On the Growth of Barley by different Manures, &,-c. 509 



more rapidly for a given amount of nitrogen supplied. The 

 action of the purely nitrogenous manures, is economised by ad- 

 mixture with a small quantity of superphosphate of lime, or other 

 appropriate mineral manure. Other things being equal, the 

 later the barley is sown, the less should be the proportion of 

 nitrogen in the manure, and the greater that of mineral constitu- 

 ents ; otherwise the crop is liable to be too luxuriant ; and with 

 a limited range of root in the soil, it will probably not find mi- 

 neral constituents rapidly enough in the later stages of growth, for 

 a favourable development and maturing of the seed. 



By the concurrent testimony of field experiments of very 

 various kinds, we have been led to the conclusion that full crops 

 of barley cannot be grown unless there be, by some means, avail- 

 able nitrogen provided Avithin the soil. It happens that in 

 practice it is frequently convenient to increase the produce of 

 the barley crop by the direct application of portable nitrogenous 

 manures. It is very desirable, therefore, both in a practical 

 and scientific point of view, to have some means of judging 

 of what is the probable proportion of the nitrogen so supplied in 

 manure, which will, on the average, or under given circum- 

 stances, be recovered in the immediate or successive increase of 

 crop obtained. We propose, therefore, to adduce such evidence 

 on these points as, by the aid of analysis, we are enabled to 

 provide. 



Before passing to this concluding division of the subject, how- 

 ever, it may be well to add a few words on the more marked 

 effects of direct mineral manures on the barley than on the wheat 

 crop. That such should be found to be the case is seen to be 

 quite consistent, on a consideration of the distinctive habits and 

 usual circumstances of growth in our rotations, of these two, 

 nevertheless much allied crops. 



The necessity of considering the various habits and conforma- 

 tion of the different crops of our rotations in relation to their 

 resources of growth, was prominently insisted upon in our early 

 papers in this Journal ten years ago. The important bearing of 

 stich considerations in modifying the conclusions, to which a 

 more purely chemical view of the offices and province in a system 

 of manuring of the various constituents would lead, is one of the 

 first lessons which the progress of field experiments teaches. 

 Indeed, in the early years of our own experiments, so desirable 

 did it seem, to verify and define the more obvious conclusions of 

 superficial observation on some of the points herein involved, 

 that the summer of 1846 was devoted mainly to the examination 

 of the comparative underground ranges of the various crops of 

 our rotations. The comparatively great depth and extent to 



