The detoxification effect of liquid digestate on vanadium toxicity to seed germination and seedling growth of dog's tail grass

Dog's tail grass (Setaria viridis) presented strong tolerance and high accumulation of vanadium in field conditions. Liquid digestate containing high levels of nutrients could alleviate vanadium toxicity and accelerate the growth of dog's tail grass. To elucidate the detoxification potential and mechanism of liquid digestate, dog's tail grass was grown in soil solution containing 0.14-55.8 mg L-1 of vanadium. Parameters including germination index (GI), tolerance index (TI), seedlings' fresh weight, seedlings' vanadium accumulation, antioxidant enzymes activity, malonaldehyde (MDA) content, and V5+ species, were measured after addition of 1%, 5%, 10% and 15% liquid digestate. The results showed that a vanadium level of 10.9 mg L-1 was a threshold value for toxicity; furthermore, the GI and TI decreased by 50% when vanadium content reached 36.8 mg L-1 The MDA content was reduced, and the other parameters were markedly enhanced, after addition of 5% and 10% liquid digestate with vanadium levels above 36.8 mg L-1.V5+ species was the dominant vanadium species in solution and the addition of liquid digestate reduced V5+ concentrations. The detoxification of vanadium by liquid digestate was a combined effect of direct reduction of V5+ species and plant nutrition.