AVAILABILITY OF DIFFERENT PHOSPHATES APPLIED TO 
HAWAIIAN SOILS. 
SOIL TYPES USED. 
Three types of soil, one of which was thought to be very deficient 
in phosphoric acid were used. The following table shows the chem- 
ical composition of the soils as determined by digestion with hydro- 
chloric acid of specific gravity 1.115: 
Table I. — Composition of soils used in the experiments. 
Soil 
No. 3. 
Moisture 
Volatile matter 
Insoluble matter 
Ferric oxid (Fe 2 03) 
Alumina ( A1 2 3 ) 
Titanium oxid (Ti0 2 ) . . . 
Manganese oxid (M113O4) 
Lime(CaO) 
Magnesia (MgO) 
Potash (K 2 0) 
Soda(Na 2 0) 
Sulphur trioxid (S0 3 ) . . . 
Phosphoric acid (P 2 5 ) . . 
Soil 
Soil 
No. 1. 
No. 2. 
Per cent. 
Per cent. 
7.65 
12.61 
8.42 
12.19 
38.49 
36.74 
16.63 
15.96 
12.85 
17.52 
2.00 
3.50 
.24 
.08 
1.84 
.18 
8.71 
.34 
.39 
.34 
1.36 
.28 
.08 
.44 
.57 
.28 
Per cent. 
4.02 
15.33 
31.60 
21.28 
21.37 
3.60 
.20 
.50 
.64 
.35 
.35 
.32 
.29 
Soil No. 1 represents the type to be found in and about Honolulu. 
It has a sandy texture and is derived in part from the disintegration 
of black volcanic ash. It is used for truck gardening, rice, and 
bananas. 
Soil No. 2 is the highly ferruginous type of red clay so abundant in 
the islands. 
Soil No. 3 is a red soil very similar to No. 2, differing in that No. 3 
has a better texture, that is, less clay. 
METHOD. 
The method used in preparing the pots was similar to that pro- 
posed by the Basic Slag Committee of the Association of Official 
Agricultural Chemists. Tin pots were used instead of clay pots in 
order to eliminate the loss of fertilizer through efflorescence. Each 
pot contained 6 pounds of soil. The forms of phosphate used were: 
Double superphosphate (46.25 per cent P 2 5 ), acid phosphate (19.49 
per cent P 2 5 ), four different Thomas phosphate slags (A, 18.38 per 
cent P 2 5 ; B, 19.04 per cent P 2 5 ; C, 13.31 per cent P 2 5 ; D, 15.86 
per cent P 2 5 ), phosphate rock (29.4 per cent P 2 5 ), commercial 
sodium phosphate (20.87 per cent P 2 5 ), trimagnesium phosphate 
(54.1 per cent P 2 5 ), tribasic potassium phosphate (33.4 per cent 
P 2 5 ), dibasic potassium phosphate (40.8 per cent P 2 5 ), monobasic 
potassium phosphate (52.2 per cent P 2 5 ), reverted phosphate (18.56 
per cent P 2 5 ), bone meal (27.76 per cent P 2 5 ), ferrous phosphate 
(37.8 per cent P 2 5 ), ferric phosphate (31.8 per cent P 2 5 ), aluminum 
phosphate (58 per cent P 2 5 ), and titanium phosphate (34.1 per cent 
