Soil testing makes the difference
An Incitec Pivot Fertilisers trial at Marcus Hill near Geelong shows
the value of soil testing as a basis for fertiliser decisions.
In May 2007, a soil test at the site showed phosphorus levels of
17 mg/kg (Colwell P) with a PBI of 130 and sulphur levels of 18
mg/kg (KCL-40).
This means the site was probably producing at 80-90% pasture
performance compared with potential and would respond to
fertilisers, such as SuPerfect®.
See critical phosphorus ranges table below. See over for more
about this trial.
“Incitec Pivot Fertilisers’ trial at
Marcus Hill shows the responses to
a range of fertiliser treatments and
the change in soil phosphorus levels
with annual fertiliser applications.”
Table 1: Critical phosphorus ranges for a beef or sheep system aiming for 90-95% potential yield
Soil test guidelines for 0 - 10 cm samples in relation to pasture performance goals
Beef or sheep type system aiming for 90 - 95% potential yield at “Adequate” soil test result
Pasture performance compared
to potential
<80%
80% - 90%
90% - 95%
95% - 98%
>98%
Deficient - capital
fertiliser required
Marginal –
fertiliser required
Adequate
– maintenance
fertiliser required
High - possible
low fertiliser
manintenance
Very high - no
fertiliser required
15 - 22
>22
Olsen P (mg/kg)
All soils
<8
8 - 12
12 - 15
Colwell P (mg/kg)
PBI 0-15 (Very sandy)
<11
11 - 18
18 - 23
23 - 30
>30
PBI 15-35 (Sand, Sandy loams)
<12
12 - 20
20 - 26
26 - 34
>34
PBI 35-70 (Sandy/Silty loams)
<14
14 - 23
23 - 30
30 - 39
>39
PBI 70-140 (Sandy/Silty clay loams)
<16
16 - 27
27 - 35
35 - 45
>45
PBI 140-280 (Clay loams )
<19
19 - 32
32 - 42
42 - 54
>54
PBI 280-840 (Clay loams & clay)
<27
27 - 44
44 - 58
58 - 75
>75
PBI >840 (Volcanic clays & peat)
<40
40 - 60
60 - 80
80 - 120
>120
Source: Gourley CJP, Melland AR, Waller RA, Awty IM, Smith AP, Peverill KI, and Hannah MC (2007) ‘Making Better Fertiliser Decisions for Grazed Pastures in Australia’ Victorian
Government Department of Primary Industries.
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