Physico‐chemical changes in bauxite residue following application of spent mushroom compost and gypsum

Abstract

Physical properties exhibited by unvegetated mine wastes pose limitations to vegetation establishment and growth. In an attempt to promote vegetation cover on bauxite residue, a field trial was established to determine the effect of spent mushroom compost (SMC) and gypsum amendment on enhancing the physical properties of the residue. SMC was incorporated at rates of 0, 60, 80 and 120 t ha À1 with gypsum at 0, 40 and 90 t ha À1 and Holcus lanatus sown at a rate of 80 kg ha À1 . The addition of SMC and gypsum was beneficial in improving the physical properties of the residue and promoting growth. Principally increasing organic content of the residue decreased bulk density and particle density whilst improving substrate porosity. Residue pH, EC and sodicity of the residue were also affected by the amendments, which positively impacted on microaggregate stability and preventing clay dispersion. Pearson correlations demonstrate that the most significant parameters in determining clay dispersion potential are the pH and the exchangeable sodium percentage (ESP) of the residue.

Phosphogypsum amendments and irrigation with acidulated water affect tomato nutrition in reclaimed marsh soils from SW Spain

“…In field experiments, an increased WUE has been observed due to an increased infiltration rate in gypsum amended soils (Amezketa et al, 2005;Tang et al, 2006), which in this pot experiment cannot be the explanation since all the irrigation water infiltrated. The increased WUE can be the result of the effect of Ca sulphate decreasing bulk density and consequently increasing porosity (Courtney et al, 2009). Nutritional effects of PG do not seem to explain differences in fresh or dry matter yield in plants because the highest PG usually resulted in a decreased concentration of some nutrients in plants, which in none of the cases were above toxicity limits in the control.…”

Relationships between soil physico-chemical, chemical and biological properties in a soil amended with spent mushroom substrate

“…Also, spent mushroom substrate-P contains higher organic matter content and lower macro and micronutrient concentrations compared to those of manures and urban wastes used as organic fertilisers (Paredes et al, 2006). The effectiveness of spent mushroom substrate as an organic amendment has been positively evaluated by Maher (1994), Jordan et al (2008), Morlat and Chaussod (2008), Ribas et al (2009) and Courtney et al (2009). However, the high contents of mineral salts of the spent mushroom substrate-AB could limit its use for growing of salt sensitive plants and its application to land in sensitive areas (Paredes et al, 2006).…”

Acid transformation of bauxite residue: Conversion of its alkaline characteristics

“…This technique is limited by the dissolved ability of gypsum and the rate of Ca 2+ release into solution [31,41]. Additionally, gypsum's dissolution rate is profoundly controlled by BET surface area and common ion effects.…”