Reducing toxic effect of seed-soaked Cu fertilizer on germination of wheat

doi:10.4236/as.2012.35082

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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: [email protected]

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

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

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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