522 CHEMISTRY. 



THE ATJNf At YIELD OP NITE06EN PEB ACRE IN BIFFEEENT CEO?S. 



Those elaborate agricultural experimenters, scientific and practical, J. B- 

 lawes, F.R.S., and J. H. Gilbert, Ph. D., F.C.S., read, at the meeting of the British 

 Association for the Advancement of Science, recently held in Leeds, an interesting 

 and somewhat original paper on the above subject, of which the following is a 

 tery brief abstract. The extensive, accurate and costly investigations "which the 

 •Writers have been in the habit of pursuing for a number of years, on Mr. Lawes' 

 estate at Rothamsted, in Hertfordshire, give great weight to. the conclusions at 

 \vhich they may arrive, in reference to scientific and practical agriculture. 



The assimilation of free nitrogen by plants, the authors had determined by 

 carefully conducted experiments made in the field. The amount of nitrogen 

 yielded per acre per annum, in different crops, — even when unmanured, — was con- 

 siderably beyond that annually coming down in the forms of ammonia and nitric 

 acid, iu the yet measured and analysed aqueous deposits from the atmosphere. 

 The annual produce of nitrogen per acre had been determined from various crops, 

 grown consecutively for several years on the same land, — such as, wheat, fourteen 

 years ; barley, six years ; meadow hay, three years ; clover, three years out of 

 four ; beans, eleven years ; and turnips, eight years. In most of these instances 

 the yield of nitrogen had been estimated, both for the crop grown without manure 

 of any kind, and for that with purely mineral manure, having no artificial supply 

 of nitrogen. 



Beans and clover were found to yield several times as much nitrogen per acre 

 as wheat or barley, yet their crops were an excellent preparation for wheat. A 

 jear's falloio, and adding nitrogenous manure, had each been found similarly to 

 increase the produce of the cereal crops. Other results obtained illustrated the 

 fact, that four years of wheat, alternating vnth fallow, gave as much nitrogen in 

 eight years as eight crops of wheat grown consecutively. Again, four crops of 

 wheat, grown in alternation with beans, yielded nearly the same amount of nitro- 

 gen per acre as the four crops grown in alternation with fallow ; consequently, 

 also, much about the same as the eight crops of wheat grown consecutively. la 

 the case of the alternation with beans, therefore, the whole of the nitrogen 

 obtained in the beans themselves was over and above that which was obtained 

 during the same series of years in wheat alone, whether it was grown consecutively 

 or in alternation with fallow. , 



Interesting questions arose, therefore, as to the varying sources or powers of 

 accumulation of nitrogen in crops so dissimilar. Leguminous crops, yielding a 

 large amount of nitrogen, were found in practice to be not materially benefitted 

 by the application of nitrogenous manures ; while the cereals affording a compara- 

 tively small quantity of nitrogen, are found much benefitted by such manures. It 

 was found that over a series of years only about four-tenths of the nitrogen 

 annually supplied in manure for wheat or barley was recovered in the immediate 

 crop. It was an interesting and, as yet, in part unsolved question, what became 

 of this unrecovered amount of nitrogen. Has it been drained away and lost? or 

 did a poi'tion remain in a fixed and unavailable state of combination in the 

 soil ? Further elucidation is necessary before such enquiries, connected with 

 agricultural theory and practice, can be satisfactorily explained. Chemistry has 

 yet much light to throw upon these anomalous and difficult matters. G. B. 



