An Assessment of the Bioavailability of Metals in Soils on Oil Palm Plantations in Nigeria

Abstract

We investigated the speciation, bioavailability, and mobility of metals in soils from selected states on oil palm plantations in southwest Nigeria. Soils were analysed for total metal content and speciation on all sampling locations. Metal concentrations were compared against pH, electrical conductivity (EC) and soil organic matter (SOM), which were high at all the sampling locations. The speciation results deduced that the concentrations of the different fractions vary widely at each sampling location. Cd is mostly abundant in the exchangeable phase in all the samples analysed in the various locations. Ni in the Iresa-apa plantation (29.9%) and Co in the Acharu plantation (29.9%) also showed appreciable concentrations in the Fe/Mn oxide fractions. The concentrations of Pb and Cu were highest in the organic fraction. Metals in the organic phase are more released into soil solution when compared to the residual phase fractions. Chromium and Zinc were mostly associated with the residual phase when the values of the residual phase were compared with other geochemical fractions. The plantations under study, which recorded the highest concentrations of Cr and Zn in the residual fractions, were 87.9% (Okitipupa), 86.3% (Ikire), 82.7% (Apoje), 90.3% (Onishere), 89.7% (Benin City), and 85.6% (Nsukka).The results of the sequential extraction show that mostly Cr and Zn were strongly bound to the residual/inert phase in all the soils under investigation. The potential mobility of the metals with high fractions in the residual phase is as follows: Cr (74.8%), Zn (74.0%), Pb (73%), Fe (69.5%), Ni (67.0%), Cu (63.8%), Mn (30.5%), Co (30.7%), and Cd (25.9%). These values were high when compared to the values of other metals in the other mobile and potentially mobile fractions.

Synthetic antioxidants and metallic elements as additives/contaminants in virgin palm oil

“…Similar studies on soils sampled on the oil plantations have shown that lead is a potentially mobile element and soluble in soil water and under acidic conditions of the soil, it becomes mobile and can bio-accumulate in the palm fruit (Yasmin et al, 2000;Olafisoye et al, 2013;Olafisoye et al, 2014). A recent study on the bioavailability and accessibility of metallic elements in the soil on the oil palm plantations revealed the environmental quality of manganese in soil solution (Olafisoye et al, 2016). This shows that Manganese is bound in loose forms of precipitates to organic matter and clays in the speciation studies in the soil of the oil plantation under investigation.…”

Analisis Beberapa Sifat Kimia Tanah Terhadap Peningkatan Produksi Kelapa Sawit pada Tanah Pasir di Perkebunan Kelapa Sawit Selangkun

“…Bahan organik tanah dianggap sebagai elektron donor yang menyumbang reaksi reduksi logamlogam pada pH rendah (Olafisoye et al, 2016).…”

“…Kandungan Zn pada jenis tanah ini lebih rendah dibandingkan kandungan Zn pada tanah di Malaysia, yaitu sekitar 95 ppm (Zarcinas et al, 2004). Batas maksimum diperbolehkannya kandungan Zn dalam tanah adalah 90 ppm (Olafisoye et al, 2016). Kandungan Zn dalam tanah dapat berasal dari bahan induk, dekomposisi bahan organik, dan pupuk, pengotor pada pupuk RP yang sudah diaplikasikan selama empat tahun.…”

“…Mangan diperlukan tanaman sebagai aktivator enzim respirasi dalam reaksi metabolisme nitrogen dan fotosintesa. Mn juga diperlukan untuk mengaktifkan nitrat reduktase sehingga tanaman yang mengalami kekurangan, serta menyediakan oksigen untuk selsel di mitokondria (Olafisoye et al, 2016 Hubungan antara sifat kimia tanah dengan produksi rata-rata tandan per pohon dan berat tandan rata-rata Pada tanah pasir, pengaruh sifat-sifat kimia tanah terhadap produksi tandan per pohon memenuhi persamaan regresi: Y = 3,764 + 8,372 Al_dd -18,49 N_total + 0,255 KTK Dari hasil regresi berganda diketahui bahwa sifat kimia tanah yang paling berpengaruh terhadap produksi tandan per pohon pada tanah pasir adalah N-total dengan nilai β = 0,584. Pada dasarnya N merupakan unsur yang sangat berperan pada proses vegetatif tanaman dapat meningkatkan produksi klorofil sehingga luas permukaan daun semakin meningkat.…”

“…Faktor lainnya yang berpengaruh adalah KTK. Peningkatan KTK dapat menaikkan produksi tandan per pohon disebabkan tingginya bahan organik yang berkontribusi terhadap meningkatnya muatan negatif (Olafisoye et al, 2016). Dengan meningkatnya muatan negatif maka potensinya untuk mengikat unsur hara yang sebagian besar merupakan kation positif akan meningkat.…”