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
Although plants on soil WP-6 responded well to the application of Ca as basalt and dolerite SRFs, no RAE values could be calculated due to the death of
most plants supplied with the reference CaCl
2
fertilizer. The application of Ca and Mg fertilizers to soil MR-5 had minor effects on nutrient uptake so that response
functions were poorly defined. Based on Figures 5.3 and 5.5, the RAE values for basalt and dolerite as Ca and Mg fertilizers were about 6 .
These SRFs act more as liming materials than as Ca or Mg fertilizers for plant growing on acidic soils e.g. soil WP-6 with pH about 4.0, but these effects
were minor for plant growing nearly neutral and Ca-rich soil e.g., soil MR-5 with
95 pH about 5.6. The best growth of ryegrass is on soils with pH range of 5.5 – 7.5
Hannaway et al. 1999; Valenzuela and Smith 2002. Table 5.5. The best fit equations describing relationships between cumulative uptake
of K Y, mg Kkg and application rate of K fertilizers X, mg Kkg and RAE values. The RAE value is defined as ratio of slope of the equation for SRF relative
to that for K
2
SO
4
at the application rate X of 90 mg Kkg. Fertilizer Harvest
Equation RAE
K
2
SO
4
Gneiss K-feldspar
H1 H2
H3 H4
H1 H2
H3 H4
H1 H2
H3 H4
Soil BSN-1 Y = 15.1 + 0.39 X R
2
= 0.99 Y = 16.6 + 0.68 X R
2
= 1.00 Y = 18.2 + 0.74 X R
2
= 0.99 Y = 19.9 + 0.77 X R
2
= 1.00 Y = 14.1 + 0.14 X – 129 10
-5
X
2
R
2
= 1.00 Y = 20.3 + 0.50 X – 425 10
-5
X
2
R
2
= 0.96 Y = 30.4 + 0.70 X – 519 10
-5
X
2
R
2
= 0.95 Y = 34.3 + 0.75 X – 526 10
-5
X
2
R
2
= 1.00 Y = 15.5 + 0.06 X – 289 10
-5
X
2
R
2
= 0.92 Y = 19.8 + 0.15 X – 521 10
-5
X
2
R
2
= 0.99 Y = 18.3 + 0.21 X – 558 10
-5
X
2
R
2
= 1.00 Y = 20.1 + 0.25 X – 666 10
-5
X
2
R
2
= 1.00 100
100 100
100
43 86
107 110
17 24
30 34
K
2
SO
4
Gneiss K-feldspar
H1 H2
H3 H4
H1 H2
H3 H4
H1 H2
H3 H4
Soil SCP-11 Y = 2.1 + 0.52 X R
2
= 0.99 Y = 4.1 + 0.66 X R
2
= 0.99 Y = 5.4 + 0.70 X R
2
= 0.99 Y = 5.9 + 0.74 X R
2
= 0.99 Y = 7.8 + 0.24 X – 185 10
-5
X
2
R
2
= 0.95 Y = 14.5 + 0.52 X – 412 10
-5
X
2
R
2
= 0.95 Y = 17.8 + 0.71 X – 548 10
-5
X
2
R
2
= 0.96 Y = 18.4 + 0.78 X – 588 10
-5
X
2
R
2
= 0.96 Y = 8.2 + 0.08 X – 225 10
-5
X
2
R
2
= 0.95 Y = 8.3 + 0.14 X – 327 10
-5
X
2
R
2
= 0.99 Y = 9.9 + 0.15 X – 158 10
-5
X
2
R
2
= 1.00 Y = 10.6 + 0.17 X – 150 10
-5
X
2
R
2
= 1.00 100
100 100
100
53 90
116 119
17 23
22 23
96 The best fit equations describing response curves for cumulative K uptake
versus application rate of K fertilizers with their values of RAE are presented in Table 5.5. As shown in this table, gneiss was about half as effective as K
2
SO
4
for growing ryegrass up to 6 months H1 – H2, but was slightly more effective for
plants harvested at 9 and 12 months H3 – H4. This interpretation should be treated with some caution as the plants supplied with K
2
SO
4
had removed most ≈ 34 of
applied K from soil by H2. K-feldspar was much less effective than K
2
SO
4
for all growth periods.
5.3.4. Internal Efficiency IE of Nutrient Elements
