Overview
This pot experiment from Bidhan Chandra Krishi Viswavidyalaya (India) evaluated the efficacy of yellow gypsum (YG), an industrial by-product of steel manufacturing, in reducing arsenic (As) bioavailability to groundnut (Arachis hypogaea, cultivar TG-51) and boro-rice grown in soils spiked with 17 levels of arsenic (0 to 24.0 mg/kg). Three YG application rates were tested: 0, 30, and 60 kg/ha. The study ran for two consecutive growing seasons and measured extractable soil arsenic at multiple crop growth stages.
The principal finding is that YG application at 60 kg/ha significantly reduced extractable soil arsenic at all growth stages and was more effective than lower doses. The reduction mechanism is attributed to increased soil Ca, Fe, S, and Mn concentrations that compete with or sorb arsenic onto soil particles. The study tracks soil extractable arsenic, soil parameter ratios (Ca:As, Fe:As, S:As), and reports these as indicators of arsenic bioavailability to crops.
This paper does not report market-level arsenic concentrations in groundnut grain. It is an agronomic intervention study under extreme artificial As contamination (up to 24 mg/kg added As, versus typical agricultural soil background of well under 20 mg/kg without spiking). The paper provides mechanistic evidence for soil-arsenic-to-crop transfer in groundnuts and characterizes intervention strategies, not baseline market occurrence.
Key numbers
Soil extractable arsenic under control conditions (no YG, Y0) across treatment levels (spiked arsenic added, mg/kg soil): range 11.44 to 21.96 mg/kg at pegging stage and 11.30 to 21.84 mg/kg at harvest. These are soil, not grain, values.
Effect of YG at 60 kg/ha versus control on soil extractable arsenic:
- Groundnut, pegging stage: mean soil extractable As of 15.69 mg/kg (Y60) vs 17.40 mg/kg (Y0); reduction of 9.81% from initial As content
- Groundnut, harvest stage: mean soil extractable As of 16.21 mg/kg (Y60) vs 17.26 mg/kg (Y0); reduction of 11.85%
- Boro-rice, maximum tillering: 13.96 mg/kg (Y60) vs 16.80 mg/kg (Y0); reduction of 16.95%
- Boro-rice, harvest: 13.33 mg/kg (Y60) vs 16.63 mg/kg (Y0); reduction of 19.85%
Soil parameter correlations under groundnut: extractable As negatively correlated with Ca (r = -0.603, p < 0.01), Fe (r = -0.246, p < 0.01); positively correlated with S (r = 0.175, p < 0.05). The Ca:As ratio ranged 19.9 to 57.4 under groundnut; highest ratio under Y60 treatment (mean 33.8), lowest under Y0 (mean 26.8), indicating improved immobilization of arsenic with gypsum.
Arsenic translocation to grain: the paper cites literature reporting that in legumes the rate of arsenic translocation to grain is low and that most As absorbed is retained in roots. The paper itself does not tabulate groundnut grain arsenic concentrations.
Methods (brief)
Factorial pot experiment (Completely Randomized Design). Soil collected from rice fields in Panchpota, Nadia district, West Bengal, India. Soil spiked using sodium arsenite (NaAsO2) with 17 levels of added As and equilibrated for one month before planting. Pots: 20 cm diameter earthen pots, 5 kg soil each. Groundnut cultivar: TG-51; boro-rice grown in subsequent season. Yellow gypsum sourced from Linz-Donawitz steel slag treated with sulfuric acid. Soil extractable arsenic measured by standard soil extraction methods. Statistical analysis: Factorial CRD with Duncan’s Multiple Range Test at 5% significance (OPSTAT software).
Implications
This paper does not contribute market-level peanut grain arsenic data. Its contribution to the peanuts literature is mechanistic: arsenic translocation from soil to groundnut grain is low because legumes restrict As transport to grain via the phloem pathway; soil arsenic bioavailability (and therefore crop uptake) can be reduced by soil amendments that increase Ca, Fe, S, and Mn availability. These findings support sourcing from agricultural regions with lower soil arsenic background and affirm that gypsum and Ca-rich soil management can reduce arsenic entry into the peanut supply chain.
Provenance notes
Open access under CC BY-NC 4.0 (Elsevier/Heliyon). Published online 16 February 2024. DOI 10.1016/j.heliyon.2024.e26530. Authors are affiliated with the Department of Agricultural Chemistry and Soil Science, Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, Nadia, West Bengal, India.
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