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Prediction of molybdenum availability to plants in differentiated soil conditions

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The aim of the study was to assess of plant available molybdenum (Mo) resources in the solutions of soils as well as to evaluate the effects of selected soil properties on changes of the Mo concentration in the soil solution. Sixty-two soil samples were investigated. The soil solutions were obtained by modified vacuum displacement method. The results showed that Mo concentrations in the soil solutions were much differentiated, ranging from 0.002 to approximately 0.100 µmol/L. Positive correlations were found between soil solution Mo concentration and soil pH as well as the contents of available phosphorous and organic carbon in soil. At the same time, Mo concentration was higher in the soil solutions obtained from soils with larger amounts of soil particles with diameter lesser than 0.02 mm. Among the analysed soil parameters in this study, soil pH is the most important factor that influences the Mo concentration in soil solution. Studies have shown that in acid sandy soils the amount of molybdenum found in the soil solution is too small to cover the nutritional requirements of the plants. This indicates the need of fertilization with this element. Regular liming of soils and fertilization with phosphorus can improve the availability of molybdenum to plants.
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Molybdenum (Mo) is an essential element for
proper growth and development of the major-
ity of living organisms, but it is required in very
small amounts and has a narrow range between
deficiency and toxicity. In plants, it plays a part in
nitrogen metabolism as a component of enzymes
such as nitrate reductase and nitrogenase. At the
same time, Mo participates in the metabolism of
sulphur, biosynthesis of plant hormones and ca-
tabolism of purine compounds (Kaiser et al. 2005).
Overall content of molybdenum in agricultural
soils ranges from 0.2 to 5.0 mg/kg (Scheffer and
Schachtschabel 2002). The plants take up Mo in
the form of the molybdate anions (MoO4
2– and
HMoO4
) which are the predominant species in
soil solution. A release of molybdenum from solid
mineral forms to soil solution is determined by
different soil properties, such as soil pH as well as
soil content of Fe, Mn, Al oxides, clay minerals and
organic carbon. Among these factors, soil pH has
the strongest effect on the processes of adsorbing
and releasing MnO4
2– ions into the soil solution.
The maximum adsorption of molybdenum onto
positively charged metal oxides occurs between
pH 4 and 5 (Riley et al. 1987, Xie et al. 1993, Gupta
1978, Xu et al. 2013). In acidic soils, molybdate
Prediction of molybdenum availability to plants
in differentiated soil conditions
B RUTKOWSKA1, W SZULC1,*, E SPYCHAJFABISIAK2, N PIOR3
1Agricultural Chemistry Department, Faculty of Agriculture and Biology,
Warsaw University of Life Sciences-SGGW, Warsaw, Poland
2Department of Agricultural Chemistry, Faculty of Agriculture and Biotechnology,
UTP University of Science and Technology, Bydgoszcz, Poland
3Institute of Intercultural Studies, Jagiellonian University in Krakow, Krakow, Poland
*Corresponding author: wieslaw_szulc@sggw.pl
ABSTRACT
Rutkowska B., Szulc W., Spychaj-Fabisiak E., Pior N. (2017): Prediction of molybdenum availability to plants
in differentiated soil conditions. Plant Soil Environ., 63: 491–497.
e aim of the study was to assess of plant available molybdenum (Mo) resources in the solutions of soils as well
as to evaluate the effects of selected soil properties on changes of the Mo concentration in the soil solution. Sixty-
two soil samples were investigated. e soil solutions were obtained by modified vacuum displacement method.
e results showed that Mo concentrations in the soil solutions were much differentiated, ranging from 0.002 to
approximately 0.100 µmol/L. Positive correlations were found between soil solution Mo concentration and soil pH
as well as the contents of available phosphorous and organic carbon in soil. At the same time, Mo concentration
was higher in the soil solutions obtained from soils with larger amounts of soil particles with diameter lesser than
0.02 mm. Among the analysed soil parameters in this study, soil pH is the most important factor that influences the
Mo concentration in soil solution. Studies have shown that in acid sandy soils the amount of molybdenum found
in the soil solution is too small to cover the nutritional requirements of the plants. is indicates the need of fertil-
ization with this element. Regular liming of soils and fertilization with phosphorus can improve the availability of
molybdenum to plants.
Keywords: micronutrient; mobility; leaching; solubility; acidic soils
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Plant Soil Environ. Vol. 63, 2017, No. 11: 491–497
doi: 10.17221/616/2017-PSE
anions are adsorbed onto positively charged Fe,
Mn and Al oxides as well as clay minerals and
organic colloids. Availability of molybdenum to
plants increases together with increasing soil pH.
For each unit of pH rise above 3, MoO4
2– solubility
increases about 100-fold, mainly through decreased
adsorption of metal oxides (Smith et al. 1997,
Jiang et al. 2015). The poorly drained wet soils,
rich in organic matter tend to accumulate MoO4
to high levels and from well-drained sandy soils
molybdenum is readily leached away (Riley et al.
1987). The availability of Mo to plants primarily
depends on the supply of soil available Mo and
is also related to the species of plant (McGrath
et al. 2010b).
The present study was undertaken with the aim
to (i) assess the amount of easily available re-
sources of molybdenum in the soil solutions of
agriculturally used soils; (ii) evaluate the effects
of some soil properties on changes of concentra-
tion of this element in the soil solution and (iii)
determine the degree of supply of selected crop
plants in Mo by the amount of this element that
is in the soil solution.
MATERIAL AND METHODS
Sixty-two soil samples were collected by the
Regional Agro-Chemical Laboratories from con-
trol points included in the system of the State
Environmental Monitoring. The control points
are located on arable land, characteristic for the
soil cover of the country. One control point cov-
ers an area of 650 km2. Depending on the area of
agricultural land, 2 to 6 soil samples were col-
lected from each voivodship. Soil samples were
taken as follows: GPS-determined point was the
central point of the square of 100 m2, from which
each individual sample was taken with a steel soil
probe from a depth of 0–30 cm. The combination
of individual samples was a collective sample rep-
resentative of the control point. Soil samples were
taken from the most common Polish soils: Haplic
Luvisols, Haplic Cambisols, Haplic Arenosols with
granulometric composition from loose sands to
heavy loams.
The soils were air-dried, and ground in an agate
mortar to pass through a 2.0 mm sieve for analysis.
Soil samples were characterized for: pH – by
the potentiometric method after extraction with
1 mol/L KCl (10 g of soil was suspended in 25 mL
of KCl and equilibrated for 24 h) using a pH meter
(apparatus: Schott, Mainz, Germany); available
P – by the Egner-Riehm (DL) method (Egner and
Riehm 1958); available Mo – after extraction in
1 mol/L HCl (10 g of soil was shaken with 100 mL
HCl on a rotary shaker for 2 h at 120 rounds per
min) by the inductively coupled plasma-atomic
emission spectrometry (ICP-AES, IRYS Advantage
ThermoElementar, Cambridge, UK); total Mo
by the aqua regia digestion, determined by the
ICP-AES; total organic carbon content – by dry
combustion at high temperatures in a furnace
with the collection and detection of evolved CO2
(Tiessen and Moir 1993); content of soil parti-
cles < 0.02 mm – by the laser diffraction method
(Ryżak et al. 2007). In Poland, the content of soil
particles < 0.02 mm determines the agricultural
usefulness of soil. On this basis, four categories
of soils are identified: very light (< 10% particles
< 0.02 mm), light (10–20%), medium (20–35%)
and heavy (> 35%).
The samples differed in terms of their physi-
co-chemical properties, such as: content of soil
particles < 0.02 mm, soil reaction, organic car-
bon content, available forms of molybdenum and
phosphorus in soil (Table 1).
The soil solutions of all the observed soils were
obtained by the modified vacuum displacement
Table 1. Properties of the investigated soils
Content of soil particles < 0.02 mm (%) < 10 (17) 10–20 (17) 20–35 (17) > 35
pHKCl < 4.5 (12) 4.6–5.5 (17) 5.6–6.5 (12) > 6.6 (21)
Available phosphorus content in soil (mg/kg) < 22 (7) 22–44 (15) 44–66 (12) > 66 (28)
Soil organic carbon content (g/kg) < 5 (3) 5–10 (30) 10–15 (25) > 15 (4)
Available molybdenum content in soil (mg/kg)* low (0.008–0.059) (42) medium (0.026–0.070) (20)
Total molybdenum content in soil (mg/kg) < 0.5 (21) 0.5–1.0 (32) 1.0–1.5 (7) > 1.5 (2)
*depending on soil pH and soil available phosphorus content in soil. Number of soils are in brackets
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method of Wolt and Graveel (1986). Air-dried soil
samples (100 g each) were wetted with redistilled
water to 100% field water capacity and then in-
cubated at room temperature for 72 h. Once the
balance between solid and liquid soil phases was
established, the soil solution was obtained with the
use of a vacuum pump (Dynavac OP4, Melbourne,
Australia) under pressure 0.08–0.09 MPa. The
obtained soil solutions were filtered through a
filter paper. The total concentration of Mo in
soil solutions was determined by the inductively
coupled plasma- atomic emission spectrometry
(ICP-AES).
The ICP-AES apparatus calibration was made
based on patterns prepared from the Single Element
Standards for ICP Solution by Ultra Scientific
company. To check the calibration curve, the solu-
tions were used to check the instrument and the
calibration (QC) at concentrations of 0.1 ppm
and 1 ppm – before the samples were studied, and
at every 20 samples according to the Combined
Quality Control Standard from Ultra Scientific
company.
Relationships between the concentration of Mo
in the soil solution and selected soil properties
were analysed with simple regression and corre-
lation at a significance level P = 0.05. Statistical
analyses were performed using the Statgraphics
Plus Professional software (StatPoint Technologies,
Inc., The Plains, Virginia, USA).
Relevant data on plant yields in Poland in the
year 2015 (Concise Statistical Yearbook of Poland
2016) and average molybdenum contents in plants
(Jadczyszyn 2000) were used in evaluating whether
molybdenum quantity in the soil solution was
sufficient for plant nutritional needs.
RESULTS AND DISCUSSION
The concentration of molybdenum in the
soil solutions analysed ranged from 0.002 to
0.100 mol/L and was differentiated depending
on soil properties. Soil solution Mo concentration
with range 0.005–0.035 mol/L was found in 66%
of all the analysed soils (Figure 1).
A similar range of Mo concentrations in the soil
solutions of Poland’s agricultural soils was earlier
observed by Rutkowska (1999). Wolt (1994) re-
ported that natural Mo concentration in the soil
solution observed in the USA and Great Britain
was 0.02 mol/L. On the other hand, Balík et al.
(2006) stated that Mo concentration in the soil
solutions of agriculturally used soils ranged from
0.006 to 0.06 mol/L.
Molybdenum concentration in the soil solutions
analysed was determined by the properties of the
observed soils. For strongly acidic (pH < 4.5) and
0
5
10
15
20
25
30
35
< 0.005 0.005
0.020
0.020–
0.035
0.035
0.050
0.050
0.065
> 0.065
Number of soils
Mo in soil solution (mmol/L)
Figure 1. Range of soil solution molybdenum (Mo)
concentration in agricultural soils in Poland
Minimum Maximum Mean Standard
deviation
Variation
coefficient
0.0021 0.091 0.027 0.022 81.48
Table 2. Average soil solution molybdenum (Mo) con-
centration according as soil physico-chemical proper-
ties (mol/L)
Content of soil particles < 0.02 mm (%)
< 10 10–20 20–35 > 35
Mo 0.018 0.039 0.041 0.047
pHKCl
< 4.5 4.6–5.5 5.6–6.5 > 6.6
Mo 0.009 0.014 0.037 0.072
available phosphorus content in soil (mg/kg)
< 22 22–44 44–66 > 66
Mo 0.011 0.015 0.017 0.048
soil organic carbon content (g/kg)
< 5 5–10 10–15 > 15
Mo 0.007 0.021 0.041 0.056
soil available Mo
low medium
Mo 0.023 0.045
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acidic soils (pH 4.6–5.5), Mo concentration in the
soil solution was lower than 0.02 mol/L. It was
significantly increased at rising soil pH values
and reached on average 0.072 mol/L in soils with
neutral and alkaline soil pH (pH > 6.6) (Table 2,
Figure 2a). In the soil solution of soils with pH
value higher than 5.0 MoO4
2– ions dominate. Above
pH 4.2, MoO4
is the common anion followed in
decreasing order by MoO4
> HMO4
> H2MO4
0 >
MoO2(OH)2
+ > MoO2
2+ (Lindsay 1979). In acidic
soils with pH 4–5, molybdate anions are strongly
adsorbed by positively charged oxides of Fe, Mn
and Al, and this holds back availability of Mo for
plants (Smith et al. 1997). With increasing soil pH
the concentration of MoO4
2– ions in the soil solu-
tion increases. As Lindsay (1979) and McGrath et
al. (2010a) reported, for each unit of the pH value
above 3.0, the concentration of molybdate ions can
increase even one hundred times. Enhancement
of Mo mobility in soil at high pH values is caused
by an increase of free negative charges on soil col-
loids, stronger competition between molybdates
and hydroxyl anions for adsorption sites, as well as
by lower activity of Al and Fe oxides, which is the
cause of reducing the amount of free positive sites
able to adsorb molybdenum (Jarrell and Dawson
1978, Jiang et al. 2015).
The content of soil particles also determined Mo
concentration in the soil solution. In heavy soils
(> 35% of soil fractions < 0.02 mm), soil solution
Mo concentration was more than two times higher
when compared with that in very light soils (< 10%
of soil fractions < 0.02 mm) (Table 2). Low Mo
concentration in the soil solution of very light
soils was connected with their strongly acidic soil
reaction. On the other hand, soils with more than
35% content of fractions with particle diameter
< 0.02 mm were characteristic of pH higher than
5.6. Studies of Jones and Belling (1967) showed
enhanced molybdenum leaching in well-aired sandy
soils. This process depends on soil pH. As indicated
by Riley et al. (1987), molybdenum leaching from
sandy soils with acidic soil reaction is limited be-
cause solubility of this element is restricted. The
concentration of Mo in soil solution increased
with the content of available molybdenum in soil
(Figure 2b). The results of this study showed that
with an increasing content of available phospho-
rous in soil the concentration of molybdenum in
the soil solution increased, which was proven by
y = 0.0002e0.7809x
r = 0.91**
0
0.02
0.04
0.06
0.08
0.1
3.5 5.5 7.5
Mo (mmol/L)
pH
y = 0.7301x + 0.0028
r = 0.68**
0
0.02
0.04
0.06
0.08
0.1
0 0.05
Mo (mg/kg)
y = 0.0004x + 0.0008
r = 0.85**
0
0.02
0.04
0.06
0.08
0.1
0 50 100150 200
Mo (mmol/L)
P (mg/kg)
y = 0.0042x – 0.011
r = 0.62**
0
0.02
0.04
0.06
0.08
0.1
0 5 10 15 20
Corg (g/kg)
Figure 2. Relationship between soil solution molybdenum (Mo) concentration and (a) soil pH; (b) available Mo;
(c) available phosphorus (P), and (d) organic carbon (Corg) content in soil. **P < 0.01
(a) (b)
(c) (d)
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correlation coefficient r = 0.85 (Figure 2c). Average
molybdenum concentration in the soil solution
depended on the content of available phospho-
rous in soil. In soils exceedingly rich in available
phosphorous (> 66 mg/kg) soil solution Mo con-
centration was four times higher when compared
with soils with low available phosphorous contents
(< 22 mg/kg). In soil, phosphates compete with
molybdates for adsorption sites on the surface of
the solid soil layer, and with increasing available
phosphorous amounts numerous adsorption sites
with high affinity for molybdenum can be blocked
by phosphates (Xie and MacKenzie 1991, Vistoso
et al. 2009). As a result of this process, desorp-
tion of MoO4
2– into the soil solution is enhanced.
The process does not depend on soil reaction and
is started in acidic soils. The soils tested were
of low content of organic carbon. Nevertheless,
significant relationships between soil solution Mo
concentration and soil organic carbon contents
were shown (Figure 2d).
In soils with organic carbon content > 15 g/kg,
soil solution Mo concentration was eight times
higher when compared with soils < 5 g/kg of or-
ganic carbon (Table 2). Studies on the effects
of organic matter on molybdenum mobility are
scarce and their results are not consistent. Kasimov
et al. (2011) showed that the humus content in
soil strongly affects molybdenum mobility. The
strength of Mo absorption increased with higher
humus in soil. Karimian and Cox (1978) and Xu
et al. (2013) indicated that the soil solution Mo
concentration decreased with increasing contents
of organic carbon in soil, most probably as a result
of formation of complexes with humic acids. On
the other hand, Jenne (1977) as well as Reddy et
al. (1997) showed that in the soil solution MoO4
2–
anions could form complex ions with metal cations
(K, Na, Ca, Mg) and also with humic and fulvic
acids. This influences indirectly the increase of
molybdenum availability for plants through re-
straint adsorption of ions MoO4
2– on Fe, Mn and
Al oxides, especially in acidic soils.
Based on the multiple regression analysis, the
relationship between the concentration of molyb-
denum in soil solution and the content of available
molybdenum, available phosphorus and organic
carbon in soil was significantly determined by
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0 0.02 0.04 0.06 0.08
Mo (µmol/L)
Mo (mg/kg)
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0 50 100 150 200
P (mg/kg)
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.1
0 5 10 15 20
Mo (µmol/L)
Corg (g/kg)
0
0,01
0,02
0,03
0,04
0,05
0,06
0,07
0,08
0 0,02 0,04 0,06 0,08
Mo (µmol/L)
Mo (mg/kg)
pH < 4.5 pH = 4.6–5.5
pH = 5.6–6.5 pH > 6.6
pH < 4.5 pH = 4.6–5.5
pH = 5.6–6.5 pH > 6.6
0
0,01
0,02
0,03
0,04
0,05
0,06
0,07
0,08
0,09
0 50 100 150 200
Mo (µmol/L)
P (mg/kg)
0
0,01
0,02
0,03
0,04
0,05
0,06
0,07
0,08
0,09
0,1
0 5 10 15 20
Mo (µmol/L)
Corg (g/kg)
pH = 5.6–6.5 pH > 6.6
Figure 3. Effect of soil pH on the relationship between
molybdenum (Mo) concentration in soil solution and
(a) available Mo; (b) available phosphorus (P) and (c)
organic carbon (Corg) content in soil
(a) (b)
(c)
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soil pH (Figure 3, Table 3). The concentration of
molybdenum in the soil solution of strongly acidic
soils was the smallest and significantly increased
with the increase in the amount of molybdenum
available in the soil. However, in soils with pH >
6.6, the concentration of molybdenum in the soil
solution was significantly higher. Under such condi-
tions, the increase in the amount of molybdenum
available in the soil caused a much higher increase
in the concentration of molybdenum in the soil
solution than in strongly acidic soils (Figure 3a).
Similar trends were found in the relationship be-
tween molybdenum concentration in soil solution
and phosphorus content in soil (Figure 3b) and
organic carbon content in soil (Figure 3c).
Average uptake of molybdenum by plants in
Polish agriculture ranged from 1.68 to about 10 g
per hectare (Table 4). The average content of ac-
tive molybdenum in the arable layer of soil is suf-
ficient to cover the nutritional needs only in the
case of rye. This corresponds to a concentration of
molybdenum in the soil solution at 0.027 µmol/L.
57% of the analysed soils are characterized by a
concentration less than sufficient to cover the
nutritional needs of plants (Figure 1).
The results of the study carried out indicate that
molybdenum concentrations in the soil solutions of
agriculturally used soils in Poland are very variable
and depend on physico-chemical soil properties.
A significant positive correlation was found be-
tween soil solution Mo concentration and soil pH,
available phosphorous contents in soil as well as
soil organic carbon contents. In the soil solution
of soils with pH > 6.6, the concentration of Mo
was eight times higher when compared with soils
with pH < 4.5. Also an eight-fold increase of soil
solution Mo concentration was observed under
the influence of increased soil organic carbon
contents from below 5 to more than 15 g/kg. At
the same time, the concentration of molybdenum
in the soil solutions increased in the observed soils
with increased both the content of soil particles
with the diameter lesser than 0.02 mm and the
quantity of molybdenum forms. Plants cultivated
Table 3. Regression equation between molybdenum (Mo) concentration in soil solution and selected soil properties
Dependent variable Independent variable Equation P R2 (%)
Mo soil solution (Moss)
Mo available (Moav) soil pH Moss = –0.06 + 0.51 Moav + 0.11 pH < 0.01 75.06
P available (Pav) soil pH Moss = –0.06 + 0.001 Pav + 0.14 pH < 0.01 56.23
Corg soil pH Moss = –0.06 + 0.002 Corg + 0.01 pH < 0.01 50.70
Table 4. Yield (t/ha) and molybdenum (Mo) uptake (g/ha) by selected plants and content of Mo in soil
Plant Yield Molybdenum uptake
minimum maximum average minimum maximum average
Winter wheat (Triticum aestivum)3.20 7.20 4.13 2.24 5.04 2.89
Rye (Secale cereale)2.30 5.80 2.40 1.61 4.06 1.68
Green forage corn (Zea mays)30.00 58.00 48.00 4.50 8.70 7.20
Winter rape (Brassica napus)2.20 4.00 2.24 2.20 4.00 2.66
Potato (Solanum tuberosum)12.00 45.00 23.20 1.32 4.95 2.55
Sugar beet (Beta vulgaris)15.00 69.00 57.40 2.55 11.73 9.76
Mo quantity in the solution of soil arable layer
Minimum maximum average minimum maximum average
(µmol/L) (g/ha)
0.0021 0.091 0.027 0.19 8.25 2.45
*according to the Concise Statistical Yearbook of Poland (2016) and Jadczyszyn (2000)
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in sandy, acidic soils may show deficiencies of Mo
due to the low molybdenum concentration in soil
solution as well as soil characteristics that limit its
availability to the plants. Regular liming of soils
and fertilization with phosphorus can improve the
availability of molybdenum to plants.
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... The increase in Mo levels in IC pea grains in Auzeville soil may stem from their heightened demand for N fixation, more pronounced in IC than in SC peas. Mo availability in soils is influenced by abiotic factors such as pH and humidity, with molybdate being the most accessible form at pH levels above 4.2 (Rutkowska et al. 2017;Tejada-Jiménez et al. 2009;Yang and Wang 2021), suggesting the Mo was likely more available in Auzeville than in Epoisses soil due to pH differences (Supplementary Table 1). ...
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Background and aims Cereal-legume intercropping (IC) is proposed to address the challenges of increasing yields and improving crop nutrient quality, crucial for food security and human health. This study aimed to characterize the impact of pea-wheat IC on grain ionome composition, and asses its potential relation with the abundance of Pseudomonas spp. and Enterobacterales in plant roots. Methods In a field experiment, four pea varieties were cultivated in sole- or intercropping with wheat in two different soil types. Grain ionome was analysed by mass spectrometry, while Pseudomonas spp. and Enterobacterales abundances were quantified by qPCR. Results Pea grains intercropped with wheat showed increased concentrations of Ca, Mg, and Mo in one soil type, and higher Mn and Ni concentrations and total grain content in another. Wheat grains intercropped with peas, exhibited increased Cu, Fe, Mn, N, S, and Zn concentrations and/or total grain content, only in one soil type. Pseudomonas spp. showed increased abundance in pea root tissues when intercropped with wheat, specifically in one soil type. Pseudomonas spp. appeared to affect K, Fe, and Zn concentrations or total content in pea grains, depending on the cropping system. Conclusion These findings suggest that IC can enhance specific element concentrations and/or total grain content in pea and wheat grains, upon soil type. Pseudomonas spp. may facilitate nutrient uptake and translocation to grains. Further research is needed to understand the mechanisms behind element accumulation in IC grains and to explore the potential benefits of IC for plant nutrition and growth.
... Mo bioavailability is controlled by sorption and desorption dynamics in soil. In our experiment, soil C content, DOC, pH, and Fe were related to Mo bioavailability: 4.3.1 Relationship between water soluble Mo, DOC, and total soil C In agreement with our results, previous studies have found a positive relationship between soil C content and the availability of Mo (Lombin, 1985;Marks et al., 2015;Rutkowska et al., 2017), indicating that water-soluble Mo originates from SOM mineralization and that high levels of water-soluble Mo are generally associated with a high content of OM. This is in accordance with the observation that high C soils had more water-soluble Relationship between water soluble Mo and reduction in net nitrification in (A) 16% C soil, (B) 11% C soil, (C) 3% C soil, (D) 1% C-CL soil, (E) 1%C-Sand soil and (F) across all soils amended with flocs. ...
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Nitrification converts ammonium (NH4+) to nitrate (NO3−) using metalloenzymes, the activity of which depends on iron (Fe), molybdenum (Mo), and copper (Cu) availability. Iron-organic carbon coprecipitates (or Fe-OC flocs) are key byproducts of wastewater treatment industry and natural components of soil that may affect nitrification by changing the bioavailability of these metals. Here, we used flocs of different chemistry (aromatic and aliphatic) and known Fe and C composition to investigate their effects on nitrification in soils along a soil C gradient. Both aromatic and aliphatic flocs reduced net nitrification, but the magnitude of their effect was more pronounced in soils with low C content as opposed to those with high C content. Within each soil, both flocs reduced net nitrification similarly. In the presence of flocs, the bioavailability of Mo (assessed by changes in the concentration of water-soluble Mo) was dramatically decreased in low C soils, possibly because Mo was incorporated into or adsorbed to flocs or their decomposition products. In contrast, Mo bioavailability in high C soils was decreased to a lesser extent by flocs, likely because organic matter limited floc adsorption capacity and released Mo through mineralization. The depletion of bioavailable Mo by flocs in agricultural soils has the potential to impede soil nitrification and extend the residence time of NH4+ and its availability to plants and microbes.
... Adsorption of B to Fe in acidic soils is often dominated by ferrihydrite due to its high specific surface area and small particle size (Brinza et al., 2019;van Eynde et al., 2020). Studies also showed that Fe can adsorb Mo in highly weathered and acidic soils dominated by oxides of Fe and Al, thereby, reducing their availability to plants (Brinza et al., 2019;Rutkowska et al., 2017;Xu et al., 2013). The tissue Mo concentration at the reproductive stage in Tifton, which has a top sandy layer, tended to be higher when MN was applied without SN (Table 4). ...
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Highly weathered soils have low native fertility; thus, optimum nutrient management is critical, especially for a high‐input crop such as corn (Zea mays). Field studies were established in Plains and Tifton, GA, to assess secondary nutrient (SN; Mg, Ca, and S) and micronutrient (MN; B, Zn, Mn, Fe, Cu, and Mo) application effects on corn fertilized with primary nutrients (PN; N, P, and K) to achieve 12.5 Mg ha⁻¹ (low) and 25.1 Mg ha⁻¹ (high) yields. Both Plains and Tifton have Ultisol soil. However, the Tifton soil has a 30‐cm top sandy layer, and the Plains soil has no top sandy layer. Differences in corn nutrient concentrations were observed at the V5–V7 stage but not in biomass accumulation. The 12.5 Mg ha⁻¹ target grain yield from applying the low PN was exceeded at both locations (by 19.0%–26.6% in Plains and 6.3%–19.7% in Tifton), irrespective of the SN or MN application. However, the 25.1 Mg ha⁻¹ target grain yield from applying the high PN rate was not achieved, with yields of 16.9–17.7 Mg ha⁻¹ in Plains and 15.7–17.1 Mg ha⁻¹ in Tifton obtained. The SN and/or MN application increased corn yield (by 2.3%–13.6%) across all conditions, but the differences were statistically significant under just the low PN rate in Tifton. Overall, the results showed that SN and MN could be yield‐limiting factors of corn in the Ultisol soils tested in the study, and also 12.5 Mg ha⁻¹ corn yield can be achieved with lower PN rates than currently recommended.
... The leaching of Mo was almost zero in the incubated soils (0.1 vs 0.0). The leaching of molybdenum from solid minerals to soil solution depends on e.g., soil pH, soil content of Fe, Mn, Al-oxides, clay minerals, and organic carbon (Rutkowska et al., 2017). The maximum adsorption of Mo onto positively charged metal oxides occurs between pH 4 and 5 (Xu et al., 2013). ...
... After liming, the increase in soil pH results in greater availability of Mo in the soil. According to Rutkowska et al. (2017), increasing the pH unit (i.e. from 4.5 to 5.5) can increase the molybdate solubility by up to a hundred times. Such inference may have contributed to the results obtained in this study, in which the requirement of plants in Mo may have been fully met with the soil reserve and had a low response to the foliar application of Mo. ...
... Therefore, the use of Plant Growth Promoting Organisms (PGPR) is a useful technique for improving crop productivity and food quality in a sustainable and environmentally friendly agricultural system [8][9][10][11][12]. Molybdenum is an essential micronutrient necessary for plant growth due to its importance in the processes of bioreduction of molecular nitrogen and protein synthesis in plants, and it affects the increase of plant biomass [13][14][15]. The soybean crop (Glycine max L.) is one of the world's summer leguminous crops grown for oil and protein [16], that are used in industry and food, as the percentage of protein in its seeds ranges between 30 and 50% and the oil is between 14 and 24 percent. ...
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With the aim of reducing chemical fertilizers and relying on environmentally friendly natural biofertilizers that promote plant growth and increase yield, especially in gypsiferous soils spread in arid and semi-arid regions, which suffer from physical, chemical, fertility, and biological problems, which in turn affect the density of microorganisms, This experiment was conducted to study the efficiency of the inoculum prepared from the bacteria E. cloacae and E. ludwigii isolated from gypsiferous soils and molecularly characterized in improving the growth and yield of soybeans under different levels of molybdenum in gypsiferous soil, possibly due to its absence, particularly the bacteria responsible for nitrogen fixation. The results showed that the two treatments inoculated with E. cloacae and E. ludiwgii were significantly superior to the uninoculated treatment in all studied growth and yield traits and the percentage of nitrogen and protein in the seeds, and that the treatment inoculated with E. cloacae bacteria was superior to the treatment inoculated with E. ludiwgii bacteria in all traits, as well as the treatment fertilized at the level of 2 kg Mo ha ⁻¹ was significantly superior to the non-fertilized in all traits and showed The results of the interaction between inoculation and fertilization with molybdenum showed that the E. cloacae + 2 kg Mo ha ⁻¹ treatment was superior to the comparison treatment in all traits and gave values of 278 pod plant ⁻¹ , 127.66 g plant ⁻¹ , 6.23 tons ha ⁻¹ , 6.27%, and 39.13%. 0.36%, 0.071% for the number of pods, weight of pods, grain yield, concentrations of nitrogen, protein, and molybdenum in the seeds, and the concentration of molybdenum remaining in the soil after harvest, respectively, compared to the comparison treatment that gave the values 150.67 pod plant ⁻¹ , 68.33 g plant ⁻¹ , 3.43 tons ha ⁻¹ , 5.42%, 33.83%, 0.33%, and 0.068 for the aforementioned characteristics, respectively.
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Particle size distribution affects many physical soil properties and processes taking place in soil. There are many methods to determine the particle size distribution. The most frequently used are the sieve, sieve-pipette and sedimentation methods. Technological progress in electronics permitted a wide use of new methods of particle size distribution measurement in soil, e.g. the laser diffraction method. A comparison of particle size distribution obtained with the universally used areometer method (Cassagrande, modified by Prószynski) with results from the laser diffraction method for soil material received from grey-brown podzolic soil is presented in this work. The largest differences between the results were obtained for the smallest fraction determined with the areometer and laser diffraction methods. In a majority of other cases the slopes of interpolated straight lines were contained within the range of 0.81 ÷ 1.09.
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The effect of N-S fertilizers on the molybdenum content in oilseed rape plants was investigated in precision field trials. Evaluation was carried out on unfertilized control and two treatments of single fertilizer rates in the first spring fertilizer application, using 100 kg N/ha in AN treatment (nitrochalk) and 100 kg N/ha + 50 kg S/ha in ANS treatment (ammonium nitrate and ammonium sulphate). The results confirmed the significance of sulphur fertilization for the winter oilseed rape plant's cultivation technology, even on fertile soils in the Czech Republic. The control treatment produced a yield of 3.7 t/ha, while in the AN treatment the yield was 49% higher, and the ANS treatment was 60% higher. An antagonistic relationship between the sulphate and molybdenum anions in their absorption by the plants was demonstrated. The molybdenum content in the flowering period of the plants was determined in mg/kg as follows - in the ANS treatment: 0.17 in root, 0.12 in stem, 1.56 in upper leaves, 0.90 in lower leaves, and 1.17 in the flower petals. Higher and statistically more significant molybdenum levels were determined in the AN treatment: 0.21 in the root, 0.19 in the stem, 2.40 in the upper leaves, 1.72 in the lower leaves, and 1.50 mg/kg in the flower petals. The total above-ground biomass of the plants in the flowering period had accumulated molybdenum at 6.06 g/ha in the ANS treatment, and 8.44 g/ha in the AN treatment.
Book
Deals with all aspects of chemistry involving the fluid element found in soils. Stresses the direct analysis and interpretation of soil solution composition in order to gain insights into chemical reactivity and availability in soils. Contains practical laboratory and field techniques for obtaining and analyzing soil solutions. Also provides theoretical background on the physical and analytical chemistry involved.
Chapter
Molybdenum (Mo) deficiencies in field-grown plants were first recorded more than 50 years ago and this book condenses all the information currently available on the subject of molybdenum as it relates to soils, crops and livestock. The book reviews our knowledge of the chemistry and mineralogy of Mo, the extraction of available Mo from various soils, the various analytical methods of determining Mo in soils and plants, the biochemical role of Mo in crop production, the technology and application of Mo fertilizers to crops, the response to Mo of various temperate and tropical crops, Mo deficiency and toxicity in various plant species, the interaction of Mo with other plant nutrients, and the distribution of Mo within the plant. Factors affecting the availability of soil Mo to plants and Mo status in the semi-arid and sub-humid tropics are also discussed.
Chapter
Molybdenum (Mo) deficiencies in field-grown plants were first recorded more than 50 years ago and this book condenses all the information currently available on the subject of molybdenum as it relates to soils, crops and livestock. The book reviews our knowledge of the chemistry and mineralogy of Mo, the extraction of available Mo from various soils, the various analytical methods of determining Mo in soils and plants, the biochemical role of Mo in crop production, the technology and application of Mo fertilizers to crops, the response to Mo of various temperate and tropical crops, Mo deficiency and toxicity in various plant species, the interaction of Mo with other plant nutrients, and the distribution of Mo within the plant. Factors affecting the availability of soil Mo to plants and Mo status in the semi-arid and sub-humid tropics are also discussed.
Chapter
Molybdenum (Mo) deficiencies in field-grown plants were first recorded more than 50 years ago and this book condenses all the information currently available on the subject of molybdenum as it relates to soils, crops and livestock. The book reviews our knowledge of the chemistry and mineralogy of Mo, the extraction of available Mo from various soils, the various analytical methods of determining Mo in soils and plants, the biochemical role of Mo in crop production, the technology and application of Mo fertilizers to crops, the response to Mo of various temperate and tropical crops, Mo deficiency and toxicity in various plant species, the interaction of Mo with other plant nutrients, and the distribution of Mo within the plant. Factors affecting the availability of soil Mo to plants and Mo status in the semi-arid and sub-humid tropics are also discussed.
Article
Purpose Molybdenum (Mo) is an essential element critical to biochemical processes in plants and animals. The effects of soil properties on the availability of Mo to rice were investigated. Materials and methods A total of 56 paired samples of topsoil and rice were collected. Relevant parameters in soil and Mo in rice grains were measured, and the results were analyzed using statistical methods. Results and discussion Descriptive statistics for Mo contents in soil and soil properties are presented. Mo adsorption can be predicted using the following soil chemical properties: pH, cation exchange capacity, soil organic carbon (SOC) content, inorganic carbon content, and iron oxide content. This study focused on soil pH, SOC, S, and Na 2 O because these parameters are the most important factors in controlling the levels of soil Mo in correlation analyses. SOC and available P were the best predictors of Mo availability. Conclusions Among the soil properties in this study, soil pH is the most important factor restricting the supply of soil available Mo. The dominant factors that directly affected Mo availability were the levels of available P and SOC. Leaching and adsorption of Mo in soils were considered key processes that affected the levels of soil available Mo. Rice grown in the study area may pose potential Mo risks to food safety and human health, especially in rural areas.