How amending calcareous soils with municipal solid waste compost affects Fe fractionation and availability to plant

The solubility of iron (Fe), as an important micronutrient for plant growth, is not high in the calcareous soils, and hence efficient methods must be used to increase its availability for plant use. Accordingly, a two-year research work was conducted to investigate the effects of composted municipal solid wastes (MSW) on Fe accumulation and fractionation in a calcareous soil. Treatments including MSW levels at (0 (control), 15 (MSW1), 30 (MSW2) and 60 (MSW3) t ha−1 dry weight) and usage time (yearly (T1) or biyearly usage (T2)) were tested in a factorial experiment on the basis of a completely randomized block design with three replications. The compost was salty and contained the total Fe of 16200 mg kg−1. The concentrations of plant available Fe fractions including the exchangeable (EX), carbonates-bound (CA), organically-bound (OM), and Fe-Mn-oxide-bound (FM) as well as the residual (RE), DTPA- and Total-Fe fraction were determined. MSW increased levels significantly enhanced Fe concentration in different soil fractions as the least and the highest Fe concentrations were resulted by the control and the MSW3 treatments, respectively. The effects of T treatment were also significant on different Fe fractions excluding CA fraction. The Fe fractionation using the Tessier consecutive extraction method indicated the following order of Fe distribution and concentration in different soil fractions: RE > FM > OM > CA > EX. Iron was mostly found in the following fractions RE (>90%), FM (>6%) and OM (>2%). Different soil properties including EC (positively), pH (negatively), CEC (positively) and organic matter (positively) were highly and significantly correlated with different Fe fractions indicating how the use of MSW can affect the properties of calcareous soils. It is possible to increase Fe availability in different soil fractions using composted municipal solid wastes, which is of agronomical, health and environmental significance.