Total soluble iron in the soil solution of physically, chemically and biologically different soils [Elektronische Ressource] / submitted by Tarek Ghassan Ammari

Informations

• Publié par: justus-liebig-universitat_giessen
• Publié le: 01 janvier 2005
• Nombre de lectures: 9
• Langue: English

Extrait

Institute of Plant Nutrition
Justus Liebig University Giessen / Germany
Prof. Dr. Drs. h. c. Konrad Mengel




Total Soluble Iron in the Soil Solution of
Physically, Chemically and Biologically Different
Soils



A thesis submitted for the requirement of the doctoral degree in agriculture
Department of Agriculture and Nutritional Sciences,
Home Economics and Environmental Management
Justus Liebig University Giessen / Germany



Submitted by
Tarek Ghassan Ammari
Amman / Jordan
2005


















































This Ph.D. work was approved by the defense committee
(Department 09: Agricultural and Nutritional Sciences,
Home Economics and Environmental Management) of
Justus Liebig University Giessen, as a thesis to award the
thDoctor Degree of Agricultural Science on October 17 2005.

Defense Committee:

Chairman: Prof. Dr. B. Honermeier.
1. Supervisor: Prof. Dr. K. Mengel.
2. Supervisor: Prof. Dr. W. Friedt.
1. Examiner: Prof. Dr. S. Schnell.
2. Examiner: Prof. Dr. H. Wegener. Content
1. Introduction…………………………………………………………………………..1
2. Materials and Methods………………………..…………………………………....8
2.1 General Description of the “Buchner Funnel Technique” (BFT)……………………..8
2.2 The Ferrozine-Hydroxylamine Hydrochloride Method……………………………....9
2.2.1 Reagents………………………………………………………………….....9
2.2.2 Procedure…………………………………………………………………..10
2.3 The Chemical and Physical Properties of the studied Soils………………………….11
2.4 The Determination of Total Soluble Fe in the Soil Solution and the
Fe Buffer Power of 32 Soils……………………………………………………………..12
2.5. The Influence of Microbial Activity on the Concentration
of the Total Soluble Fe in the Soil Solution……………………………………………...13
2.6. The Determination of the Percentage of the Organically-Complexed Fe…………...13
2.7. The Effect of Intercropping Swingle Citrumelo with Graminaceous
and Dicotyledonous Plant Species on its Fe Nutritional Status………………………….14
2.8 Statistical Analysis…………………………………………………………………...17
3. Results……………………………………………………………………………….18
3.1 Spectrophotometric determination of total soluble Fe in the soil
solution by the ferrozine-hydroxylamine hydrochloride method………………………..18
3.2 The determination of total soluble Fe concentration in the soil solution
and the Fe buffer power in 32 chemically and physically different soils………………..20
3.2.1 The concentration of total soluble Fe in the soil solutions………………...20
3.2.2 The relationship between total soluble Fe concentration in the
soil solution and soil chemical and physical properties………………………….21
3.2.3 The Fe buffer power of the 32 different soils……………………………...22
3.3 The chemical form of the soluble Fe in the soil solution of 30 different soils………25
3.4 The availability of soil Fe as influenced by microbial activity………………………27
3.5 The influence of intercropping swingle citrumelo with grass and dicot
plant species on its Fe nutritional status…………………………………………………31
4. Discussion…………………………………………………………………………..38
4.1 The Buchner Funnel Technique (BFT) and the ferrozine method…………………...38
4.1.1. The Buchner funnel technique…………………………………………….38
4.1.2 The ferrozine method………………………………………………………43
4.2 Total soluble Fe concentration in the soil solution and the Fe
buffer power of different soils…………………………………………………………...44
4.3 The central role of microbial activity in increasing the concentration
of total soluble Fe in the soil solution of different soils…………………………………68
4.4 The improvement of Fe nutrition of swingle citrumelo by intercropping
with perennial graminaceous and dicotyledonous plant species on a
calcareous soil……………………………………………………………………………97
5. Conclusions………………………………………………………………………..102
6. Zusammenfassung………………………………………………………………..104
7. References…………………………………………………………………………107
Acknowledgement…………………………………………………………………..118
Curriculum Vitae…………………………………………………………………….120







1 Introduction
1. Introduction:

Iron (Fe) is very insoluble in aerobic environments at neutral and alkaline
-39pH. The Fe(III) (hydr)oxides have solubility products ranging from 10 to
-44 -1710 , limiting the Fe(III) aqueous equilibrium concentration to ca. 10 M,
in the absence of complexing ligands (Hersman et al., 2001). Such
conditions are particularly prevalent in semiarid, calcareous soils estimated
to comprise over one-third of the world’s land surface area (Crowley et al.,
3+1987). Soluble Fe decreases 1000-fold for every unit increase in pH, and is
2+essentially unavailable above pH 4. Similarly, Fe decreases in solubility
3+ 2+100-fold for every unit increase in pH. In contrast to Fe , solubility of Fe
is also controlled by redox conditions, with the result that under reduced
2+conditions, above pH 4, Fe is potentially the most available form of soluble
inorganic Fe (Crowley et al., 1987). Lindsay and Schwab (1982) have
theoretically and experimentally determined that at neutral pH 7, pe+pH
2+must be below 9 to support the soluble Fe concentration critical for plant
growth. In calcareous, aerated soils, these reduced conditions would occur
only in oxygen-depleted microsites having high microbial activity, such as
around organic matter particles or possibly in the plant root rhizosphere
(Crowley et al., 1987).
-9 -4The critical value required for plant growth is between 10 and 10 M
Fe(III), a concentration that is two orders of magnitude higher than that
expected in aerated soil solutions at equilibrium for the sum of all inorganic
3+hydrolysis species of Fe (Siebner-Freibach et al., 2003). In addition, most
-6microorganisms require micromolar (10 M) concentrations of Fe to support
growth. Thus, in aerobic environments, microorganisms are faced with a 2 Introduction
-17discrepancy of ~10 orders of magnitude between available Fe (~10 M) and
their metabolic requirement for Fe (Hersman et al., 2000).
The low solubility of inorganic Fe in neutral and alkaline soils has
stimulated the search for the natural mechanisms by which Fe is made
available to higher plants. Soil chemists have implicated natural organic
chelates in the mobilization of Fe in soils (Powell and Szaniszlo, 1982). Iron
concentration in soil solution is often higher than that expected from
chemical equilibria equations of soil Fe minerals. This enhancement is
partially ascribed to the presence of organic molecules exhibiting various
extents of Fe-chelation abilities (Siebner-Freibach et al., 2004). The mobile
forms of Fe, whose concentration in the soil solution may be between 1 and
10 µM, may be utilized provided the root can separate the Fe from the ligand
at or very close to the site of uptake (Uren, 1984). Under conditions of Fe
limitation, O’Connor et al. (1971) stated that at neutral to basic soil pH,
inorganic Fe levels available for transport to the plant roots by both mass
flow and diffusion are below plant requirements. It appears, therefore, that
for plants growing in such soils, formation of soluble organic chelates is
important in supplying Fe. These compounds include root exudates, natural
chelators originated from the degradation of soil organic matter, metabolic
products of microorganisms, or Fe chelate fertilizer added to the soil
(Jurkevitch et al., 1988). Moreover, soil microbial activity may influence the
growth of higher plants by various processes such as mineralization of
organic N and S compounds, nitrification and sulfurication and also by the
microbial production of chelates which solubilize Fe (Rroco et al., 2003).
Among the most important of naturally-occurring, biosynthetic chelates are
the great number and variety of siderophores produced by microbes and the 3 Introduction
relatively few phytosiderophores produced by “Fe-efficient” grasses
(Crowley et al., 1991).
Studies of Crowley et al. (1988, 1991) have shown that the production of
chelating compounds by microorganisms increases Fe solubility in the
rhizosphere and hence increase plant Fe acquisition. Bacterial and fungal
siderophores and other chelating metabolites are assumed to serve as major
sources of plant-available Fe in the rhizosphere (Masalha et al., 2000).
Numerous prior studies have shown that a variety of microbial siderophores
provide Fe to both graminaceous and dicotyledonous plants, including
ferrichrome A for duckweed and tomato, ferrioxamine B (FOB) for
cucumber (Powell and Szaniszlo, 1982), FOB or rhodotorulic acid (RA) for
oat, tomato, sorghum, and sunflower, ferrichromes for oat, agrobactin for
bean and pea, and pseudobactin for peanut, cotton and sorghum (Wang et
al., 1993). Fe-rhizoferrin of Rhizopus arrhizus was found to be as effective
as FeEDDHA for the remedy of chlorosis in tomato and provided Fe for
barley and corn by ligand exchang