MANURING EXPERIMENTS WITH PADDY RICE (SECOND YEAR). 
13 
phosphoric acid. Similar results were arrived at in the 
determination of the amount of phosphoric acid that was taken 
up by the plants from the residues in the soil, as is shown by 
the following figures : 
Phosphoric acid, grms. 
In the whole crop of 
1890. 
In the crop of 1890 
produced without 
phosphoric acid 
I. • 
0.84 
0.88 
2. 
0.86 
0.88 
3- 
1.36 
0.88 
4 - 
1.71 
0.88 
5- 
2.11 
0.88 
6. 
2.44 
0.88 
Freshly 
manured. 
2 - 73 . 
0.88 
Consumed from the 
residual phosph. acid 
left by the crop of 
1889. 
0.48 
0.83 
1.23 
1.56 
1.85 
Residue of phosphoric 
acid from 1889 
3- 6 5 
6.99 
10.86 
14.81 
19-32 
23.29 
18-36 
Consumed, per cent 
of this residue 
_ 
4.42 
5.60 
6-37 
6.70 
10.06 
Thus, the residues left from the two smallest doses of pho¬ 
sphoric acid were no longer available at all to the subsequent 
crop, while from the unexhausted portions of larger doses, con¬ 
siderable quantities were assimilated. But the freshly applied 
phosphate was distinctly more accessible to the plants than 
the residues left from the preceding year. 
In these facts there is clear evidence that some of the 
residual phosphoric acid must have either been washed away 
by irrigation or rain, or have assumed a state in which it could 
no longer be dissolved by the roots or agencies in the soil. 
Without denying that both these processes may have taken 
place, several facts appear to indicate that the conversion into 
a'n insoluble state was the principal cause of the inacces¬ 
sibility to the roots of the residual phosphate. Indeed, when 
sodium phosphate is incorporated with a soil so rich in hydrated 
sesquioxides of iron and alumina as ours, the greater part of 
the phosphoric acid at once yields basic phosphates with these 
