Effect of compost addition on arsenic uptake, morphological and physiological attributes of maize plants grown in contrasting soils

Contamination of soils with arsenic (As) represents a global environmental and health issue considering the entrance of toxic As in the human food chain. Although partially understood, addition of compost for the remediation of As-contaminated soils may result in distinct effects on plant growth and physiological attributes depending on compost-mediated potential mobility/sequestration of As in soils. This study explores the role of compost addition (C; 0, 1 and 2.5%) on morphological and gas exchange attributes and photosynthetic pigments (chlorophyll contents) of maize plants under As stress (0, 40, 80, 120 mg kg(-1)), as well as soil As immobilization/mobilization in a pot experiment, using two contrasting soils. Results revealed that, in Narwala (sandy loam) soil, the addition of compost decreased shoot As concentration of maize plants (p < 0.05; 4.01-13.7 mg kg(-1) dry weight (DW)), notably at C-2.5 treatment, with significant improvement in shoot dry biomass, gas exchange attributes and chlorophyll (a and b) contents, i.e., 1.33-1.82, 1.20-2.65 and 1.34-1.66 times higher, respectively, over C-0 at all As levels. Contrastingly, in Shahkot (clay loam) soil, C-2.5 treatment increased shoot As concentration (p < 0.05; 7.02-17.3 mg kg(-1) DW), and as such reduced the shoot dry biomass, gas exchange attributes and chlorophyll contents, compared to the control-rather C-1 treatment was more effective and exhibited positive effect than C-2.5. Considerably, at C-2.5 treatment, phosphate extractable (bioavailable) soil As concentration was also found to be greater in the (post-experiment) Shahkot soil than that of Narwala soil (0.40-3.82 vs. 0.19-1.51 mg kg(-1), respectively). This study advanced our understanding to resolve the complex compost-As interactions in As-contaminated soils, which are imperative to understand for developing the effective and soil-specific remediation strategies.