The Lois IVeedon Plan of Growing Wheat. 617 



pheric influences generally, a greater power of absorption for 

 ammonia in relation to a given surface. The other of these Lois 

 Weedon soils, although absorbing a less amount of ammonia in 

 relation to a given weight having an equal surface exposed, un- 

 doubtedly offers, under equal circumstances in the field, a much 

 larger amount of surface for absorption than the soils at Rotham- 

 sted. Indeed, we can have little doubt, that to the difference 

 between the respective soils in the degree of the conjoint influ- 

 ences of mechanical division, and of power of absorption and 

 liberation (in part depending on it) of a sufficiency of available 

 nitrogen relatively to the available mineral constituents, must in 

 great measure be attributed the difference in the results obtained 

 at Lois Weedon and at Rothamsted, 



Further, in the results which have been recorded, whether in 

 the field or in the laboratory, we find additional confirmation of 

 the view : — 



" That the chemical effects o^ fallow, in increasing the growth of the cereal 

 grains, are not measurable by the amount of the additional mineral food of 

 plants liberated thereby ; these being, under ordinary cultivation, in excess of 

 the assimilable nitrogen existing in, or condensed within, the soil in the same 

 period of time. The amount of the latter, therefore — {i. e.) the available 

 nitroyen — is the measure of the increased produce of grain which will be 

 obtained." 



But the system adopted by the Rev. Mr, Smith, of growing 

 wheat year after year on alternate strips of the same land, and as 

 a general rule without any restoration, directly or indirectly, of 

 the mineral constituents removed in the crops, certainly docs not 

 come within the definition of " ordinary cultivation" as referred 

 to in the paragraph just quoted. AVhilst, therefore, a soil not 

 only rich in the absolute amount of the mineral constituents of 

 the crop, but one capable of sufficient mechanical division, and 

 susceptible to the liberating action of atmospheric influences, is 

 absolutely essential to the success of the plan, yet all experience, 

 practical and experimental, tends to show, that a large amount of 

 inherent mineral stores, and their easy liberation, or available 

 form for the use of the plant, will only suffice for the production 

 of full crops of wheat, provided there be at the same time a liberal 

 supply of available nitn^gen icithin the soil itself. 



