91
Figure 5.6. Effects of the application of K as K
2
SO
4
, gneiss SRF, and K-feldspar SRF on cumulative yield oven-dried plant tops and cumulative K uptake for the 1
st
, 2
nd
, 3
rd
, and 4
th
harvests H1, H2, H3, and H4 of ryegrass grown on soil SCP-11. The broken lines are drawn from best fit equations Table 5.5 describing
relationships between application rate of K fertilizers and cumulative K uptake. These lines were used to calculate the relative agronomic effectiveness RAE of
SRFs section 5.3.2. Error bars are the standard error of mean.
5.3.2. Concentration of Plant Nutrients in Dry Tops
The application of SRFs may greatly affect concentrations of the major nutrients applied Ca, Mg, and K, but may also affect the concentrations in plants of
non treatment nutrients Na, Cu, Zn, Mn, Fe, Si, P, S, and Cl. It is possible that these effects are due to pH change which may have caused plant nutrition disorders
deficiency or toxicity in this experiment. The results of analysis of variance for effects of the application rate of fertilizers on concentrations of nutrients in dry tops
of ryegrass are presented in Appendix B3.
a K from K
2
SO
4
H1 H2
H3 H4
4 8
12 16
22.5 45
67.5 90
Rate of K mgkg Y
iel d
g p
ot
b K from Gneiss SRF
H1 H2
H3 H4
4 8
12 16
20
225 450
675 900
Rate of K mgkg Yiel
d g pot
c K from K-feldspar SRF
H1 H2
H3 H4
4 8
12 16
20
450 900
1350 1800
Rate of K mgkg Yield g
p o
t a K from K
2
SO
4
H1 H2
H3 H4
10 20
30 40
50 60
70 80
90
22.5 45
67.5 90
Rate of K m gkg K
up tak
e m
g pot
b K from Gneiss SRF H4
H1 H2
H3
50 100
150 200
250 300
225 450
675 900
Rate of K mgkg K upt
ak e m
g pot
c K from K-feldspar SRF
H1 H2
H3 H4
50 100
150 200
250 300
450 900
1350 1800
Rate of K mgkg K
u p
ta ke
m g
p o
t
92 For Ca experiment using soil WP-6, the effect of application of Ca as CaCl
2
on nutrient concentration in dry tops could not be identified due to insufficient data most plants died. For the +basalt SRF and +dolerite SRF treatments, the
concentration of Ca in dry tops of plants for H1 – H4, Appendix B4 was doubled i.e., from about 0.1 to about 0.2 by increasing the application rate of Ca from
333 to 1332 mgkg. Concentrations of Zn and Mn in dry tops of H2 – H4 increased by about 2 - 3 fold with the increase of application rates of Ca as basalt and dolerite
SRFs. Concentrations of these nutrients reached very high levels, i.e., more than 20 and 200 mgkg respectively for Zn and Mn, but were below toxic levels 40 mgkg
for Zn and 1230 mgkg for Mn Pinkerton et al. 1997. There was no simple trend
in the concentration of other nutrients in dry tops in response to the application of Ca fertilizers.
For Ca experiment using soil MR-5, there was no significant effect of the application of Ca fertilizers on the concentration of nutrients in dry tops, except for
the concentrations of Cl and Si. Concentration of Cl in dry tops of plants increased with increasing rate of CaCl
2
applied. Concentration of Si in dry tops H1 – H4 receiving Ca as basalt and dolerite SRFs were 2 - 3 fold higher than for plants for
the nil Ca or +CaCl
2
treatments. Presumably this was due to the large supply of soluble Si due to dissolution of these SRFs. For Mg experiment using soil MR-5,
there was no significant effect of the application of Mg fertilizers on the concentration of nutrients in dry tops.
For K experiment, the concentration of K in dry tops of plants grown on soils BSN-1 and SCP-11 increased with increasing application rate of K fertilizers. For
the +K
2
SO
4
treatment, this effect occurred only for plant tops from H1 – H2, whereas for the +SRF treatments it occurred for H1 – H4. Concentrations of other
nutrients i.e., Ca, Mg, P, Cl, Cu, and Zn in dry tops for most harvests decreased with increasing application rate of all K fertilizers. Antagonistic interactions of Ca
and Mg with K have been reviewed by Munson 1968 and Marschner 1986 in which high concentrations of K inhibit the uptake and physiological availability of
Ca and Mg for plants. The application rate of SRF as K fertilizers increased the concentration of Si in dry tops as a consequence of large amounts of Si released
from these SRFs.
93 The great increase of plant-available Si in soils due to dissolution of SRFs
indicates an advantage for the use of SRFs for plants that required Si e.g., grasses. Large amounts of plant-available Si in soil may stimulate plant growth and the
quality of plant products Epstein 1999, reduce toxicity effects of Mn Marschner 1986 for several plant species, reduce Al-induced inhibition of corn roots Ma et al.
1996; Corrales et al. 1997, and increase resistance of plants to the attack of several pathogens Volk et al. 1958. Coventry et al. 2001 associated the beneficial effects
of plant-available Si from application of Minplus
TM
crushed basalt to the reduction of Al toxicity in acidic soils.
Nutrient deficiency or toxicity in the ryegrass was identified by comparing the concentration of nutrients in dry tops to the critical values proposed by Pinkerton
et al . 1997 Appendix B4 – B12. Concentration of P in dry tops of ryegrass from
the present experiment was generally lower than the P-deficient level 0.13 proposed by Pinkerton et al. 1997, except for most plants grown on soil SCP-11.
However, there were no foliar symptoms of P-deficiency as described by Turner 1993. The low P concentration in dry tops may be partly due to insufficient supply
of P in soils which was supplied as basal fertilizers, but other workers Hinsinger et al.
1996; Pal et al. 2001; Harley, 2002 have used the same basal P application rate or similar soils for growing ryegrass and have not reported P deficiency. Andrew
and Robin 1971 found that native grass taken from low P soils was less responsive to application of P compared to grasses from other soils. The ryegrass used in this
experiment is a high P efficient cultivar Lolium multiflorum cv Richmond that was developed for use for the highly P deficient soils in south-western Australia, so that
a lower critical level is appropriate but unknown. This explanation is consistent with the observation that the highest yields in this experiment were provided by
plants grown on soil MR-5, but these plants had low concentrations of P 0.1 in dry tops.
The plants grown on soil WP-6 receiving Ca as basalt and dolerite applications were deficient in Ca during 12 months of growing periods see
Appendices B4 – B5. In addition, the plants for H2 and H3 were also deficient in Cu 4 mgkg. It was observed that the plants growing on soil WP-6 were shorter
with thicker leaves than plants growing on soil MR-5. Concentration of nutrients in
94 dry tops of plants growing on soil MR-5, including those for the controls, +Ca and
+Mg fertilizer treatments Appendixes B4 – B7 were at adequate levels. For K experiment, the plants grown on soils BSN-1 and SCP-11 were mostly
deficient in K Appendices B10 and B12 after the first 3 months H2 - H4. This nutritive disorder was accompanied by high concentrations of Na i.e., 1.5 for
the nil K treatment and Cl i.e., 2 for the +K-feldspar SRF treatment in plant tops. Yellowish-green leaves which is a typical symptom of K deficiency Turner
1993; Grundon et al. 1997 were common for plants in experiment C, and were associated with chlorosis which might be due to Na toxicity Pinkerton et al. 1997.
These nutritive disorders were so severe that after the 3
rd
harvest the plants grown on the nil K control soil SCP-11 died. The replacement of K by Na in plant tops was
observed by Marschner et al. 1981 for sugar beet, and this mechanism was apparent in this present experiment see Appendices B9 and B11 for the nil K and
+K
2
SO
4
treatments so that plants severely deficient in K had higher concentrations of Na in their tops.
In summary of this review of the general nutrition status of the experimental plants, the application of SRFs increased concentrations of the nutrients applied in
dry tops of ryegrass grown on soils which were deficient in the test nutrients. Plant response was sometimes associated with either a decrease or increase in the
concentration of other nutrients which sometimes extended to nominally deficient or toxic levels.
5.3.3. Relative Agronomic Effectiveness RAE of SRFs
