The effect of lime on the rhizosphere processes and elemental uptake of white lupin
Al Mamun S
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Acid soils cover 30–40% of the world’s arable land and represent one of the major constraints to agricultural production. Lime is routinely added to soil to improve fertility and to reduce the solubility of elements such as aluminum (Al) and cadmium (Cd). White lupin is cultivated globally, however, this is done mainly on acidic soils because of its calcifuge characteristics resulting from its limited ability to compartmentalize calcium (Ca). In abiotic stress conditions, lupins exude organic acids and flavonoids from cluster roots. This can increase the availability of essential soil nutrients to the plant but also exacerbate the uptake of contaminants. We aimed to determine the effect of liming on the rhizosphere processes of white lupin plants in two high-fertility soils, which were treated with seven levels of lime. Nutrient availability and plant uptake was assessed with a pot experiment. Three lime levels have been chosen for a further rhizotron study. Diffusive gradient in thin layers (DGT) gels were applied on selected root zones and then analyzed by laser ablation inductively-coupled plasma mass spectrometry (LA ICP-MS). The results showed that lime affected the solubility of extractable elements and the plant uptake. In soils treated with different levels of lime, the uptake of nutrients was sufficient to avoid nutrient deficiency. However, analysis of the DGT gels only showed mobilization around the cluster root of the plant grown in the untreated soil. The results indicate that white lupin can be grown at pH as high as 7.50 with 10 wt% lime without suffering from nutrient deficiencies.