EXrEIlIMENTS ON CLOVEE-SOILS. 151 



** In separate portions of the three layers of soil, the proportions 

 of nitrogen and phosphoric acid contained in each layer of six 

 inches, were determined and found to be as follows : 



Sott dried at 212 deg. Fahr. 

 1st six "M six 3d six 

 inches, inches, inches. 



Percentage of phosphoric acid 249 .184 .172 



Nitrogen 1.62 .092 .064 



Equal to ammonia .198 .112 .078 



" In the upper six inches, as will be seen, the percentage of both 

 phosphoric acid and nitrogen, was larger than in the two follow- 

 ing layers, while the proportion of nitrogen in the six inches of sur- 

 face soil, was much larger than in the next six inches ; and in the 

 third section, containing no visible particles of root-fibres, only 

 very little nitrogen occurred. 



" In their natural state, the three layers of soil contained : 



1st six 2d six 3d six 

 inches, incites, inches. 



Moisture 17.16 18.24 16.62 



Phosphoric acid 198 .109 .143 



Nitrogen 134 .075 .053 



Equal to ammonia 162 .091 .064 



76s. 76,?. Ibs. 

 Weight of one foot square of soil 60 61 63 



" Calculated per acre, the absolute weight of one acre of this 

 land, six inches deep, weighs : 



Lbs. 



1st six inches 2,613,600 



2d six inches 2,657,160 



3d six inches 2,746^280 



" No great error, therefore, will be made, if we assume in the 

 subsequent calculations, that six inches of this soil weighs two and 

 one-half millions of pounds per acre. 



" An acre of land, according to the preceding determinations, 

 contains : 



1st six inches. 2d six inches, 3cZ six inches, 

 Lbs. Lbs. Lbs. 



Phosphoric acid 4,950 2,725 3,575 



Nitrogen 3,350 1,875 1,325 



Equalto ammonia _*j>? 2,275 1,600 



" The proportion of phosphoric acid in six inches of surface soil, ' 

 it will be seen, amounted to about two-tenths per cent ; a propor- 

 tion of the whole soil, so small that it may appear insufficient 

 for the production of a good corn-crop. However, when calcu- 

 lated to the acre, we find that six inches of surface soil in an acre of 

 land, actually contain over two tons of phosphoric acid. An aver- 

 age crop of wheat, assumed to be 25 bushels of grain, at 60 Ibs. per 



