CHANGE IN LETTUCE NUTRIENTS, SOIL ENZYMES, SOIL MICROBIAL BIOMASS, AND ACTIVITIES UNDER CHROMIUM TOXICITY

The toxicity of heavy metals in the soil plays a detrimental role in microbial activities. Higher concentrations of Cr causes restriction of enzyme secretion in soil by disturbing the microbial population and proliferation. On the other hand, the cultivation of crops in such Cr-contaminated soils also caused a significant decline in nutrient uptake in the plants. That's why the current pot study was conducted to explore the impacts of different Cr application rates on soil enzymes activities and lettuce plants' nutrient concentration. A total of 6 treatments were applied in 5 replicates. The treatments include T0 =control (no Cr), T1=50 mg, T2=100 mg, T3=150 mg, T4=200 mg, and T5=250 mg Cr/kg soil. Results showed that increasing concentration of Cr toxicity caused a significant decrease in SMBP, SMBS, alkaline phosphatase activity, and arylsulphatase over control. A significant decline in macronutrient N, P, K, Ca, and Mg concentration in lettuce validated the negative impacts of Cr on lettuce when cultivated in Cr toxicity, i.e., 50, 100, 150, 200, and 250 mg Cr/kg soil. The increasing level of Cr also significantly minimized the concentration of Zn, Cu, Mn, Fe, and S in lettuce when grown in Cr- contaminated soil. In conclusion, increasing Cr toxicity is inversely related to soil enzymes activities and lettuce nutrient uptake. More in-depth investigations are required to explore the impacts of Cr on nutrient uptake in crops and enzyme activities in soil under different soil textures and cultivated crops type.