Abstract:
Aluminum (Al) is a copious element in the earths crust, typically causing high acidity in soil-plant systems. However, there is limited knowledge about its beneficial role in enhancing mineral nutrient availability and acquisition in cassava. This research examined the impacts of Al levels (0‒100 µmol Al L‒1 ) on proton and organic acid release from the roots of RY9 and KU50 cultivars under acid-washed sand microcosm for 30 and 60 days. Consequential effects of the Al were examined on the extractability of Al and selected nutrients (Fe and P) in the rhizosphere and bulk sands and the nutrient uptake in the plant. The data from 30 days demonstrated that the highest Al level significantly (P<0.05)demoted root biomass (8.53 g) but promoted the proton release from roots (2.03 µmol h1 g 1 fresh weight) compared to the control treatment (11.92 g and 0.40 µmol h1 g 1 fresh weight, respectively). Water-extractable Al and Fe concentrations in the rhizosphere sand were higher by 188‒ 276% and 201‒291%, respectively than bulk sand under the highest Al level. The moderate Al levels (< 50 µmol Al L‒1 ) increased Fe accumulation in the roots and shoots. The main organic anions released from the roots were oxalate and tartrate, which were cultivar-dependent. The 60 days data showed a similar pattern to those of 30 days. Overall, this study highlighted that moderate Al levels showed the benefits of Al in promoting proton release from roots, enhancing Fe availability in the rhizosphere zone, and Fe acquisition in the cassava plant. However, long-term exposure of cassava to high Al concentrations can progressively cause strong acidity and metal (phyto)toxicity in soil systems, which can harm the sustainability of crop production.