190 J. H. Gilbert— Points i, 



the amount not recovered, id the increase of crops for 100 sup- 

 plied in manure, to wheat, and to barley, respectively : the 

 result being in each case the average over a period of twenty 



meat 20 years, W2-im. 



Complex Mini Man! an 

 (Complex Min. Man. an 



I 41 lbs nitrogen as ammonia 



32-4 1 67-6 I 















Barky 20 years, 1852-1871. 



|Complex Min. Man. an 





48-1 | 51-9 | 





Speaking generally, it may be said that, notwithstanding 

 the great effects produced by the nitrogeuous manures, two- 

 thirds of the nitrogen supplied were unrecovered in the increase 

 of crop when the ammonia-salts were applied to wheat ; the ap- 

 plication being made in the autumn. When, however, nitrate 

 of soda was used, which is always applied in the spring, the 

 quantity lett unrecovered was not much more than half that 

 supplied. With barley also, the manuring for which takes 

 place in the spring, there is again nearly halt' the nitrogen sup- 

 plied in the manure recovered in the increase, and therefore 

 little more than half left unrecovered. 



It may be observed that, in the case of root-crops, when the 

 supply of nitrogen is not excessive, the proportion of the nitro- 

 gen of the manure recovered in the increase may be much greater 

 than in the case of the cereals; while in the case of the Legu- 

 minosse the effects of such direct application of soluble nitro- 

 genous manures to the surface soil is comparatively so small, 

 and so uncertain, that it would he useless to uive an estimate 

 of the amounts recovered and not recovered respectively. 



But what becomes of the one-half or two-thirds of the nitro- 

 gen supplied for the increased growth of the cereals, bat not 

 recovered in the increase of crop? Dr. Frankland and Dr. 

 Voelcker have made numerous analyses of the drainage water 

 from the ex; ..t.-wh'ieh have vielded the results 



TbT x ferred to ' and a suinmar .y of ^eir results is given in 



