Page 368
193
To gain knowledge on these questions, ten phosphatic materials were tested in a series of experiments. They were applied broadcast at 0.5 cwt. P2Os_per acre, and compared with a superphosphate scale at 0.2, 0.4 and 0.8 cwts. PO, per acre.
Two plots receiving no phosphate were incorporated in each of the two randomised blocks in each experiment. Plot size was 0.0125 acre. N dressings. were made up throughout to 0.117 cwt. per acre with sulphate of ammonia, and limestone at 8 cwt. per acre was given. to all plots on sites where analysis. indicated a possible deficiency of Ca.
The materials tested, the water and citric solubilities of the phosphate they contained, and the mean response in six experiments at Kongwa are shown in Table 10.
The
The ammonium phosphate was Canadian; the mixture of sulphate of ammonia. and triple superphosphate was a commercial mixture prepared in Holland; the nitrophosphate was prepared experimentally at R.O.F. Pembrey, Wales. Uganda rock was a sample from Tororo in Uganda, and the soda phosphate was prepared from the same batch by a rotary kiln heat treatment at the laboratories of the E.A. Industrial Research Board in Nairobi. Gafsa and Christmas Island rock phosphate were the normal commercial products from those places. Saphos is an Egyptian rock phosphate similar in many ways to Gafsa, and the Gafsa plus superphosphate mixture was made of equal parts by weight of the two components.
Table 10.-Composition of Materials used in Experiments on Types of Phosphate, together with Mean Responses in lbs. Kernels per Acre in six Experiments on: Groundnuts, Kongwa, 1947-48
Total Total
Material
Condition
N P205 P205
Water Citric soluble soluble P2O5
Water Citric soluble soluble P205 P2O5
Mean response
at
as
as
Kongwa
per per cent. cent.
per
per
per
per
(kernels,
cent.
cent.
cent. cent.
lbs./
total
total acre)
P205
P2Os
1
Superphosphate.
Triple superphosphate +sulphate of am-
2
3
4
5
6
7
8
9
...
powder
19.7 18.4
19.3
93.4 98.0
27
monia
granular
6.3 30
30
Ammonium phosphate | granular
Triple superphosphate | granular
Soda phosphate
powder
22.2
0.0
30
11. 48.7 48.0 48.3 98.5 99.0
46
38.9 39.5 92.6
15.8
100 100
60
75
98-8
80
0.0 71.2
48
Gafsa superphosphate
mixture
...
...
powder
24.1
10.2 15.2
42.3
63.1
46
Nitrophosphate
Saphos rock phosphate powder
granular
5
30
3.1 18.0
10.3
60.0
16
26.2
0.0
10.2
0.0
38.6
50
Gafsa rock phosphate
powder
27.3
0.0
10.4
0.0 38.1
58
Christmas Island rock
phosphate
powder
37.7
0.0
11.3
0.0 30.0
19
Uganda rock phosphate
powder
24.5
0.0
4.1
0.0 16.7
2
Page 368,of 1097
Page 368
Details of the six experiments at Kongwa are given in Table 11.
131
:ཀ 1
[1
་
¡
] [
(
JI
1.