Originated soil mineral constituents as a function of supplying power capacity for nutrients at the main sediments of el fayoum depression, Egypt

Abstract EN

The current study is an attempt to define the relationship between originated mineral constituents and essential nutrients that could be derived into the formed soils under cyclic-formation sequences at El Fayoum depression.

To achieve this target, four soil sites were selected to represent some soils developed on the main parent materials, i.

e., the Nile alluvium, recent lacustrine, desert formations of siliceous (aeolian) and carbonatic in nature (Eocene limestone).

The obtained results showed wide variations in the characteristics of the studied soil sites, i.

e., topographic-sequence (-40 to + 25 m), soil texture grades (sandy to clay), CaCO3 content (1.12 to 38.54%), ground-water table depth (65 to > 150 cm), soil salinity (ECe = 1.65-23.96 Ds / m) and sodicity levels (ESP = 3.42-32.68), consequently they differ in their soil taxonomic units and the suitability classes for agricultural purposes.

Wetness, soil texture, CaCO3, gypsum and salinity / alkalinity are the most effective limitations for soil productivity, with an intensity degree ranged between slight and very severe (rating > 90 and < 40).

Also, the suitability classes of the studied soils ranged between moderately (S2s1s4n) and not suitable (N1ws1s4) for the current condition as well as highly (S1s1) and marginal suitable (S3s1s4).

The polarizing microscopic examination for light and heavy minerals of sand fraction as well as the x-ray diffractions of both silt and clay fractions were also suggested to identify the different nutrient-bearing mineral assemblages.

Moreover, soil constituent-bound nutrient forms, i.

e., exchangeable, organic matter, carbonate, manganese oxides, amorphous and crystalline iron oxides and the residual content were identified due to their crucial importance for soil fertility status.

Most of P amounts in soil were bound with organic matter fraction, with maximum values reached about 26 and 20% of total bound P-forms for both the fluvial sediments and carbonatic desert formation, respectively.

The greatest value of K bound with organic matter fraction was about 15% of total bound K-forms for the recent lacustrine sediments.

Ca and Mg were more combined with carbonate fraction, especially in the carbonatic desert formation, with greatest values of more than 39 and 68% of the total bound forms, respectively.

Relatively high S-amounts of about 30-31% of the total bound S-forms were bound with organic matter fraction of the Nile alluvial and lacustrine sediments.

A pronounced amount of bound micronutrients was more obvious in the Nile alluvial sediments, where Fe was more combined with amorphous and crystalline iron oxide fractions (i.

e., about 24 and 40 %, respectively) ; Mn was more bound with MnO2 and both iron oxides fractions with maximum values of 23.54 and 30.75 %, respectively; Zn was mostly combined with the amorphous and crystalline iron oxides fractions with about 22 and 37%, respectively ; whereas, Cu was also more related to amorphous and crystalline iron oxides fractions (i.

e., about 20 and 22 %, respectively) in the recent lacustrine sediments.

The distribution pattern of total macronutrients could be arranged in a descending order of aeolian < carbonatic desert formation < recent lacustrine < Nile allluvial sediments for P and K ; aeolian < fluvial < recent lacustrine or carbonatic desert formation for Ca, Mg and S.

Total amounts of Fe, Mn, Zn and Cu greatly differed among the studied soil sites ; the highest and lowest values were existed in the fluvial and siliceous desert formations, respectively.

The relatively highest values of these micronutrients were mainly due to the occurred high contents of organic matter, amorphous or crystalline iron oxides and clay fractions.

The available contents of the studied nutrients followed an almost similar trend to that of the total ones, except for phosphorus and micronutrients in the desert formations.

This is mainly due to the low contents of organic matter, nutrient bearing minerals and retention or adsorption process in the siliceous desert formation and/or precipitation with CaCO3 in the carbonatic one.

The statistical analysis, using the program of SPSS (1997), and obtained data of simple coefficient showed significantly correlations between each of the studied nutrients and some specific bearing-minerals in the different soil mechanical fractions with a contribution percentage.

Thus, the final goal of this work was achieved by proposing a simple relationship between the identified mineral nutrient sources and their contribution percentages for nutrients supply in soil sediments under study.