The Lois Weedon Plan of Growing lllieat. 591 



common fallow. It is evident, therefore, that the less produce on 

 the trenched portion in tlie previous years, was in greater measure 

 due to the thin seeding- on the comparatively poor and raw turned- 

 up subsoil, than to any relative deficiency or want of available 

 condition of the food of the plant within the soil — provided only 

 that a sufTuiently healthy early development, and a sufficiently 

 wide distril)ution of the underground feeders of the crop, were 

 but obtained. 



Taking the produce of this unmanured portion thus explained, 

 as the standard by which to compare the effects of manures on 

 land in the same condition, we find that — 



'"'■ Mineral n)anures only'''' — gave an increase of not quite 2^ 

 bushels of total corn, and of only 2S4 lbs. of straw. 



" Ammoniacal salts oidi/ " — gave an increase of about 15 bushels 

 of total corn, and of 1695 lbs. of straw. 



" Minerals and ammoniacal salts " — gave an increase of rather 

 more than 20 bushels of corn, and of 2757 lbs. of straw. 



Those striking results can leave no doubt that the mineral 

 supplies in the soil in question were far in excess over the avail- 

 able and assimilable nitrogen. A comjiarison, too, of the middle 

 and the lowest divisions of the Table will show that, if we take into 

 consideration the very different condition of the land in the two 

 cases, the effects of these manures on the Lois Weedon or trenched 

 plots, were perfectly consistent in kind (though of course not equal 

 in degree) with those of the same manures in the adjoining field, 

 where they have bv^en applied, and tlie crop has been grown, for 

 many years in succession. 



Hundreds of other experiments, and the whole range of recorded 

 agricultural experience, conspire to show, that in ordinarily cropped 

 and cultivated soils, the available mineral supplies are generally 

 in excess relatively to the availaljle supply of nitrogen of the soil 

 and season, in the case of the wheat ciop : in fact that, excepting 

 in cases of very special and unusual exhaustion of the mineral or 

 soil-proper constituents, the direct supply of them by manure for 

 wheat does not increase the crop in any practicable and agricul- 

 tural degree, unless there be a liberal provision of available and 

 assimilable nitrofjen xmlhin the soil. Tiie results given above are 

 a remarkable illustration of this. Thus, when the mineral con- 

 stituents alone were added to this part fallow and onlv part crop- 

 exhausted land, tliey gave an increase of only 438 lbs. of total 

 produce; but when the same mineral constituents are added to 

 the same soil with ammoniacal salts, the increase over and above 

 that by ammoniacal salts alone is 1368 lbs., instead of only 438 lbs. 

 Here, too, is a suflicient incidental proof that the minerals were 

 added in a.i avaibihle form ; — indeed, that thevonlv required sufli- 

 cient available nitrogen within the soil to vield a larger crop than 



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