Agriculture Reference
In-Depth Information
and Lotse (1974) reported that the exponent of the
Freundlich equation was independent of the time and
temperature, and the values depended on P concentration
in the solution. In the Freundlich equation
a
could be
considered as a capacity factor, implying that a soil having
a larger value of
a
has a greater adsorbing capacity than
a soil having a smaller value. In the present study, clay
loam soil had the highest
a
value followed by sandy
clay loam and sandy loam soils, respectively. These
equations showed that adsorption decreased exponen-
tially with increasing saturation of exchange sites. Samadi
(2003) reported that P adsorption in calcareous soils was
significant at relatively high P concentrations only due
to CaCO
3
.
17.3.3 Green fodder yield (Mg/ha)
17.3.3.1 Sandy clay loam soil
Data on total green fodder yield of berseem from five
cuttings for three soils are presented in Table 17.5. The
P doses for obtaining maximum green fodder yields
were different for the three soils. In the case of sandy
clay loam soil, the maximum yield in the first and sec-
ond cuts was observed at the solution level of 0.30 mg
P/L, which was achieved by adding 92 kg P/ha, while
Table 17.4
P doses by Freundlich adsorption model for the
three soils.
Target P
conc. (mg/L)
Sandy clay loam
Clay loam
Sandy loam
P (kg/ha)
17.3.2 Computation of p doses using
the Freundlich equation
Equivalent to the specific solution levels (0.05, 0.10,
0.15, 0.20, 0.25, 0.30, 0.35, 0.40 and 0.50 mg P/L),
fertilizer doses were calculated by using a linear form
of the Freundlich equation (Table 17.4) for the three
soils. The P quantities, computed as mg P/kg, were dif-
ferent for sandy clay loam, clay loam and sandy loam
soils. It was evident that different soils require a differ-
ent P rate to maintain the same target P solution
concentration.
0.00
0
0
0
0.05
32
58
44
0.10
48
78
58
0.15
61
83
68
0.20
73
105
76
0.25
83
116
83
0.30
92
125
89
0.35
100
133
94
0.40
109
141
99
0.50
124
155
108
Table 17.5
Green fodder yield in ive cuttings of berseem (1st crop) on sandy clay loam soil.
Target P conc. (mg/L)
P (kg/ha)
Yield (Mg/ha)
1st cut
2nd cut
3rd cut
4th cut
5th cut
Total
0.00
0
13.66 e
18.01 f
14.56 f
17.74 d
10.44 e
74.53 f
0.05
32
16.33 d
21.11 e
17.78 e
21.57 c
11.56 e
88.46 e
0.10
48
17.14 d
21.42 de
20.78 d
21.66 c
14.78 d
96.44 d
0.15
61
19.52 c
22.26 cde
21.60 cd
22.91 bc
15.56 cd
102.11 c
0.20
73
20.08 c
23.00 bc
22.39 bc
23.00 bc
16.44 c
105.10 c
0.25
83
22.23 b
24.01 b
22.70 abc
23.14 bc
18.04 b
110.10 b
0.30
92
24.19 a
25.74 a
23.63 ab
23.83 b
19.16 ab
116.51 a
0.35
100
23.28 ab
24.08 b
24.11 a
25.81 a
20.28 a
116.91 a
0.40
109
22.23 b
23.28 bc
23.43 ab
24.16 b
19.97 a
113.12 b
0.50
124
21.89 b
22.69 bcd
22.29 bc
23.71 b
19.44 a
112.53 b
CV (%)
5.82
5.43
5.7
5.76
6.83
2.81
LSD
1.358
1.439
1.412
1.523
1.315
3.382
Means sharing same letters are statistically ≤5% level of probability.
CV, coefficient of variation; LSD, least significant difference between treatment means.
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