20 MANURING EXPERIMENTS WITH PADDY RICE (THIRD YEAR). 
cessible to the roots. Even the bone ash and powdered phos¬ 
phorite had less effect in the second season, though we might 
have anticipated that they would have become more active, as 
the richness of our soil in humus of a distinctly acid character 
favours the decomposition of insoluble calcic phosphate. The 
best after-effect was displayed, as already stated, by the two 
kinds of bone dust and the Thomas phosphate. The increase 
of grain caused by the residues of these manures in the second 
season amounts, in the case of stfeamed bone dust and Thomas 
phosphate, to about 70% of the increase in the first season, in 
the case of crude bone dust to nearly 50%. 
In order to obtain definite figures as to the efficacy of the 
various phosphates in the two seasons we calculate from the 
preceding tables and from the results recorded in bulletin No. 
10, p. 22 the following numbers, taking into account only the 
yields caused by the smaller doses of phosphoric acid, for the 
reasons formerly 7 given. 
Increase of grain in the Relative increase, action 
two first seasons of superphosphate = ioo 
per plot 
grms. 
caused by ioo grms. 
of phosphoric acid 
originally applied grms 
in the two 
seasons. 
in the first 
season. 
Double Superphosphate . 
274 
7°44 
IOO 
IOO 
Precipitated Phosphate . 
356 
7758 
no.7 
107.1 
Peruvian Guano 
. 268 ' 
3845 
54.6 
33-3 
Thomas Phosphate .. 
• 346 
5025 
71.2 
48.8 
Steamed Bone Dust.. 
• 37 1 
5388 
7 6 -5 
53 -o 
Crude Bone Dust 
360 
5228 
74.2 
t-n 
VO 
bo 
Bone Ash . 
• 159 
2309 
32.6 
29.I 
Phosphorite . 
. 96 
1394 
18.3 
11.8 
Before discussing these results we may take into account 
the quantities of phosphoric acid consumed from the residual 
phosphates. The chemical analyses of the crops gave the 
following results per frame : 
7 Bulletin No. 10, p. 22. 
