Bauxite-processing residue must be disposed of in specifically designed facilities for longterm management. Consideration of alkalinity, salinity, sodium content, and poor nutritional status is essential for successful rehabilitation of residue disposal areas (RDA). The aim of this study was to examine the availability and distribution of the micronutrients, B, Cu, Fe, Mn, and Zn, in (i) fresh bauxite-processing residue sand (particle size >150 μm) with and without gypsum amendment, and (ii) aged residue sand from a 4-year-old rehabilitated RDA that had received past gypsum and fertiliser addition. Samples of fresh residue sand from India and Australia exhibited high alkalinity, high salinity, and sodicity. Gypsum addition significantly lowered pH, soluble Na, and alkalinity. Aged residue sand had low levels of all micronutrients, with low extractability for Zn and Mn followed by B, Cu, and Fe. exchangeable Na, and alkalinity of residue. Nutrient management strategies that account for the characteristics of residue sand need to be developed for residue rehabilitation.Importantly, strategies to limit the conversion of nutrients to non-available forms are required to minimise micronutrient disorders.

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Assessing the ability of soil microorganisms to dissolute poorly soluble native calcite to supply Ca2+ is a new area to be explored in reclaiming sodic soils by supplying adequate Ca2+ and reducing the recurrent sodicity. Hence, the present study aimed to isolate a calcite dissolving bacteria (CDB) from calcareous sodic soils and to understand the mechanism of calcite dissolution. Of the 33 CDB isolates recovered from the calcareous sodic soils of Tamil Nadu (Coimbatore, Ramnad, and Trichy), 11 isolates were screened for calcite dissolution based on titratable acidity. 16S rRNA gene sequence analysis of the three best isolates viz., SORI09, SOTI05, and SOTI06 revealed 99% similarity to Bacillus aryabhattai, 100% to B. megaterium, and 93% to Brevibacterium sp., respectively. Among them, Brevibacterium sp. SOTI06 released more Ca2+ (3.6 g.l−1) by dissolving 18.6% of the native calcite. The spectral data of FTIR also showed reduction in the intensity of calcite (55.36–41.27) by the isolate at a wave number of 1636 cm−1 which confirmed the dissolution. Besides producing organic acids (gluconic acid and acetic acid), Brevibacterium sp. SOTI06 also produced siderophore (91.6%) and extracellular polysaccharides (EPS, 13.3 μg. ml−1) which might have enhanced the calcite dissolution.