28 MANURING EXPERIMENTS WITH PADDY RICE (SECOND YEAR). 
the peculiar deportment of the sodium phosphate towards our 
soil. Owing to the richness of the latter in hydrated sesqui- 
oxides of iron and alumina the phosphoric acid of this salt 
is speedily precipitated, especially if it is applied as it was in 
these experiments, in the dissolved state ; and in the precipitate 
the sesquioxides will, of course, predominate the more, the 
less phosphoric acid is incorparated with the soil. Thus, with 
large doses of sodium phosphate, the products of the absorp¬ 
tion in the soil are of a less basic character and can accordingly 
be more easily and completely taken up by the roots than if 
small doses were applied. The active ingredient of superphos¬ 
phates, i. e. monocalcium phosphate, on the other side, is not 
so soluble in water; therefore the solid particles when put into 
the soil come into contact with a less quantity of sesquioxides 
and yield besides dicalcic phosphate compounds of a less basic 
condition than the sodium phosphate. Hence the phosphoric 
acid of the superphosphate must have in soils like ours a better 
effect than sodium phosphate. For the same reason the 
granulation of superphosphates is, to some extent, connected 
with the effect. In a very finely pulverized state and if well 
mixed with a soil rich in sesquioxides, they may favour too 
much the formation of basic phosphates and thus become less 
effective than the more coarsely granulated kinds. Researches 
by P. Wagner 13 on a sandy soil very poor in lime with finely 
powdered and coarse particles of superphosphate (the latter 
having a diameter of 1.5-2 millimetres), proved, indeed, the 
action of the former to be about 60% lower than that of the 
latter, but this author holds the excessive distribution alone 
to be responsible for the inferior action of the fertilizer, where 
as our experiments give evidence that the chemical condition 
of the products of the absorption in the soil may also vary 
according to the size of the particles, and may likewise account 
for his result. 
In our researches the best effect on rice was exerted by the 
13 Important practical questions on the subject of manures, 1885, p. 48. 
