374 



THE FARMER'S MAGAZINE. 



bausted for corn-giowtli, the following conclusions are 

 arrived at : 



" That exclusively mineral manures, and especially 

 those containing phosphoric acid, annually increased the 

 produce of barley ; even doing so in the first year of 

 their application on land in the condition described." 



" That with barley grown continuously on the same 

 land (as was the case with wheat), nitrogenous manures 

 had a much more striking effect than mineral manures." 



" That by the annual supply of nitrogenous manures 

 alone (nitrate of soda or ammoniacal salts), larger 

 successive crops both of corn and straw were obtained, 

 than by the annual use of 14 tons of farmyard manure, 

 with all its minerals, and certainly more nitrogen than 

 either the nitrate or ammoniacal salts employed by its 

 side." 



" That within certain limits, even on this compara- 

 tively exhausted soil (and it would probably be more 

 nearly so on soils in ordinary condition for the crop), 

 nitrate of soda, ammoniacal salts, and rape-cake, all 

 increase the produce of barley, approximately in pro- 

 portion to the amounts of nitrogen they respectively 

 supplied. Their comparative effects will, however, vary 

 somewhat according to season, the nitrate being gene- 

 rally more rapid in its action." 



" That to obtain a maximum amount of increase in 

 proportion to the nitrogen given in manure, the barley 

 crop will, on the average of seasons, bear a considerably 

 less acreage amount of it than is required by the wheat 

 crop under similar circumstances." 



" That the effect of a given amount of nitrogen, if 

 not excessive, will be considerably increased by the ad- 

 dition of certain mineral manures, especially those con- 

 taining phosphates. The action of the mineral manures 

 is very much increased under such circumstances ; that 

 is, their application gives very much more increase, 

 when there is present a liberal supply of available ni- 

 trogen within the soil, than when there is not." 



" In other words, a soil brought by previous cropping 

 into a condition to require manure of some kind before 

 it will grow a full crop of corn, when afterwards cropped 

 year after year with barley, only yields full crops 

 when a liberal amount of nitrogen is supplied to the 

 soil. Mineral manures, especially phosphates, con- 

 siderably increase the action of the nitrogen so sup. 

 plied ; but the effect of such mineral manures on the 

 increase of crop will be extremely limited, without 

 there be a liberal amount of available nitrogen within 

 the soil itself." 



The next set of experiments to be noticed, is that in 

 which barley was taken successively from the same land 

 in the seasons of 1853, '4, and '5, after ten successive 

 crops of turnips, which had been grown experimentally, 

 by different manures. 



On one plot, the last seven of the ten preceding crops 

 of turnips had been grown without any manure what- 

 ever ; and this unmanured produce, leaf and bulb toge- 

 ther, averaged little more than two tons per acre per 

 annum. The second plot had received for the last eight 

 of the ten crops of turnips liberal supplies of mineral 



coustitucnis, mostly in much larger quantities than they 

 were taken off in the root crops. Plot 3 had the same 

 mineral manures for the turnips as plot 2, and, in addi- 

 tion, during the six middle years of the ten, about 

 44 lbs. of nitrogen per acre per annum in the form of 

 ammoniacal salts. On the 4th plot there had been the 

 same mineral manures as on plots 2 and 3, and an aver- 

 age annual addition, during six of the years of turnips, 

 of about 95 lbs. of nitrogen per acre, in the form of 

 rape-cake. The turnips on the 5th plot had received 

 the same mineral manures as on plots 2, 3, and 4, and 

 in addition, during six of the years, both the ammoniacal 

 salts as on plot 3, and the rape-cake as on plot 4, which 

 together gave an average annual supply of about 140 lbs. 

 of nitrogen per acre. 



The mineral-manured plot gave much larger crops of 

 turnips than the unmanured one ; and the addition of 

 nitrogen, and other organic constituents of manure, as 

 on plots 3, 4, and 5, always afforded a further increment 

 of increase. But in neither of the three cases was the 

 nitrogen recovered in the increased produce of the 

 turnips equal to that which was supplied in the manure. 

 It might be expected therefore that where nitrogen was 

 supplied for the turnips — unless it were evaporated or 

 drained in some form from the soil, distributed too 

 widely throughout it, fixed in it in an unavailable con- 

 dition of combination, or in some way dissipated during 

 the growth of the plant — that there would be some re- 

 maining available for the three succeeding crops of 

 barley. The discussion of the results of the three years' 

 growth of barley, after the ten differently manured 

 turnip crops, is prefaced as follows : — 



" If the characteristic influence of a rotation of crops, 

 upon the increased growth of the cereals, be at all ma- 

 terially due to the elaboration in the soil, during the 

 growth of the other crops, of the necessary mineral sup- 

 plies for the white crop, it might surely be expected 

 that here, aften ten meagre, unmanured crops of turnips, 

 appropriating no amount of silicates, we should have, if 

 ever it were possible, a large produce of barley, de- 

 pending, with these rich stores of prepared mineral food 

 in the soil, upon atmospheric sources for its nitrogen? 

 If not after the many crops of unmanured turnips, surely 

 after those provided with a very large excess of other 

 mineral matters than silicates — the crop taking none of 

 the latter out— we should have enough elaborated and 

 conserved in the soil both of these and of all other 

 mineral constituents, to yield the fullest crop of barley 

 which it is possible to obtain by the conjoint influence 

 of a very rich mineral condition of soil, and the normal 

 season supplies of available nitrogen ?" 



But the result was that, comparing the produce of 

 barley after the unmanured turnips with the unmanured 

 produce during the same three years, in the field de- 

 voted to the continuous growth of the crop by different 

 manures, the turnip land gave an average annual pro- 

 duce of not quite 19 bushels of corn, and the continu-» 

 ous barley field nearly 32 bushels. The amount of 

 straw, too, was only about two-thirds as much after the 

 ten crops of turnips as in the field whence so much more 

 corn had been recently taken. In fact, a produce of 



