Minimization of cadmium toxicity and improvement in growth and biochemical attributes of spinach by using acidified biochar

Cadmium stress significantly affects plant growth by disrupting essential physiological and biochemical functions. It slows nutrient intake, causing slowed development and decreased biomass. Cd also produces reactive oxygen species, causing oxidative stress, which harms cell components like lipids, proteins, and DNA. This lowers chlorophyll levels, making photosynthesis difficult and stunting development. Cd's toxicity affects hormone balance, enzyme activity, and cell structural integrity, leading to poor plant growth and decreased agricultural output. Acidified biochar (BC) can effectively overcome this problem. Biochar features high cation exchange capacity (CEC) and oxygen-containing functional groups may aid in the immobilization of heavy metals in soil via surface complexation and precipitation. Cd immobilization can be increased by treating biochar with acid, which exposes additional adsorption sites. It can significantly enhance plant growth by improving soil structure, encouraging water retention, and improving microbial activity as a slow-release nutrient. This study investigates the effects of combining BC as amendments to spinach, both with Cd and without stress. Four treatments (control, 0.45BC, 0.90BC, and 1.20BC) were applied using a completely randomized design in four replications. Results showed that 1.20BC treatment showed a significant increase in shoot fresh weight (86.21%), root fresh weight (96.20%), shoot dry weight (223.24%), root dry weight (42.38%), total soluble sugar (16.05%), total soluble protein (54.70%), compared to the 0BC under 20 mg Cd/kg soil contamination. Additionally, there were notable improvements in chlorophyll a (121.26%), chlorophyll b (10.91%), and total chlorophyll (32.12%) above the control in Cd stress, also showing the potential of 1.20BC. A significant increase in N, P, and K concentrations of shoot and root of spinach was also noted, which validated the effectiveness of 1.20BC over 0BC under cadmium stress. It is concluded that applying 1.20BC can potentially alleviate the Cd-induced stress in spinach.