Medium nitrogen optimized Boehmeria nivea L. growth in copper contaminated soil.

Copper (Cu) pollution in agricultural soils is considered as a serious health risk due to its accumulation in plants. Thus, there is an urgent need to optimize nutrient application for higher yield with lower Cu uptake to ensure food security. A pot experiment was conducted to investigate the effectiveness of nitrogen fertilizer (N) on Boehmeria nivea growth, gas exchange characteristics, antioxidant capacity and uptake of Cu in contaminated soil. Therefore, combinations of Cu levels (0, 100, 300 mg kg-1) and N levels (0, 140, 280, 420 kg ha-1) were applied. The results showed that N at 280 kg ha-1 significantly (≤0.05) increased plant growth in terms of fresh biomass, plant height, stem diameter and number of leaves per plant up to100 mg kg-1 Cu in soil for all harvests (H1, H2, H3 and H4). However, the interactive effect of Cu and N on Cu uptake by plant varied among N levels. Furthermore, N at 280 kg ha-1 also improved the gas exchange characteristics viz., net photosynthesis (Pn), transpiration rate (Tr) and stomatal conductance (gs), while decreased oxidative stress in B. nivea up to 100 mg kg-1 Cu in soil, relative to control. Thus N at 280 kg ha-1 can be considered as an effective dose for high fresh biomass with lower Cu uptake by B. nivea grown as fodder in Cu contaminated soils (≤100 mg kg-1). Overall, present research highlighted the necessity of balanced or optimum N application for sustainable B. nivea forage production in Cu contaminated agricultural lands.