MANURING EXPERIMENTS WITH PADDY RICE (SECOND YEAR). 
2g 
precipitated calcium phosphate, which consisted chiefly of 
dicalcium phosphate ; and very nearly the same action was 
displayed by the superphosphate the greater part of which 
was made up of monocalcium phosphate. A slight superiority 
of the former over the latter has already been noticed by 
numerous authors among whom we may mention A. Peter- 
mann, 11 L. Grandeau, 15 J. Fittbogen, 16 E. Wein, 17 and M. 
Mærker 1 “. In general it appears from these experiments 
that on those soils which exhibit an extreme deportment 
towards soluble phosphates i.e. which have either a very low, 
or a very high absorptive power for their nutrient, the dicalcium 
phosphate or reverted phosphates act better than the monocal¬ 
cium phosphate of superphosphates. Where the absorptive 
power is very low, the soluble phosphoric acid may diffuse 
through so large a volume of soil that the roots cannot extract 
enough of it; and, on the other side, if the soil is very rich in 
absorbent constituents a considerable formation of basic phos¬ 
phates may take place, which yield their phosphoric acid to 
the roots with difficulty. The superphosphates are therefore 
suited principally for soils of a medium condition, while the 
dicalcium phosphate (precipitate) can be used for all kinds of 
soils. The manufacture of precipitated phosphates has lately 
been so improved that a content of 35 and even 42% of 
phosphoric acid almost completely soluble in ammonium citrate 
is guaranteed by the factories ; and as in spite of their richness 
and great efficacy these phosphates sometimes command lower 
prices than superphosphates, they deserve to be recommended 
for importation. Although only faintly soluble in water, their 
distribution in paddy fields will not be difficult in Japan where 
the preparation of the fields is so careful and the soil is worked 
on to a sufficient depth. The quantity of phosphoric acid to 
14 Landvv. Versuchsstationen, vol. 24, p. 321. 
15 Biedermann’s Centralblatt für Agriculturchemie, vol. 7, p. 650. 
16 Ibid. vol. 14, 18 p. 313. vol. 7, p. 650. 
17 Ibid. vol. g, 18 p. 647. 
18 Ibid. vol. 10, 18 p. 37S. 
