The Journal of the Department of Agriculture, Victoria . imes more phos-phoric acid than is required for one wheat crop. But the roots have no-openings and they must absorb their ash constituents in solution and the-great bulk of phosphoric acid in soils is insoluble in water. Given suf-ficient soil moisture and good physical condition it is the most deficientsoil constituent which determines the size of the crop, and for this reasonit is usual to supply a little soluble phosphoric acid in superphosphates toimprove the soil in its weakest point. Soils may be classed as sand, clay, lime and pea
The Journal of the Department of Agriculture, Victoria . imes more phos-phoric acid than is required for one wheat crop. But the roots have no-openings and they must absorb their ash constituents in solution and the-great bulk of phosphoric acid in soils is insoluble in water. Given suf-ficient soil moisture and good physical condition it is the most deficientsoil constituent which determines the size of the crop, and for this reasonit is usual to supply a little soluble phosphoric acid in superphosphates toimprove the soil in its weakest point. Soils may be classed as sand, clay, lime and peat or humus soils. As^regards the grain the ash varies little in composition according to thesoil. The straw however varies considerably—£.g-, on clay soil the ashmay contain about 70 per cent, of silica, on peat hardly any. A 20-bushelcrop of wheat may contain 35 lb. nitrogen, 14 lb. phosphoric acid, and:20 lb. of potash, the first two being chiefly in the grain and the the straw. 190 Joiinial of Agriculture, Victoria. [10 March. While the composition of the ash of the whole crop varies according-to the soil it is grown on, it is evident that the crop exercises to some extent a power of selection, absorb-ing in largest quantity thoseparticular constituents whichit requires :—Thus the ashof wheat contains a rela-tively high percentage ofphosphoric acid and a lowpercentage of lime. Theash of mangolds, on theother hand, is rich in potash,whilst that of clover andlucerne is rich in lime. Whatprobably happens is that thenutrient solution for anygiven soil is more or less ofconstant composition. Theroot hairs allow this soilsolution to enter by osmosisuntil the concentration insidethe cell is the same as that17. EPIDERMIS OF FED-RATION WHEAT ^^j^j^^^^^ No mote Can enter (under SURFACE OF LEAF) SHOWING ^^^^-j ^j^^ jj^^j^^g ^^jj^ ^f ^^^ STOMATA (3321 PER SQUARE CENTi- ^^^^^^ withdraw some of themetre). nutrient solution for con- structi\e purposes and thus low
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectagricul, bookyear1902
