Introduction
In 2014, the Ministry of
Environmental Protection and the Ministry of Land and Resources issued The
National Soil Pollution Survey Public Notice, which pointed out that the
environmental quality of cultivated land is worrying, the rate of exceeding the
standard of cultivated land is 19.4%, and the main pollutants are cadmium,
nickel, copper, arsenic, mercury, lead, DDT and polycyclic aromatic hydroxyl.
Therefore, the remediation of heavy metals in soil has always been one of the
key issues of concern. At present, the remediation of heavy metal pollution at
home and abroad is mainly from physical repair, chemical remediation,
phytoremediation, leaching and electric remediation, etc. (Ding et al. 2012). Phytoremediation, as a kind
of low economic cost, low labor cost, high processing efficiency, no secondary
pollution, can recover heavy metal. Thus, it becomes a promising soil
restoration method for heavy metal pollution. However, the super-enriched
plants often used in phytoremediation are often small biomass, slow growth, and
the repair effect is not ideal (Wei et al. 2004;
Huang et al. 2006). In recent years, some scholars have used high biomass crops
as remediation plants (Kimenyu et al. 2009). The enrichment effect of maize
on Cd and Pb reached the standard of super-enriched plants. maize,
as an enriched plant, is rich in seed resources, widely published and large in
biomass. At the same time, potassium is one of the three elements of fertilizer
(Yuan et al. 2016). Application of potassium fertilizer can improve the
tolerance of Chinese cabbage to high cadmium stress, and potassium fertilizer
has application potential in the production of Chinese cabbage in cadmium
contaminated soil (Wang et al. 2012). The application of K2SO4
could reduce the absorption of Cd by oil and wheat vegetables in contaminated
soil. Obviously, fertilizer can improve the soil Rhizosphere environment, thus
affecting the chemical behavior of heavy metals in soil, resulting in the
difference of the availability of heavy metals, and then affecting the
absorption of heavy metals by plants (Jiao et al. 2011; Li et
al. 2014). However, most of the studies are mainly aimed at single heavy metal
pollution, but the research on farmland compound pollution is less. Therefore,
this paper adopts pot experiment to study the effect of different potassium
application concentrations on the absorption and enrichment of heavy metal Pb,
Cd, As and Cu on heavy metal soil by using maize as
the test material. Besides, the feasibility of the application of potassium
fertilizer to the improvement of the heavy metal-contaminated soil in maize was
discussed. The aim of this paper is to provide a reference for the good
combination of the fertilizer and the plant to repair the heavy metal
pollution.
Materials and Methods
Experimental details and
treatments
Experimental material: The tested soil, yellow brown
soil, was collected from the soil contaminated by heavy metals around a mining
area in Gejiu City, Yunnan Province. Five-point sampling method was used to
collect 0–20 cm soil samples from cultivated layer. After air drying, grinding
and 5 mm screening, the samples were used for pot experiment of maize culture.
The physical and chemical properties of the soil were pH 6.5, total nitrogen 8
g/kg, total phosphorus 5.018 g/kg, total potassium 3.7 g/kg, As
was 31.8 mg/kg, Cd was 11.3 mg/kg, Pb was 8.58 mg/kg, and Cu was 74.9 mg/kg.
The developed self-intersection breed Hongdan 3 was selected for several
generations by Institute of Agricultural Sciences in Honghe State. Test
reagent: KCl is potassium fertilizer, urea is nitrogen fertilizer, Na2HPO4 is
phosphorus fertilizer, all reagents are analytical pure.
Treatments: The plastic
flowerpot (inner
diameter 20 cm, high 18 cm) was used in a simulated pot experiment, and the
soil content in each pot was 2 kg. As base fertilize, the amount of urea was
200 mg/kg, and the amount of Na2HPO4 was 100 mg/kg. KCI
was added with the preset dosage. Six treatments were designed as follows:
Treatment 1: No potassium (short for CK); Treatment 2: application of KCI 100 mg/kg
(K1); treatment 3: application of KCI 200 mg/kg (K2); treatment 4: application
of KCI 300 mg/kg (K3); treatment 5: application of KCI 400 mg/kg (K4);
treatment 6: application of KCI 500 mg/kg (K5). There were 3 repeats for each
treatment. 10 seeds were sown in each pot, and after 2 weeks, 5 plants with
uniform growth were retained and cultured in a unified way. The growth indexes
of maize (plant height, leaf number, leaf length, leaf width, etc.) were observed every 3 days. After
2 months, the above ground part, underground part and soil samples were
collected respectively.
Determination of plant and
soil samples: The corn samples
were cleared and then removed at 105℃ for 15 min Table
1: Correlations of main carbohydrate metabolism
physiological indicators in tree peony leaves
|
Related Index |
|
Correlation coefficient |
||||
|
Sucrose |
Starch |
Hexose |
Sucrose/starch |
Hexose/sucrose |
||
|
Pn |
CK |
0.386 |
0.441 |
0.976* |
-0.415 |
0.881** |
|
RR |
0.843* |
0.792* |
0.948* |
0.607 |
0.130 |
|
|
AI |
CK |
0.296 |
0.479 |
0.764 |
-0.604 |
0.709 |
|
RR |
0.724 |
0.490 |
0.744 |
0.810* |
-0.107 |
|
|
SPS |
CK |
0.131 |
0.283 |
0.761 |
-0.319 |
0.764* |
|
RR |
0.787* |
0.778* |
0.674 |
0.511 |
-0.570 |
|
*, **Correlation is significant at the 0.05 level and 0.01 level
(2-tailed), respectively
%20391-397_files/image002.png)
Fig.
9: Effects of root restriction on the SPS
activity of tree peony leaves
%20391-397_files/image004.png)
Fig.
10:
Effects of root restriction on the SS activity of tree peony leaves
and dried at 70℃. The corn samples were smashed
with smashing machine powder and put into sealed bags. The soil was collected,
air-dried, grounded, over 100 mesh screen, into a sealed bag to match. The
contents of As, Cd, Pb and Cu in soil and plant samples were determined by
microwave digestion-ICP, effective As was extracted by NaH2PO4
method (Bao 2000), and effective Cd, Pb and Cu
were extracted by diethyltriamine pentaacetic acid-triethanolamine method (Sparrow
1996).
Data analysis
Microsoft Excel was used for
data processing and mapping, and SPSS 13.0 for variance analysis and
correlation analysis.
Results
Effect of potassium fertilizer
on maize growth
As can be seen from Table 1,
after the application of potassium fertilize to the maize seedlings, the
height, the width and the root length were higher than CK, but the leaf length
was lower than CK, and the effect of each treatment was different. In terms of
the effect on plant height of maize, the highest potassium application rate was
33. 3 cm for 500 mg/kg, followed by 200 and 300 mg/kg.
Through the analysis of variance, there was no significant difference among the
potassium treatments. In terms of leaf length, all treatments were lower than
CK, among them, 500 mg/kg treatment was best at 19.7 cm. However, there was no
significant difference between potassium application treatment and CK. In terms
of leaf width, the potassium application treatment of 100, 200 Table
1: Correlations of main carbohydrate metabolism
physiological indicators in tree peony leaves
|
Related Index |
|
Correlation coefficient |
||||
|
Sucrose |
Starch |
Hexose |
Sucrose/starch |
Hexose/sucrose |
||
|
Pn |
CK |
0.386 |
0.441 |
0.976* |
-0.415 |
0.881** |
|
RR |
0.843* |
0.792* |
0.948* |
0.607 |
0.130 |
|
|
AI |
CK |
0.296 |
0.479 |
0.764 |
-0.604 |
0.709 |
|
RR |
0.724 |
0.490 |
0.744 |
0.810* |
-0.107 |
|
|
SPS |
CK |
0.131 |
0.283 |
0.761 |
-0.319 |
0.764* |
|
RR |
0.787* |
0.778* |
0.674 |
0.511 |
-0.570 |
|
*, **Correlation is significant at the 0.05 level and 0.01 level
(2-tailed), respectively
%20391-397_files/image005.png)
Fig.
9: Effects of root restriction on the SPS
activity of tree peony leaves
%20391-397_files/image006.png)
Fig.
10:
Effects of root restriction on the SS activity of tree peony leaves
and 300 mg/kg were the best,
followed by 500 mg/kg, and there was no significant difference between each
fertilizer treatment and CK. In terms of root length, the highest amount of
potassium application was 25.9 cm in 200 mg/kg, followed by 300 mg/kg. However,
there was no significant difference between potassium application treatment and
CK. Overall, the potassium application amount of 200 mg/kg is better for maize
seedling growth.
Effects of potassium
fertilizer on absorption of heavy metals As, Cd, Pb and Cu in ground and
underground parts of maize
The effect on As: As can be seen from Fig. 1, as
the concentration of potassium is increased, the content of As in the upper
part of the maize is increased first, then decreased, then increased. Each
fertilizer treatment was significantly higher than CK (P < 0.05). Overall, it is 1.7–2.4 times higher than CK. However,
the performance of each treatment was different, and the content of As in the ground part of maize was the highest in the
treatment of 200 mg/kg application, followed by 300 and 100 mg/kg, the lowest
were 500 and 400 mg/kg. The results showed that potassium application could
significantly promote the absorption of As by maize
under the treatment of low concentration and medium concentration. For the
underground part, the As content of each potassium
treatment was lower than that of CK, the decreased rate was 38.6–42.9%, which
was significantly different from that of CK. However, there was no significant
difference among the fertilizer treatments. The content of As
in underground part of maize treated with 300 mg/kg was the highest. On the
whole, the content of As in maize was higher in the
above ground part than in the underground part.
The effect on Cd
It can be seen from Fig. 2
that different potassium concentration treatments can improve the absorption of
Cd by the ground and underground parts of maize. All treatments were
significantly higher than CK (P <
0.05). The ground part and underground parts increased 1.6–2.8 times and 1.8–1.9
times, respectively. With the increase of potassium concentration, the content
of Cd in ground part and underground part of maize increased at first and then
decreased. But the performance of each treatment is different. The ground part
shows that the highest content of Cd in maize treated with 300 mg/kg was 3.2 mg/kg,
which was significantly different from other potassium treatments (P < 0.05). The content of Cd in
underground part of maize treated with potassium was between 2.113–2.233 mg/kg.
Among them, 200 mg/kg treatment is the highest. The variance analysis showed
that there was no significant difference among the potassium treatments. On the
whole, except for 100 mg/kg treatment, the content of Cd in the ground part was
higher than that in the underground part, and the medium concentration potassium
application rate was beneficial to the absorption of heavy metal Cd by maize.
The effect on Pb
The application of potassium
fertilizer had a certain effect on the absorption of Pb
by maize plants. It can be seen from Fig. 3 that the content of Pb in ground
part of maize is significantly higher than that of CK (P < 0.05) which increased 1.7–2.3 times than CK. With the
increase of potassium concentration, the content of Pb
in maize increased at first, then decreased and then increased. Among them, 200
mg/kg treatment is the highest. The variance analysis showed that there was no
significant difference between each potassium fertilizer treatment. As for the
ground part, the content of Pb is lower than that of CK except for 500 mg/kg
treatment. With the increase of potassium application concentration, it
decreased at first and then increased; 500 mg/kg treatment was the highest up
to 2.247 mg/kg. After variance analysis, there was no significant difference
between 500 mg/kg treatment and CK, 100 and 200 mg/kg treatment, which holds
significant difference with 300 and 400 mg/kg. On the whole, the content of Pb
in the ground part of maize was higher than that in the underground part, and
the amount of potassium applied in the middle concentration was beneficial to
the absorption of heavy metal Pb by maize.
The effect on Cu
As can be seen from Fig. 4,
the application of potassium fertilizer can promote the absorption of Cu by the
ground and underground parts of maize. But the performance of each treatment is
different. With the increase of potassium application concentration, the
content of Cu in the ground part increased at first and then decreased and then
increased. The content of Cu in maize with different potassium treatment was
1.7–2.3 times higher than that of CK. Among them, 200 mg/kg treatment is the
highest, 300 mg/kg treatment is the second, 100 mg/kg
is the third. Through
variance analysis, there was no significant difference among the three treatments. With the
increase of potassium application, the content of Cu in underground part
decreased at first and then increased and then decreased, and the highest
treatment was 100 mg/kg up to 17.84 mg/kg. The results show that the absorption
of Cu in polluted soil can be promoted in the underground part of maize. On the
whole, except for 200 and 300 mg/kg treatment, the Cu content in the ground
part of the other treatments was lower than that in the underground part. Low
and medium concentration potassium Application is beneficial to the absorption
of heavy metal Cu in maize. This may be due to the high concentration of
potassium fertilizer and the increase of chloride ion, which leads to the
increase of charge in soil to increase the binding power of Cu ion.
%20391-397_files/image008.png)
Fig. 3: Effects
of potassium fertilizer on absorption of heavy metal pb in above-ground and underground parts of maize
%20391-397_files/image010.png)
Fig. 4: Effects
of potassium fertilizer on absorption of heavy metal Cu on above-ground and
underground parts of maize
Effects of potassium
fertilizer on available As, Cd, Pb and Cu in soil
Table 2 shows that potassium
fertilizer, compared with CK, can reduce the content of available As, Cd and Cu
in soil. However, the effects of different potassium application rates are
different. The content of effective As was decreased
12.2–28.8% than that of CK. The lowest amount of potassium application was 300 mg/kg,
which was significant different with CK, while there is no significant
difference with other potassium treatments. The content of effective Cd
decreased by 5.6–14.4%, and the potassium treatment with 500 mg/kg decreased
the most. Through
variance analysis, there was no significant difference between it and other treatments.
Compared with CK, the content of available Pb increased except potassium 500 mg/kg
treatment. Among them, the amount of potassium applied is up to twice as much
as that of 100 mg/kg treatment. By variance analysis, there was significant
difference. The content of available Cu decreased by 5.7–7.9%, and the
potassium application with 500 mg/kg was the least, but there was no
significant difference between the treatments.
Effect of potassium fertilizer
on transfer coefficient and enrichment coefficient of heavy metals
In order to further understand
the effect of potassium fertilizer on the transfer ability of As, Cd, Pb and Cu
absorbed by maize, the transfer coefficient (BTC) and enrichment coefficient
(BAC) of maize were calculated. As can be seen from Table 3, compared with CK,
the transfer coefficient of As in each potassium application treatment
increased by 3.03–4.00 times. 200 mg/kg treatment was the highest, 100 mg/kg
was the second, and 300 mg/kg was the third. Except for 100 mg/kg treatment,
the other treatments showed an increasing trend. The increased rate was 8.30–47.6%,
with 300 mg/kg treatment increased most. The transfer
coefficient of Pb increased by 1.85–3.11 times, with
300 mg/kg treatment up to the most. The transfer coefficient of Cu in
high concentration potassium application is lower than that of CK. Medium and
low concentration potassium application is higher than CK. 200 mg/kg treatment
was the highest, which increased by 31.1% than CK. On the whole, the medium
concentration of potassium application was beneficial to the transfer of heavy
metals As, Cd, Pb and Cu in maize. From the point of view of
the transfer ability of heavy metals, Pb > As > Cd > Cu.
As seen from the enrichment factor, the enrichment ratio of maize to As increased by 6.70–38.2%, up to 300 mg/ kg. Compared with
CK, the increase value of Cd enrichment coefficient in maize was 1.72–2.37
times, and the highest in 300 mg/kg treatment. The enrichment factor of Pb increased by 35.9–74.5% than CK, and it was treated with
the highest concentration of 200 mg/kg. Compared with CK, the increase of the
enrichment coefficient of Cu was 1.95–2.23 times, and the highest was treated
with 100 mg/kg. Therefore, the medium concentration of potassium application is
beneficial to the enrichment of As, Cd and Pb in maize
and the low concentration is beneficial to the enrichment of Cu, from the point
of view of the enrichment ability of heavy metals in maize, As > Pb > Cu > Cd.
Correlation between the amount
of potassium and the absorption of As, Cd, Pb and Cu in maize
As can be seen in Table 4, there is a certain correlation between the
potassium application amount, the heavy metal transfer coefficient and the
enrichment factor. Among them, except for the negative correlation between potassium Table 2: Effects of potassium fertilizer on
available As, Cd, Pb and Cu in soil (mg/soil kg)
|
|
As |
Cd |
Pb |
Cu |
|
CK |
4.128 ± 0.351a |
1.234 ± 0.118a |
1.035 ± 0.015b |
7.976 ± 0.728a |
|
K1 |
3.266 ± 0.910b |
1.139 ± 0.074a |
2.070 ± 0.792a |
7.440 ± 0.108a |
|
K2 |
3.625 ± 0.083ab |
1.165 ± 0.121a |
1.860 ± 0.667a |
7.516 ± 0.109a |
|
K3 |
2.940 ± 0.071b |
1.073 ± 0.021a |
1.506 ± 0.754ab |
7.351 ± 0.026a |
|
K4 |
3.135 ± 0.269b |
1.145 ± 0.033a |
1.253 ± 0.424b |
7.389 ± 0.184a |
|
K5 |
3.333 ± 0.205ab |
1.056 ± 0.062a |
0.862 ± 0.125bc |
7.339 ± 0.047a |
Table 3: Effect of potassium
fertilizer on transfer coefficient and enrichment coefficient of heavy metals
|
Treatment |
BTC |
BAC |
||||||
|
As |
Cd |
Pb |
Cu |
As |
Cd |
Pb |
Cu |
|
|
CK |
0.7456 |
0.9686 |
1.434 |
0.8784 |
0.5521 |
0.1998 |
0.5708 |
0.2076 |
|
K1 |
2.977 |
0.8414 |
3.628 |
0.9423 |
0.7431 |
0.3444 |
0.9089 |
0.4628 |
|
K2 |
2.986 |
1.069 |
4.212 |
1.152 |
0.7631 |
0.4090 |
0.9963 |
0.4295 |
|
K3 |
2.874 |
1.476 |
4.467 |
1.139 |
0.7523 |
0.4749 |
0.8947 |
0.4284 |
|
K4 |
2.266 |
1.047 |
3.310 |
0.7066 |
0.5891 |
0.3843 |
0.7761 |
0.4045 |
|
K5 |
2.605 |
1.054 |
2.659 |
0.8781 |
0.6636 |
0.3869 |
0.9585 |
0.4192 |
Table 4: Correlation between the amount
of potassium and the absorption of As, Cd, Pb and Cu
in Maize
|
|
BTC |
BAC |
|||||||
|
As |
Cd |
Pb |
Cu |
As |
Cd |
Pb |
Cu |
||
|
|
Amount of applied K |
0.438 |
0.364 |
0.261 |
-0.225 |
0.050 |
0.649 |
0.492 |
0.510 |
|
BTC BAC |
As |
- |
0.248 |
0.884* |
0.462 |
0.873* |
0.860* |
0.945** |
0.980** |
|
Cd |
- |
- |
0.504 |
0.506 |
0.314 |
0.663 |
0.198 |
0.169 |
|
|
Pb |
- |
- |
- |
0.610 |
0.852* |
0.889* |
0.754 |
0.830* |
|
|
Cu |
- |
- |
- |
- |
0.807 |
0.449 |
0.507 |
0.280 |
|
|
As |
- |
- |
- |
- |
- |
0.703 |
0.845* |
0.771 |
|
|
|
Cd |
- |
- |
- |
- |
- |
- |
0.793 |
0.833* |
|
|
Pb |
- |
- |
- |
- |
- |
- |
- |
0.898* |
application and Cu transfer coefficient (r = -0.226), there was a positive correlation
among the other treatments. The transfer coefficient of As and the transfer
coefficient of Pb (r = 0.884*), the transfer
coefficient of As and the enrichment factor of As (r = 0.873*), the transfer coefficient of As and
the enrichment factor of Cd (r = 0.860*), the transfer coefficient of Pb and
the enrichment factor of As (r = 0.852*), the transfer coefficient of Pb and
the enrichment factor of Cd (r = 0.889*), the transfer coefficient of Pb and
the enrichment factor of Cu (r = 0.830*), the transfer coefficient of As and
the enrichment factor of Pb (r = 0.845*), the enrichment factor of Cd and
the enrichment factor of Cu (r = 0.833*), the enrichment factor of Pb and the
enrichment factor of Cu (r = 0.898*), all of them showed
significant correlation (P <
0.05). The transfer coefficient of As and the enrichment
factor of Pb (r = 0.975**), the transfer coefficient of As and
the enrichment factor of Cu (r = 0.975**), achieved a very significant
correlation (P <
0.01).
Discussion
Potassium, as one of the necessary
nutritional elements for maize growth, plays an important role in maize growth
and nutrient absorption and accumulation. The potassium element can maintain
the high yield of the crop by promoting the synthesis of the protein and
increasing the stress resistance of the plant (Wang et al. 2012; Li et
al. 2014). This study shows that, potassium fertilizer can promote maize production,
and the effect of medium concentration (200 mg/kg) is better. This is
consistent on the effect of N, P, K fertilizer on
the absorption and accumulation of heavy metals in maize seedlings (Jiao et
al. 2011). However, there was no significant difference with the treatment
without potassium fertilizer. This may be due to the fact that potassium
fertilizer mainly improves the quality of crops, and the effect of potassium
fertilizer on plant yield is generally not as obvious as that of nitrogen
fertilizer.
Considering that potassium can maintain the osmotic pressure inside and
outside plants (Sparrow 1996; Chen et al.
2010). It may
reduce the effect of heavy metal stress on plant growth. The results showed
that different potassium application rates could not significantly promote the
growth of maize. However, it could significantly (P < 0.05) increase the content of As, Cd, Pb and Cu in the
ground part of maize, thus increasing the absorption of heavy metals in the
ground part of the soil polluted by heavy metals. Among them, low and medium
concentration treatment (100–300 mg/kg) was beneficial to maize. With the
increase of potassium application rate, the absorption capacity of As, Cd, Pb
and Cu in the ground part of maize increased at first and then decreased. This is consistent with the reesult that low concentration potassium
application is beneficial to maize absorption of Pb.
The trend of water-soluble heavy metals through plants also showed that with
the increase of potassium concentration, the absorption capacity of Pb in each
part of maize increased at first and then decreased. The main organ of plants
absorbing heavy metals in soil is root (Li et al. 2009; Jiao et al. 2011; Huo
et al. 2018). The order of heavy metal absorption in different parts of maize was root
> stem > leaf, which was not consistent with the result of this
study-stem and leaf > root, but it was consistent (Shi et
al. 2017; Guo et al. 2018). On sulfur chrysanthemum, Persian chrysanthemum and
wheat this may be due to the different crops and varieties tested the type and
amount of fertilizer applied the type of soil, the environmental conditions and
the selected growth period. Therefore, the application of potassium fertilizer
for the release and transfer of heavy metals in maize needs to be further
verified.
The toxicity of heavy metals is related not only to the total amount, but
also to the chemical form (Wahid and Ghani 2008).
Therefore, it is significant to understand the changes of different forms of
heavy metals in soil after fertilizer application. It was found that the
application of potassium fertilizer could promote the reduction of the content
of available heavy metals in soil to a certain extent. Among them, the contents
of available As, Cd and Cu in soil treated with medium and high concentration
potassium application were the least. This may be due to the fact that
fertilizers promote crop growth and increase the absorption of available heavy
metals by crops, thus reducing the content of heavy metals in the soil (Wang and Li 2014). This study showed that potassium
fertilizer could significantly increase the transfer ability and enrichment
coefficient of heavy metals As, Cd, Pb and Cu to the above ground part of maize.
Among them, the medium concentration potassium application level was beneficial
to the transfer of heavy metals As, Cd, Pb and Cu to maize, and the low and
middle concentration potassium application level was beneficial to the
enrichment of heavy metals As, Cd, Pb and Cu in maize. This is consistent with the reesult that Nitrogen fertilizer can
significantly enhance the enrichment coefficient of heavy metal Cd, Pb in maize and its transport capacity to shoot (Li et
al. 2014). In order to further understand the relationship between potassium
fertilizer and heavy metal absorption in maize, Pearson correlation analysis
was also carried out from the amount of potassium application, transfer
coefficient and enrichment coefficient. The results show that the transfer
ability and enrichment ability of potassium fertilizer to heavy metals As, Cd
and Pb are positively correlated. Therefore, potassium application amount is
also one of the factors affecting heavy metal absorption in maize. In addition,
the transfer coefficient and enrichment coefficient of some heavy metals
reached significant and extremely significant positive correlation, which may promote the absorption of heavy metals by maize.
Conclusion
In this study, pot
test method is adopted, and the corn is used as test material. In the soil contaminated by heavy
metal As-Cd-Pb-Cu, six different amounts of potassium fertilizer were used to
treat the soil, which are No potassium,
application of KCI 100 mg/kg, application of KCI 200 mg/kg, application of KCI 300
mg/kg, application of KCI 400 mg/kg, and application of KCI 500 mg/kg. It aims
to study the effects of different potassium concentrations on the
growth, absorption and accumulation of heavy metals (As, Cd, Pb and Cu) in corn
seedlings. The results can be
concluded as follows:
(1) In the compound polluted soil of the heavy metal
As-Cd-Pb-Cu, the medium concentration of potassium (200 and 300 mg/kg) can
promote the growth of corn, but there is no significant difference with CK.
(2) Potassium fertilizer can significantly increase the
absorption of heavy metals As, Cd, Pb and Cu in the aerial part of corn. The
treatment of low and medium concentration (100–300 mg/kg) is beneficial to the absorption of heavy
metals As, Cd, Pb and Cu. in the aerial part of corn. The effects of potassium
fertilizer on the absorption of heavy metals As, Cd, Pb and Cu in underground
part of corn are different. Potassium fertilizer can reduce the absorption of As and Pb in the underground part of corn, which can
significantly increase the content of Cd and Cu in the underground part, and
the middle and low concentration treatment is the best. Overall, the content of
heavy metals in the ground part is higher than that of the underground part.
(3) Potassium fertilizer could reduce the content of
available As, Cd and Cu in soil up to 28.8, 14.4 and 7.9%, respectively.
Medium and high concentration treatment is beneficial to reduce the content of
available As, Cd and Cu in soil. Potassium
fertilizer was beneficial to the increase of
available Pb content in soil, and 200 mg/kg increased the most.
(4) There was a positive correlation between potassium
application amount and some heavy metal transfer coefficients and enrichment
coefficients, but there was no significant correlation.
(5) Fertilizer is one of the important agricultural
measures to ensure the increase of agricultural yield and income. Besides, it
holds great effects on the adsorption and desorption of heavy metals in the
soil, the absorption of the heavy metals by the physical and chemical properties
and corps in the rhizosphere soil. The situation of heavy metal compound
pollution is more complex than that of single heavy metal element. The
mechanism of action is also very complex, but it turns out to be more
realistic. The determination of heavy metal content in plants can illustrate
the absorption ability of plants to heavy metals. This study finds that the application of low and medium
concentration potassium fertilizer is beneficial to the absorption of heavy
metals by maize However, it is
necessary to carry out further research on the influence of different potassium
fertilizer on the absorption of heavy metals on the corn on the composite
contaminated soil and its interaction with the nitrogen, the phosphate
fertilizer and its ions.
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