Nitrogen of the Soil. 153 



nitrogen) ? Analyses of the soils reveal a considerably lower 

 percentage of nitrogen in the first 9in. of depth of the mineral 

 manured plot 7 than in that of the unmanured plot 3, the 

 difference being more than sufficient to account for the 

 increased yield of nitrogen over the twenty years in both the 

 gramineous and the leguminous herbage of plot 7. It would, 

 in fact, appear that, under the influence of the mixed mineral 

 manure alone, both the powers of collection, assimilation, and 

 transformation of the plants themselves, have been consider- 

 ably augmented, and the accumulated stores of nitrogen in 

 the soil have been rendered more available. 



With regard to mineral matter, plot 7, liberally supplied 

 with mineral manures, yielded in its herbage over the first 

 period nearly one and two-thirds as much, over the second 

 period more than twice as much, and over the entire period 

 nearly twice as much, as the unmanured plot 3. Potash and 

 phosphoric acid rank first ; of the former nearly three and a 

 half times as much, and of the latter nearly three times as 

 much, being taken up on the mineral-manured plot as on the 

 unmanured plot. 



The general result is that a mixed mineral manure alone 

 has markedly influenced the description of plants developed, 

 and has greatly favoured the tendency to form stem and seed 

 that is, to mature ; it has also much increased the amount 

 of total produce grown, and of nitrogen as well as mineral 

 matter taken up. The evidence, so far, points to the potash 

 of the manure as mainly conducive to these effects, the 

 phosphoric acid probably coming second in order of import- 

 ance. 



5. Superphosphate of Lime Alone : Plot 4 I. This plot 

 has received phosphate alone every year from 1859. In each 

 of the three preceding years (1856-7-8) it received sawdust 

 (20001b. per acre per annum), with the object of testing 

 Leibig's assertion that it produced great effects by virtue of 

 the solvent action exerted by the carbonic acid, yielded in 

 decomposition, upon the mineral constituents of the soil. 



