Nitrate accumulation in lemna minor on 6 different media

Duckweed is a potential alternative protein source for food and feed. However, little is known about the nitrate accumulation in this plant. A high nitrate level in vegetables can indirectly lead to an elevated intake of nitrites and N-nitroso compounds, increasing the risk of diseases for humans and animals. This research evaluated whether duckweed grown on different media accumulates nitrate beyond legal safety levels for human and animal intake. Duckweed was grown on (i) rainwater, and (ii) three synthetic media containing different nutrient levels. Furthermore, (iii) biological effluent of swine manure treatment and (iv) aquaculture effluent from pikeperch production were used, as these are potential media for closing nutrient loops in the agriculture sector. It was found that nitrate levels increased with the increasing availability of macronutrients in the water, and pH showed a particularly strong negative correlation with the nitrate levels in duckweed. Nevertheless, nitrate content of duckweed never exceeded 530 mg NO3 kg-1 fresh weight. To conclude, duckweed’s nitrate content was below safety limits for human consumption in all tested growing media; however, a potential risk for ruminants was observed as these are more sensitive to nitrate conversions in their gastro-intestinal track.

The first tab contains information on the units and the measured parameters in both the water and duckweed.