370 



THE i'AKMER'S MAGAZINE. 



organic matter), with, in three out of four cases, direct 

 mineral manures also, was 8,1501b8." 



" In the contrasts and coincidences afiforded by the 

 results in these two fields, we have the clearest evidence 

 that it was in available nitrogen for the barley crop 

 that the previously mineral-manured turnip soil had be- 

 come deficient, as compared with the unmanured land 

 in the field of continuous barley experiments. It is 

 evident, moreover, that on the mineral-manured turnip 

 plots there was an abundant provision of the requisite 

 mineral constituents for an exceedingly full crop, within 

 the reach of the barley plant, provided only available 

 nitrogen were also within the reach of its roots. Lastly, 

 with the widely differing condition of the land in the 

 two fields without further nitrogenous manure, and the 

 approximation to equal amounts of produce when with 

 comparable other conditions, both are supplied with a 

 full dressing of such manure, again we learn how 

 marked is the influence of season on the productive 

 effects of our most active manures." 



With the further light upon the " conditioti" of soil 

 required by the barley crop, which the examination of 

 the produce obtained after ten years of turnips, and its 

 comparison with that in the other field, affords, the re- 

 sults obtained in still another field, under circum- 

 stances differing widely from either of the other two, 

 are next to be considered. 



In 1848, three portions, of nearly an acre each, were 

 set apart for separate experiments on the chemical 

 statistics of rotations of crops. For all three of these 

 portions of land, the rotation chosen was — turnips, bar- 

 ley, clover, wheat. As was to be expected, however, 

 the clover, coming round after a lapse of only four years, 

 failed ; hence, in the second and third courses, half of 

 each plot was sown with beans, and the other half 

 fallowed, instead of the clover. None of the crops were 

 manured, excepting the turnips. 



The plot of rotation No. 1 remained entirely un- 

 manured — even the turnips— course after course. 



The turnips of rotation No. 2 were manured, each 

 time they came round, with superphosphate of lime 

 alone. 



The turnips of the third plot (rotation No. 3) were 

 manured, each course, with superphosphate of lime, the 

 sulphates of potash, soda, and magnesia, 2,0001bs. rape- 

 cake, and lOOlbs. each sulphate and muriate of ammonia 

 per acre. 



There were, therefore, three parallel rotations with 

 the same crops ; one of these had no manure whatever, 

 course after course ; the second had superphosphate of 

 lime alone, once in four years ; and the third, after the 

 same interval, received a mixed manure, supplying 

 liberally to the soil phosphates and other mineral con- 

 stituents, and both nitrogen and carbonaceous organic 

 substance. 



In each of the three four-course rotations, barley has 

 been taken three times— namely, i;i 1849, in 1853, and 

 in 1857; and, as from half of each turnip. plot the 

 entire produce, leaf and bulb, was carted-off, and on the 



other half the roots were eaten by sheep, and the leaves 

 distributed over the land, the produce of the barley on 

 each turnip-plot was so subdivided, as to show the com- 

 parative effects of the drawing-off and folding. The 

 turnips on the continuously unmanured plot averaged 

 only from 4 to i-^ ^oiis per acre, per course, leaf and 

 bulb together ; the superphosphated turnips from 13 to 

 14 tons ; and those by the full mixed manure, over 20 

 tons. 



The result was, that the produce of barley obtained in 

 rotation, even when the turnips were both unmanured 

 and carted-off, was considerably greater than when, as 

 in the field first described, the crop was grown annually 

 in succession on the same land, without manure. This 

 was even more strikingly the case in the third un- 

 manured rotation- course than previously. And it will 

 be remembered that the barley grown continuously in 

 succession was, in its turn, considerably more than that 

 after the series of unmanured turnip-crops as in the 

 second field considered. Consistently with this last 

 point, the produce of barley in rotation was considerably 

 less after those carted-off turnips which were grown by 

 superphosphate of lime, than after those grown without 

 any manure whatever. This is explained by the fact 

 that rnuch larger crops of turnips were taken from the 

 superphosphated than from the unmanured land. On 

 the other hand, as was to be expected, the fed super - 

 pJiosphated turnips gave larger succeeding crops of 

 barley than the fed unmanured ones. 



On the unmanured rotation-land, the folding of the 

 meagre crops of turnips did not increase the produce of 

 barley. On both the superphosphated and the mixed- 

 manured rotation-plots, the folding of the turnips did 

 much increase the produce of barley. The difference 

 in the amount of barley after the folding, compared with 

 that after the carting off of the turnips, was greatest ou 

 the superphosphated plot; in which case the exhaustion 

 of the land by the removal of the turnips was the 

 greatest, and the manuring from the folding was not 

 too high. In fact, on the highly manured rotation-plot, 

 the land after the removal of the turnips was still left 

 in good condition, and after the folding in too high a 

 one for the barley to stand the vici^situdes of season — 

 under which it was the more liable to injury when 

 manured beyond a somewhat limited degree. 



It will now be interesting, for a moment, to review as 

 a whole, the various field experiments on the growth of 

 barley. 



" It has been found, that the amount of produce 

 when grown after a succession of removed unmanured, 

 or even highly mineral-manured turnip crops, was far 

 below a moderate agricultural yield. It was seen that 

 by the simple addition of nitrogenous manure to 

 land in this condition, enormous crops were raised. 

 When barley was grown without manure year after year, 

 on land in a less artificially exhausted condition than 

 that where ten successive turnip crops had been grown, 

 the produce was considerably greater than after the 

 succession of turnip crops. On this land mineral 

 manures somewhat increased tde produce. But, as on 

 the turnip eihausted land, nitrogenous manures did so 



