Phosphatic Manures for Root-Crops. 51 
Absorption of Soluble Phosphate by a stiff Clay Surface Soil. 
Experiment D. — The surface soil resting on the preceding 
clav subsoil, on analysis, was found to consist in 100 parts of — 
Water .. ' 3-&1 
Organic matter and water ol" combination . . . . 4 80 
Oxides of iron and alumina 7'85 
Phosphoric acid '04 
Carbonate of lime 2-08 
Sulphate of lime '15 
Magnesia and alkalies .. '32 
Insoluble siliceous matter (clay) 80'85 
100-00 
5000 grains of this SoS, llO-G-t grains of Superphosphate {containing 41 15 
grains of Soluble Phosphate), and 21,000 grains of Distilled Water, icere 
mixed as in the previous Experiments. 
After 24 hours, 7000 grains of liquid being drawn ofl', were found to con- 
tain 6 9 grains of phosphate, so that the whole 21,000 grains 
held in solution 20" 70 grains. Hence the soil had absorbed 
20'45 grains or very nearly half the soluble phosphate. 
After 8 days (there being now 14,000 grains in the bottle) 7000 grains were 
dravvn ofl", and found to contain 5'40 grains, so that the 
14,000 grains held in solution 10 80. Hence the soil had now 
absorbed 23 45 grains. 
After 17 days, it was found that the 7000 grains of water now left in the bottle 
contained 2'14 grains of phosphate, so that the soil had 
absorbed in all 26"71 grains. 
Had tjie whole solution been drawn off' in each of these three successive 
Experiments, it would have contained — 
Grains. 
After 24 hours 20-70 of bone-earth. 
„ 8 days .. 16-20 
,, 17 days 6-42 ,, 
And 12 oz. of soil w ould have absorbed — 
After 24 hours 20-45 „ 
„ 8 days 24-95 „ 
„ 17 days 3i-73 „ 
It ttus appears that the absorption of soluble phosphate took 
place very imperfectly after eight days, and that after seventeen 
days an appreciable quantity of soluble phosphate was still left in 
the liquid. 
Both the surface and clav subsoil, in the proportions in which 
they were used, possessed the power of rendering soluble phos- 
phates insoluble in a far less degree than the chalky soil. 
Absorption of Soluble Phosphate by a light Sandy Soil. 
Experiment E. — The next three experiments will show whether 
the prevailing impression is correct, that on light sandy soils a 
E 2 ' 
