M. A. Khodshenas; J. Ghadbeiklou; M. Dadivar
Abstract
Introduction: Soil test has an important role in plant nutrition management to obtain the economical agriculture system. The nutrient concentration in soils that indicates the division between responsive and non-responsive conditions is termed the critical level. Before any fertilizer recommendation, ...
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Introduction: Soil test has an important role in plant nutrition management to obtain the economical agriculture system. The nutrient concentration in soils that indicates the division between responsive and non-responsive conditions is termed the critical level. Before any fertilizer recommendation, we should be aware of the amount of nutrient critical levels in each region. Soil test results in an area, is not applicable for other agricultural areas. Therefore, these tests should be carried out in the soils of a desired area, so that the soil test could be the base for fertilizer recommendation. Iron is an essential micro element in the soil that mainly was found as insoluble (Ferric or Fe3+) form. Solubility of total inorganic iron decreases between pH 7.4 to 8.5. Bean (Phaseolus vulgaris L.) crop is one of the most widely grown throughout the Markazi province in Iran and has high nutritional value for human. Knowing that bean is a sensitive plant to iron, and because of lack of any information about iron critical level and regional calibration, this study was conducted in Markazi province.
Materials and Methods: Eighteen soil surface samples (0-30 cm) selected with a wide range of soil properties and iron concentration (extracted with DTPA method) from different zone of province and prepared for greenhouse cultivation. Soil physical and chemical properties such as: (texture, pH, calcium carbonate, organic matter, cation exchange capacity, and electrical conductivity) of soil were determined by routine laboratory methods. In this study, bean plant responses were investigated by application of two levels of iron (0 and 10 mg kg-1) in soil as iron sulfate in the greenhouse experiment. All of soil samples received nitrogen, potassium, phosphorus, manganese, copper and zinc as; (150, 100, 25, 5, 5, 5) mg kg-1 as solution in each pot respectively. The greenhouse study was conducted in a factorial experiment with three replications as complete randomized design. Six bean seeds were planted in pots. After the second week three plants of these six seeds were kept.
Soil moisture was maintained at field capacity. At the end of vegetative phase, the shoot bean and iron concentrations were determined in plant samples. At the end of the vegetation period, the shoot parts of plants cut, and plant responses including; (dry matter weight, Fe concentration, total Fe uptake and relative yield) (DMcontrol./DMFe fertilizer*100) were determined.
Results and Discussion: The results showed that available iron content in the soil varied from 1.5 to 20 mg kg-1 of soil with a mean value of 7.75 mg kg-1. The bean plant responded to Fe application and their relationships with physical and chemical properties of soils, which were investigated were effected too. Analysis of variance showed that the effects of soil and Fe fertilizer application were separately significant at 1% level for (weight dry matter, Fe concentration and Fe uptake). The effects of the (soil and fertilizer) interaction were significant at 1% level for the Fe concentration and Fe uptake. The mean comparison test of plant responses was significant as affected by Fe fertilizer consumption. By using Cate-Nelson graphic method, the critical level of iron in soils was five mg kg-1. Amounts of percent relative frequency indicated that eight percent of the soils were less than five mg kg-1 Fe, 63% of soils between 5 to 10 mg kg-1, 16% of soil between 10 to 15 mg kg-1 and 13% of soil above 15 mg kg-1 Fe. Plant Fe concentration in the control treatment (without Fe application) was 439.4 (mg kg-1), but at the Fe treatment (10mg kg-1) increased to (534.4mg kg-1).
The Fe uptake significantly increased from 1.54 to 2.16 mg Fe pot-1 with the application of 10 mg-Fe kg-1. The Fe uptake differences between treatments was due to increase of dry matter weight, and the plant Fe concentration, and this was due to the fertilizer application. Relative yield and dry matter weight showed positive and significant correlation with (clay, CEC and Fe available), but sand revealed negative correlation with the plant's response. The Fe uptake showed positive and significant correlation with Fe available but negative and significant correlation with the sand. The regression equation showed that Fe uptake to be related with CEC significantly.
Conclusion: By using Cate-Nelson graphic method, the critical level of iron in soils was five mg kg-1. The plant parameters were predictable significantly by soil properties such as (clay, sand, silt, soil organic carbon and Fe concentration).
leila tabande; M. R.Bakhshi
Abstract
Introduction
Among essential plant microelements, iron (Fe) exert the highest restriction of crop production in Fars Province. Trace elements in the soil is composed of forms into 5 groups. These are the water-soluble and variable, adsorbed, chelate creating with complex compounds, secondary clay minerals, ...
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Introduction
Among essential plant microelements, iron (Fe) exert the highest restriction of crop production in Fars Province. Trace elements in the soil is composed of forms into 5 groups. These are the water-soluble and variable, adsorbed, chelate creating with complex compounds, secondary clay minerals, forms insoluble metal oxide minerals, and primary minerals. Water-soluble, changeable, adsorbed or form in chelates to be present as balance in the soil is noted and to be important for plants in nutrition.
Materials and Methods
In a greenhouse experiment was done with Soybean planting, the effects of Fe chelate (FeEDDHA) fertilizer levels on William cultivar of soybean (Glycine max L.) growth and chemical composition were studied by using a completely randomized design with 3 replications. Treatments were consisted of 10 soil samples and 3 levels of Fe applications (control, 5 and 10 mg.kg-1 as Fe EDDHA). Beside some physical and chemical soil properties and Extractable iron content with DTPA and EDTA were determined. By sequential extraction methods of Singh & Sposito ( 1982), chemical forms of Iron, exchangeable iron (Exch-Fe), organic bounded iron (OM-Fe), amorph iron oxides bounded iron (AFeOX-Fe), crystal iron oxides bounded iron (CFeOX-Fe) contents of soils were determined. Then, Concentration and uptake of Fe, Mn, Cu and Zn in plant were calculated.
Results and Discussion
carbonate, organically, amorphous oxide, crystalline iron oxide bounded and residual forms of iron were 0.0053, 0.0016, 0.44, 21.1 and 78.6% of the total iron as average, respectively. Therefore, content of carbonate, organically bound iron of soil, represented only a small fraction would not be considered as important as the total iron. In other words, crystalline iron oxide bound iron and residue iron forms constitued an important part of total iron.
Considering the average iron content of the soil related to chemical forms of iron was arrenged such as:
Res-Fe>CFeOX-Fe>AFeOX-Fe>Car-Fe> OM-Fe > Exch.-Fe
Applications of Fe had significant effect on dry matter, concentration, and uptake of Fe, Zn, Cu and Mn, extractable forms via extracting DTPA, EDTA, organic and exchangeable forms in soybean compared to control. Among chemical forms of iron, organic form with the amount of available iron plant (extraction by DTPA) had significant positive correlation. Also, many of the physical and chemical properties of calcareous soils studied, were significantly correlated with some chemical forms and amount of iron uptake by plant. DTPA extractable iron had negative correlation with pH ( R2= 0.514*) and EDTA extractable iron had positive correlation with organic matter (R2= 0.428*).
Conclusions
Application of Fe EDDHA, was leaded to significant increase organic and plant available (DTPA) forms of iron and due to significant regression equation (r=0.435*) between two chemical forms of iron (organic and DTPA extracted), it can be inferred that, the bulk of available iron plant was in form of organically bound. One reason for the positive reaction to the use of Fe EDDHA, subjected to a significant increase absorbable forms of iron in the studied soils.
Keywords: Chemical and Physical properties of soil, DTPA, EDTA, Iron, Sequential extraction
