Vol.3, No.5, 674-677 (2012) Agricultural Sciences
http://dx.doi.org/10.4236/as.2012.35082
Reducing toxic effect of seed-soaked Cu fertilizer
on germination of wheat*
Sukhdev S. Malhi#, D. Leach
Agriculture and Agri-Food Canada, Melfort, Canada; #Corresponding Author:
Received 3 June 2012; revised 3 July 2012; accepted 23 July 2012
ABSTRACT
A laboratory incubation experiment (20˚C) was
conducted to find if the detrimental effects of
seed-soaked Cu on wheat seedlings can be mi-
nimized by reducing time duration of seed in
contact with Cu EDTA fertilizer solution. The 24
treatments in a 6 × 4 factorial arrangement in-
cluded 6 rates/amounts of Cu (0, 15, 30, 60, 120
and 240 g·Cu·100 kg−1 seed) and 4 seed-soaking
time durations (0, 4, 8 and 16 h). The germination
of wheat seed was 100% in the zero-Cu control
treatments, irrespective of the duration of seed
soaking time. However, seed germination de-
creased with increasing amount of fertilizer Cu
in the seed-soaking solution, and the magnitude
of reduction in seed germination due to Cu tox-
icity increased with increasing duration of seed-
soaking time in the Cu fertilizer solution. For the
seed-soaked treatments, the detrimental effect
of Cu on germination was greatest with 16 h
soaking, where only 13% - 18% of the seeds
germinated with Cu applied at 15 to 30 g·Cu·100
kg−1 seed. For the 4 and 8 h seed soaking
treatments, germination of wheat seed ranged
from 73% to 83% with 15 g·Cu·100 kg−1 seed
treatment and 42% to 62% with 30 g·Cu·100 kg−1
seed. The findings suggest that the detrimental
effect of Cu on germination of wheat seed
soaked in Cu EDTA solution can be decreased
by reducing duration of soaking time from 16 h
to 4h or 8 h, but this needs further investigation
using soil under growth chamber and/or field
conditions in order to make valid recommenda-
tions for use of this new technology on a com-
mercial scale.
Keywords: Amount/Rate of Cu; Seed-Soaked Cu;
Soaking Time/Duration; Solution Cu
1. INTRODUCTION
Wheat is a very sensitive crop to Cu deficiency [1]. In
the Canadian Prairie Provinces, research has suggested
the use of 3 to 5.6 kg·Cu·ha−1, when granular Cu fertiliz-
ers are incorporated into the surface soil, to prevent Cu
deficiency in crops grown on Cu-deficient soils [2]. For
economic reasons, producers were more interested in
methods of Cu fertilizer application that required low Cu
rates. However, in research studies in Alberta and Sas-
katchewan, granular Cu fertilizers at low rates, either
incorporated into soil up to 2 kg·Cu·ha−1 or seedrow-
placed up to 1 kg·Cu·ha−1, were not effective in prevent-
ing Cu deficiency in wheat in the year of application
[3,4]. This was most likely that the granular Cu fertilizer
applied at low rates did not provide enough “feeding
sites” for optimum wheat growth and seed yield due to
sporadic placement of Cu fertilizer granules in relation to
the growing roots. Previous research has also suggested
the use of low rates of two foliar applications of Cu fer-
tilizers at 0.25 to 0.28 kg·Cu·ha−1 to correct Cu defi-
ciency on wheat in order to maximize seed yield, if it
occurs during the growing season [5].
In order to avoid the inconvenience of foliar applica-
tion, crop damage during in-crop Cu fertilizer application
and for most economic benefits, producers in the Prairie
Provinces were interested in using much lower rates of
Cu fertilizers than previously recommended for foliar or
soil applications. Because Cu is needed in very small
quantities for optimum crop growth, “feeding sites” can
be increased by soaking the seed in dilute Cu fertilizer
solution. Our recent field research showed that Cu defi-
ciency in wheat can be prevented and seed yield in-
creased by soaking wheat seed in Cu EDTA solution for
12 h [6]. However, in that study there was also a signifi-
cant reduction in seedling emergence due to seed-soaked
Cu treatments in many cases, suggesting further investi-
gation to minimize damage to seedling emergence due to
seed-soaked Cu treatments. Earlier research has suggested
*Trade names in this publication are used only in the interest of accu-
rate reporting. No endorsement of a product to the exclusion of othe
r
similar products is implied by Agriculture and Agri-Food Canada or its
researchers.
that seedrow-placed Cu fertilizer can occasionally reduce
plant stand due to its toxic effect to germinating seed-

S. S. Malhi, D. Leach / Agricultural Sciences 3 (2012) 674-677 675
lings [7,8], depending on the soil moisture conditions
and time duration of seed-Cu fertilizer contact. We pos-
tulated that the amount of damage to germinating seed-
lings may be decreased by reducing the duration of
seed-Cu fertilizer solution contact time during seed
soaking. The objective of the present study was to deter-
mine the interaction effects of Cu rate (0, 15, 30, 60, 120
and 240 g·Cu·100 kg−1 wheat seed) and time duration (0,
4, 8 and 16 h) of seed-soaking in Cu EDTA fertilizer
solution on germination of wheat seeds incubated under
controlled temperature and humidity conditions.
2. MATERIALS AND METHODS
A laboratory incubation experiment (20˚C) was con-
ducted to find if the detrimental effects of seed-soaked
Cu on germination of wheat seeds can be minimized by
reducing time duration of seed in contact with Cu EDTA
fertilizer solution. There were 24 treatments arranged in
a 6 × 4 factorial design to include 6 amounts of Cu
EDTA solution (0, 15, 30, 60, 120 and 240 g·Cu·100 kg−1
wheat seed; equivalent to 0, 20, 40, 80, 160 and 320
g·Cu·ha−1) and 4 durations of seed-soaking time (0, 4, 8
and 16 h). In this experiment, the Cu source was Cu
EDTA liquid containing 93.5 g·Cu·L−1, which was pro-
vided by Tiger Industries, Calgary, Alberta, Canada. For
each seed-soaked Cu treatment, seed was soaked by
mixing 190 g of wheat seed in a 30 mL solution of Cu
EDTA liquid in distilled water in a covered small plastic
container, which was then left to soak for 0, 4, 8 or 16 h.
For the zero-Cu control treatment, wheat seed was
soaked in distilled water in the same way. For the non-
soaked seed treatments, the recommended rate of Cu
EDTA liquid was dissolved in 30 mL distilled water, and
the dry seeds were incubated with Cu EDTA solution, as
done in soaked treatments.
The data on percent seed germination were subjected
to analysis of variance (ANOVA) using GLM procedure
in SAS [9]. Main and interaction effects of Cu fertilizer
rates and seed-soaking time durations treatments were
determined. For each ANOVA, least significant differ-
ence at 5% probability (LSD0.05) and standard error of
the mean (SEM) were calculated, and LSD, SEM and
significance are reported. Linear and quadratic effects of
Cu rates for seed-soaked Cu EDTA solution treatments,
and selected contrasts between treatments are also re-
ported.
3. RESULTS AND DISCUSSION
The germination of wheat seed was 100% in the
zero-Cu control treatments, regardless of duration of
seed soaking time (Table 1). Compared to the zero-Cu
control, the percentage of seed germination decreased
considerably when seed was soaked in the Cu EDTA
fertilizer solution. However, the magnitude of reduc-
tion in seed germination due to Cu toxicity increased
with increasing duration of seed-soaking time in Cu
fertilizer solution. The seed germination decreased
substantially at the two higher Cu amounts in fertilizer
solution. For the seed-soaked treatments, the detri-
mental effect of Cu on seed germination was greatest
with 16 h soaking, where only 13% - 18% of the seeds
germinated with Cu applied at 15 to 30 g·Cu·100 kg−1
seed. For the 4 and 8 h seed soaking time treatments,
germination of wheat seed ranged from 73% to 83%
with 15 g·Cu·100 kg−1 seed treatment and 42% to 62%
with 30 g·Cu·100 kg−1 seed. For the seed-soaked Cu
EDTA solution treatments, the effects of Cu rates/
amounts in reducing seedling emergence were more
quadratic than linear (Figure 1). The R2-values were
usually much higher and more highly significant
Figure 1. Quadratic relationship showing percent germination of wheat seed at different amounts/rates of Cu in Cu EDTA fertilizer
olution as influenced by duration of seed-soaking time in an incubation experiment. s

S. S. Malhi, D. Leach / Agricultural Sciences 3 (2012) 674-677
676
Tabl e 1. Effect of Cu rate and duration of seed-soaking time of
wheat seed in Cu EDTA solution on percent germination in an
incubation experiment at controlled temperature of 20˚C.
Ttreatment Seed
germination (%)
Soaking time (h) Rate
(g·Cu·100 kg·seed−1)
Cu rate × soaking
time interaction
0 0 100
15 85
30 91
60 86
120 25
240 12
4 0 100
15 73
30 42
60 8
120 5
240 0
8 0 100
15 83
30 62
60 6
120 4
240 1
16 0 100
15 14
30 18
60 3
120 3
240 1
LSD0.05 9
SEM (significance) 3.3***
Cu rate mean 0 100
15 64
30 53
60 26
120 9
Continued
240 3
LSD0.05 5
SEM (significance) 1.6***
Soaking time
mean
0 66
4 38
8 42
16 23
LSD0.05 4
SEM (significance) 1.3***
Cu rate effects for each soaking time
(significance) R2 values
0
Linear 0.871**
Quadratic 0.904**
4 Linear 0.580*
Quadratic 0.905**
8 Linear 0.610*
Quadratic 0.920**
16 Linear 0.291ns
Quadratic 0.570ns
z, *, **, *** and ns refer to significant treatment effects in ANOVA at P ≤ 0.10,
P ≤ 0.05, P ≤ 0.01, P ≤ 0.001 and not significant, respectively.
for quadratic regressions than linear regressions, although
at 16 h soaking time both regressions were not signifi-
cant.
Earlier research with seedrow-placed Cu fertilizers has
occasionally shown reduction in plant density [8] which
was most likely due to toxic effect of Cu from the
seed-Cu contact in seedrow [7], depending on the soil
moisture conditions and time duration of seed-Cu fertil-
izer contact. In our previous recent field study where
wheat seed was soaked in Cu EDTA solution for 12 h, Cu
deficiency in wheat was prevented in the growing season
and seed yield increased considerably [6]. However, in
that study there was also a significant reduction in seed-
ling emergence due to seed-soaked Cu treatments in
many cases. Plant density was substantially below opti-
mum of 150 plants−2 in many seed-soaked Cu EDTA
solution treatments, especially at the two higher Cu rates.
This may have resulted in below optimum seed yield in
the seed-soaked Cu treatments, suggesting the need for
further investigation to minimize damage to seedling
emergence due to seed-soaked Cu treatments.

S. S. Malhi, D. Leach / Agricultural Sciences 3 (2012) 674-677 677
4. CONCLUSION
The detrimental effect of Cu on germination of wheat
seed soaked in Cu EDTA solution can be decreased by
reducing duration of soaking time from 16 h to 4 h or 8 h,
but this needs further investigation in soil under growth
chamber and/or field conditions before using this new
technology on a commercial scale.
5. ACKNOWLEDGEMENTS
The authors thank K. Strukoff for technical help.
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