DOLOMITE AND ZINC INTERACTIONS'IN TWO
PEANUT CULTIVARS m t
F. M. Rhoads, F. M. Shokes, and D. W. Gorbet
North Florida Research and Education Center
University of Florida
SFlorida Agricultural Experiment Stations
Institute of Food and Agricultural Sciences
E -S-Bi-S 2 ,- University of Florida, Gainesville
Research Report 91-6
Dolomite and Zinc Interactions in Two
F.M. Rhoads, F.M. Shokes, and D.W. Gorbet
Previous research (Rhoads et al., 1989) indicated a difference
between Sunrunner and Southern Runner peanut cultivars in response
to zinc (Zn) fertilization. Southern Runner was more sensitive
than Sunrunner to Zn deficiency. Zinc toxicity occurred in both
cultivars with soil-test Zn above 8 lb/acre and soil-test calcium
(Ca) levels below 400 lb/acre. However, no toxicity symptoms were
observed with soil-test Ca above 800 lb/acre and soil-test Zn above
Soil pH was shown to influence leaf Zn concentration of
peanuts in North Carolina (Cox, 1990). Leaf Zn decreased as soil
pH increased. The Ca/Zn ratio in young mature leaves of peanut was
found to be related to Zn toxicity symptoms in Georgia studies
(Parker et al., 1990). Zinc toxicity symptoms were observed in
plants with a Ca/Zn ratio below 50 and no symptoms were found in
plants with a ratio above 50. Lime and Zn interactions in peanuts
were not documented in the North Carolina and Georgia reports (Cox,
1990; and Parker et al., 1990).
The objective of this research was to examine interactions and
main effects of dolomite and Zn on dry-matter yield, tissue Zn,
tissue Ca, and tissue Mg of Sunrunner and Southern Runner peanut
cultivars. Also, the relationships between soil-test Zn and
applied Zn and between dry-matter yield and Ca/Zn ratio in peanut
tissue were determined.
METHODS AND MATERIALS
Soil was collected in plastic containers from the Ap horizon
of Norfolk loamy sand (fine-loamy, siliceous, thermic, Typic
Kandiudults) from an unfertilized area on the North Florida
Research and Education Center, Quincy. The soil was dried,
screened (with a non-metal screen) and weighed into plastic pots
(6.0 kg per pot). Each pot of soil was mixed with 2 g of 46%
triple superphosphate, 3.0 g of potassium sulfate, 4 g of ammonium
nitrate and the amounts of dolomite and Zn shown in Table 1.
Peanuts (Sunrunner and Southern Runner) in pots of the above mix,
were grown in a greenhouse for approximately nine weeks with three
levels of Zn (0,5 and 25 mg/kg) and three levels of dolomite (0,6,
and 12 g/pot) in four replications.
At the end of the growing period the above ground portions of
all plants were harvested, dried, and weighed. After weighing,
plant samples were ground, ashed in a muffle furnace at 500C and
taken up in dilute acid (HC1). Solution Zinc was determined with
atomic absorption (AA) spectroscopy and Ca and Mg were determined
with flame emission (FE) spectroscopy.
Soil samples were also collected from pots at the end of the
growth period and extracted with Mehlich-I soil extractant. Soil
pH was measured in a 1:1 v/v soil-water suspension.
The experimental design was a randomized complete block with
treatments arranged factorily (2x3x3), containing two cultivars,
three levels of Zn, and three levels of dolomite. Analysis of
variance procedures were used to evaluate main effects and
interactions of treatment factors. Regression analyses were used
to evaluate soil-test Zn and Ca/Zn ratio in peanut tissue (Steel
and Torrie, 1960).
RESULTS AND DISCUSSION
Main effects of cultivar and lime rate on dry-weight of
Sunrunner and Southern Runner peanuts were not significant (P>0.05)
(Tables 1 and 2). Dry-weight was significantly (P<0.01) reduced
with 50 lb Zn/acre (25 mg/kg) in both cultivars at all lime rates.
Interaction between cultivar and lime rate was significant (P<0.05)
for dry-weight as shown by maximum yield of Sunrunner at 6 g/kg
lime and maximum yield of Southern Runner at 12 g/kg lime.
Cultivar and Zn rate interaction on dry-weight was shown by a
higher yield of Southern Runner at the 25 mg/kg Zn rate than that
of Sunrunner. Lime significantly (P<0.01) increased dry-weight at
25 mg/kg Zn.
Sunrunner contained the highest average tissue Zn
concentration, 53 ppm versus 44 for Southern Runner (Tables 1 and
2). Zinc concentration in tissue decreased with added lime and
increased with added Zn. Cultivar by Zn interaction and lime by Zn
interaction were shown by variation in slope of tissue Zn versus
Dry-weight, tissue Zn, Ca, and Mg concentration, and
Ca/Zn ratio of Sunrunner and Southern Runner peanuts with
three levels of dolomite and Zn; and soil pH at harvest.
Applied to Soil
Dolomite Zinc Dry-weight Zn Ca Mg
g/pot mg/kg g/pot ppm % % Ca/Zn Soil-pH
0 0 51 10 0.83 0.49 885 5.6
0 5 49 32 0.67 0.44 235 5.5
0 25 4 177 0.54 0.43 31 4.8
6 0 50 7 0.79 0.77 1282 5.7
6 5 51 21 0.70 0.66 335 5.9
6 25 23 103 0.51 0.53 50 5.6
12 0 44 5 0.76 0.87 1738 5.9
12 5 46 26 0.71 0.89 348 5.9
12 25 8 94 0.60 0.63 64 5.7
0 0 45 10 0.64 0.46 690 5.6
0 5 48 31 0.64 0.44 205 5.4
0 25 8 141 0.42 0.39 30 5.2
6 0 37 8 0.68 0.64 1108 5.6
6 5 41 21 0.70 0.58 349 5.8
6 25 26 103 0.57 0.57 57 5.6
12 0 43 6 0.72 0.71 2369 5.8
12 5 43 17 0.73 0.67 487 6.0
12 25 31 62 0.57 0.63 93 6.0
Table 2. Analysis of variance for peanut dry-matter yield, and
tissue concentration of Zn, Ca, and Mg.
Source df Yield Tissue Zn Tissue Cat Tissue Mgt
Cultivar 1 N.S. ** N.S. **
Lime Rate 2 N.S. ** N.S. **
Zinc Rate 2 ** ** ** **
CvxLR 2 N.S. N.S. N.S.
CvxZnR 2 ** ** N.S. N.S.
LRxZnR 4 ** ** N.S. N.S.
CvxLRxZnR 4 N.S. N.S. N.S. N.S.
tLime source was dolomite; N.S. = not significant
*'indicate significance at P = 0.01 and 0.05, respectively.
Zinc rate was the only treatment factor that influenced peanut
tissue Ca (P<0.01). Tissue Ca decreased with increased Zn.
Sunrunner contained a higher average tissue Mg content that
Southern Runner (Tables 1 and 2). Addition of dolomite increased
tissue Mg whereas Zn addition decreased it.
The Ca/Zn ratio in peanut tissue was below 100 in all
treatments receiving 25 mg/kg added Zn (Table 1). The critical
level of Ca/Zn ratio was 140 for this experiment (Fig. 1) compared
to a value of 50 in Georgia tests (Parker et al. 1990). However,
there is not necessarily a conflict between our data and Georgia's
because our critical level was based on dry-weight while theirs was
based on presence or absence of symptoms of Zn toxicity. We used
whole plants for chemical analysis and they used youngest mature
leaves. Furthermore, five out of six treatments showing Zn
toxicity in our tests had Ca/Zn ratios below 65.
Zinc concentration in peanut tissue did not change much with
soil pH at zero and 5 mg/kg Zn rates (Table 1). However, soil-pH
accounted for 66% of the variation in Zn concentration at the 25
mg/kg Zn rate. Peanut tissue Zn concentration changed an average of
78 ppm per unit of change in soil-pH with the 25 mg/kg Zn rate.
The following equation, ppm Zn = 540-78(soil-pH), predicts that
soil-pH above 6.3 would result in Zn concentrations below 50 ppm
for the 25 mg/kg Zn rate. A liming test in North Carolina showed
very little change in peanut tissue Zn in the soil-pH range of 5.0
to 6.2 with non-toxic levels of Zn (Cox, 1990).
Rate of applied Zn accounted for 92% of the variation in soil-
test Zn level in this experiment (Fig. 2). The Mehlich-I
extractant removed an average of 22% of the Zn added as ZnSO4. Dry-
weight of peanuts was related to Zn rate by the following equation:
Y = 44.9+0.622X-0.0703X2; where Y = dry-weight of peanut plants in
g/pot and X = Zn rate in ppm (mg/kg). Maximum dry-weight was
predicted from the above equation to occur at 4.42 ppm Zn applied
to the soil which is equivalent to 2.02 ppm soil-test Zn from the
equation in Fig. 2. Five pounds of extractable Zn per acre was
adequate for maximum growth of peanuts in this test.
Yield of peanuts and peanut tissue calcium concentration were
not affected by cultivar and dolomite. Sunrunner contained the
highest Zn and Mg concentrations in the tissue. Dolomite decreased
peanut tissue Zn and increased tissue Mg. A Zn rate of 50 lb/acre
(25 mg/kg) reduced yield and tissue concentration of Mg and Ca.
Tissue Zn concentration in peanuts was directly related to rate of
Zn application and inversely related to soil pH. Interactions
between cultivar and Zn rate and between dolomite and Zn on yield
and tissue Zn were highly significant.
Dry-weight vs Ca/Zn in Peanuts
50 xx x
x Trt Means
0 x L-P Model
Y -1.67 + 0.338X X < 140
Y 45.65 X = or > 140
0 I I I
400 600 800
Calcium/Zinc Ratio in Tissue
Figure 1. Relationship between peanut plant dry-weight and Ca/Zn ratio in plant
tissue. Data points are treatment means. A linear-plateau (L-P) model
is shown as determined from regression analysis.
Regression Zinc Rate
Soil-Test Zinc (ppm)
0 5 10 15 20 25 30
Zinc Rate (ppm)
Figure 2. Regression analysis of soil-test zinc on rate of Zn applied to the soil.
1. Cox, F.R. 1990. A note on the effect of soil reaction and
zinc concentration on peanut tissue zinc. Peanut Science
2. Parker, M. B., T. P. Gaines, M. E. Walker, C. O. Plank, and J.
G. Davis-Carter. 1990. Soil zinc and pH effects on leaf zinc
and the interaction of leaf calcium and zinc on zinc toxicity
of peanuts. Commun. In Soil Sci. Plant Anal. 21(19 &
3. Rhoads, F. M., F. M. Shokes, and D. W. Gorbet. 1989.
Response of two peanut cultivars to soil zinc levels. Univ of
Fla (IFAS), NFREC, Quincy Res. Rpt. 89-2.
4. Steel, R. G. D., and J. H. Torrie. 1960. Principles and
procedures of statistics. McGraw-Hill, New York.