII. 



