70 [Senate 



In this analysis, 1,000 pounds of the grain, or straw, was used ; the 

 same quantity of dried hay, clover, &c. ; while of the roots, the cal- 

 culation is for 10,000 pounds of each kind, as they are taken from 

 the field. If we make this allowance, or take nine-tenths from the 

 amount stated in the analysis of the roots, we shall perceive that 

 they exhaust soils much less than any of the other plants named. 

 Even this would not be a fair comparison, as the roots are in their 

 green state, and therefore contain a very large per cent of water in 

 1,000 pounds, while the others are dry, and require no such deduc- 

 tion. As they stand in the tables above, the plants named in them, 

 would rank as exhausters of the soil as follows, the least exhausting 

 named first : Turnep, potato, rye, wheat, hay or grass, carrot, 

 peas, red clover, barley, oat, white clover. It must be admitted, 

 however, that very much is depending on the state of the plant, so 

 far as regards its maturity, as in most plants the earthy constituents 

 vary much at different periods of their growth. Saussure found in 

 plants of wheat in the same field, that one month before flowering, 

 the ash was 8 per cent ; when in flower 5 .4, and when ripe 3.3 per 

 cent ; and Mollerat found that the potash in the stalk or leaf of the 

 potato diminishes rapidly as the plant approaches maturity. It is 

 worthy of inquiry, however, whether this diminution does not, in 

 part at least, arise from a portion of these earthy matters being ap- 

 propriated to the growth and perfection of the seed or tubers. It 

 is also true that the same variety of plant, on different soils, will con- 

 tain more of any particular substance, as the soil happens to be fa- 

 vorable, or otherwise, for the appropriation ; and not only the quan- 

 tity of any given substance will vary, but the amount of ash, or the 

 sum total of earthy substances, will differ essentially, according to the 

 soil. Prof. Johnston examined specimens of oats grown on boggy 

 peat land, and on sound stiff land, and found that while the quantity 

 of ash was nearly the same in both specimens, the silica from the 

 sound land was 3 .42 per cent, and from the boggy only 1 . 90. Grain 

 grown on soils where the silica is deficient, generally has weak straw 

 and lodges badly ; while a good supply of silica, gives a stiff sound 

 straw, and secures in a greater degree the perfection of the seed. 

 Wheat straw varies in a rem-arkable degree in the quantity of ash pro- 

 duced, but as a general rule, the surer the soil for wheat, the greater 

 the proportion given. Thus, Saussure, from 100 pounds of ripe 

 wheat straw, obtained 4.3 pounds ash; Sprengel, 3.5; Bathier, 



