Abstract
The Understanding of the different fractions of Zinc in soils is important to effectively manage fertilizer resources due to the low availability of Zinc in the native soil worldwide. Bioavailability, uptake of Zinc by plant and its fractions depend largely on the soil parent material, the type of chemical transformation the soil has been expose to over times and some anthropogenic intervention. This study examined five different Zn pools.The distribution of Zn in soil fractions was determined for seven selected soils of South Western Nigeria. A sequential batch extraction which had been modified was used to identify Zn fractions and were separated into: the extractable zinc (Ex-Zn), zinc associated with the carbonate (CO3-Zn), the organically bound zinc (Org-Zn), sesquioxide (Ox-Zn) and residual (Res-Zn) in each soil. Total Zn was estimated as a sum of all the pools.Result showed that Zinc fractions in the soils were in this order: extractible pool (3.8%) < organic pool (13.6%) < carbonate pool (14.8%) < sesquioxide pool (22.8%) < residual pool (45.1%). The residual pool amounts for almost half of the zinc that made up the total zinc in the soil. The distribution of zinc into these pools were determined by selected physical and chemical properties of the soil; the pH, organic carbon, clay, CEC, and phosphorus. However, soil phosphorus and pH had the highest influence on the zinc in the experimental soils. The stable fraction that dominated the soil was evident in the low extractable Zn fractions in the soil. Which is an indication of the inherently low levels of the bioavailability of Zn in the selected soils used in this study.
Highlights
MethodsThe experimental soils were collected from seven locations in South Western Nigeria (Table 1)
The distribution of Zn in soil fractions was determined for seven selected soils of South Western Nigeria
The experimental soils were collected from seven locations in South Western Nigeria (Table 1)
Summary
The experimental soils were collected from seven locations in South Western Nigeria (Table 1). All samples were air dried and crushed to pass through 2 mm sieve. Soil samples were air-dried, crushed gently with pestle and mortar and sieved using 2 mm sieve to remove soil particles greater than 2 mm. The soil samples were subjected to routine analyses. The pH, total exchangeable acidity, exchangeable bases, total nitrogen, organic carbon content, available phosphorus and soil particle size distribution by methods largely described by Udo (1986). A modified version of the batch or single extraction scheme (Johnson & Petras, 1998) was used to characterize the various Zn fractions in the soils. Instead of using the same soil residue in the extraction step, fresh samples were weighed into the reagent as follows (Chirma & Yerokun, 2012):
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