1st six 2d six 3d six inches. inches. inches. Moisture 17.16 18.24 16.62 Phosphoric acid .198 .109 .143 Nitrogen .134 .075 .053 Equal to ammonia .162 .091 .064 Lbs. Lbs. Lbs. 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 2d six 3d six inches, inches, inches, Lbs. Lbs. Lbs. Phosphoric acid 4,950 2,725 3,575 Nitrogen 3,350 1,875 1,325 Equal to ammonia 4,050 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 proportion of the whole soil, so small that it may appear insufficient for the production of a good corn-crop. However, when calculated 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 average crop of wheat, assumed to be 25 bushels of grain, at 60 lbs. per bushel, and 3,000 lbs. of straw, removes from the land on which it is grown, 20 lbs. of phosphoric acid. The clover-soil analyzed by me, consequently contains an amount of phosphoric acid in a depth of only six inches, which is equal to that present in 247½ average crops of wheat; or supposing that, by good cultivation and in favorable seasons, the average yield of wheat could be doubled, and 50 bushels of grain, at 60 lbs. a bushel, and 6,000 lbs. of straw could be raised, 124 of such heavy wheat-crops would contain no more phosphoric acid than actually occurred in six inches of this clover-soil per acre.