43C 



MK. J. B. LA.WBS, DE, GILBERT, A^'D Dii. 1'LGJI US 



experiment; that is to say, it had heen brought to such a condition by previous croj>- 

 piug, that, in the ordinary course of practice, it would be deemed necessary to supply 

 manure to it before growing another corn-crop. It may be further remarked that in 

 the case of the wheat there is as yet little, but in that of the barley more obvious 

 indication of progressive decline in the annual yield. 



The meadow-land yielded nearly -10 lbs. of Nitrogen per acre, per annum, or a'r 

 one-half more than the exclusively Graminaceous crops, wheat and barley. The hetero- 

 geneous produce, meadow-hay, contained, however, a good deal of Trifolium, and other 

 Leguminous plants, intermixed with the Grasses. To this fact is to be attributed, at 

 least in great part, its comparatively high amount of Nitrogen. It should be observed, 

 too, that the average is as yet taken over only four years. 



The Leguminous crop (beans) has given, over a period of twelve years, an average of 

 nearly 48 lbs. of Nitrogen per acre, per annum. The yield of Nitrogen in this Lejumi- 

 nous crop was, therefore, nearly twice as great as in the Graminaceous corn-crops. The 

 bean and allied crops are, however, very subject to disease, especially when grown too 

 frequently on the same land. It is, at least in part, owing to this circumstance, that 

 the average annual yield over the twelve years was so much less than would be the 

 yield of the crop when grown in suitable alternation with others in a season of average 

 adaptation for its healthy development. In fact, so great was the deterioration in the 

 character and amount of produce in the experiments in question, due to the continuous 

 cropping, that whilst the average annual yield of Nitrogen over the first six of the 

 twelve years was 70 lbs., that over the concluding six years was only 2G lbs. Nor did 

 the addition of nitrogenous manure in the form of ammonia-salts, together with liberal 

 mineral manuring, obviate this deterioration in any material degree more than did 

 mineral manures alone. 



In further illustration of the larger amount of Nitrogen obtained over a given area of 

 land in Leguminous crops than in Graminaceous ones, some remarkable results with 

 clover may be cited. Eed clover was grown in three out of four consecutive years, the 

 intermediate crop being wheat — all without manure. The following amounts of 

 Nitrogen were obtained per acre : — 



Table II. 



All further attempts to grow clover year after year, on this land, have, however, 

 failed. Neither ammonia-salts, nor organic matter rich in carbon as well as other 

 constituents, nor mineral manures, nor a mixture of all has availed to restore the 



