Status of some nutrients and heavy metals with relations to their bearing minerals in the soils of Nile terraces at Assiut, Egypt

Abstract EN

Nine soil profiles were selected from various Nile terraces located south Assiut barrage at Assiut city, Egypt to a) examine levels and distributions of some available nutrients (P, K, Fe, Mn, Zn and Cu) and some heavy metals (Ni, Pb and Cd), b) clear up their relations with some physical and chemical soil properties, and c) evaluate their relations to their bearing minerals in the soils of the most recent and old Nile terraces.

Results showed soil available phosphorus values are higher in the oldest terraces on both Nile sides than in the youngest ones.

However, most soil layers of the youngest Nile terraces show greater available potassium levels than the oldest ones.

The recent and old Nile terraces soils exhibit very high level of P and medium amounts of K.

In most cases, there are no consistent changes in the levels of either available phosphorus or potassium with depth.

Highly significant positive correlations were obtained between the available P and K and soil contents of silt, clay, organic matter and CEC.

On the other hand, highly significant negative correlations were recorded with sand, pH and CaCOs contents.

Significant positive correlations were found between the phosphorus levels and both monazite and the sum of apatite + monazite minerals.

However, insignificant, positive correlations between available potassium and its bearing minerals were recorded, except the case of feldspars in the clay fraction was a highly significant, positive correlation.

The highest levels of DTPA-extractable Fe are obtained in the oldest Nile terrace soils.

Whereas, extractable Mn levels are high in the youngest terraces on both Nile sides.

Moreover, the soils of the youngest and oldest terraces are Fe and Mn sufficient However, most soils of the terrace bench in the interference zone and the terrace rear suture in desert fringes are considered Fe and Mn deficient The levels of soil extractable Cu are quite variable among the youngest and oldest Nile terraces, and all the investigated soils are Cu-nondefl-clent On the other hand, most examined soils are considered Zn-defldent No clear pattern of distributions of these investigated mlcronutrlents was observed with depth.

Highly significant positive correlations expressed the relations between fine particles, organic matter and CEC contents and extractable Fe, Mn and Cu.

However, highly significant negative correlations were observed with amounts of sand, CaCOs and soil pE The DTPA-extractable Zn did not show any significant correlations with all the considered soil properties.

The extractable Fe and Cu showed highly significant positive correlations with epidotes, biotite and feldspars of both sand and clay fractions.

Also, the extractable Mn has significant positive correlations with epidotes, hornblende, smectites and chlorite.

However, tow positive correlations occurred between the extractable Zn with both hornblende and pyroxene.

Generally, DTPA-extractable Nl and Pb are slightly higher in the youngest Nile terrace soils than in the oldest ones, without any clear trend of their distributions with depth.

Moreover, the youngest and oldest Nile terraces soils contain similar vey low amounts of extractable Cd.

Correlations between extractable Ni and