436 MR. J. B. LAWES, DR. GILBERT, AND DR. PUGH ON 
experiment; that is to say, it had been brought to such a condition by previous crop- 
ping, 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 40 lbs. of Nitrogen per acre, per annum, or above 
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 Legumi- 
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 26 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. Red 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. 
Season. : Crop. Nitrogen per acre. 
Ibs. 
Ist Year, 1849 ...... ; Clover. 206:8 
(2nd Year, 1850 ... Wheat. 45°2) 
3rd Year, 1851...... Clover. 29°3 
4th Year, 1852...... Clover. 111-9 
Average of the three years Clover ,........ 116-0 
All farther 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 
