Duckweed Research Paper

Proposal PART 2 (including literature review)
Jonathan Taylor 11TK
Ms. Maharaj
Literature review:
Lemna sp. (duckweed) species occurs throughout Africa, Asia, Europe and North America. As more leaves grow, the plants divide and become separate individuals, enabling the rapid spread of the plant. Duckweed’s optimal growth range is 20 to 28°C and a pH range of 6.5 to 7.5 (USDA, 2015).
1. Duckweed as a problem in nutrient-enriched water
Duckweed is a free-floating plant whose populations can attain nuisance levels in slow moving freshwater rivers and ponds, particularly when the water has added nutrients from human farming and industrial activities (Lynch, 2004).
Nutrients, mainly nitrogen (N), potassium (K), and phosphorus (P), are applied in

Table 1 : South African standards for levels of K, N and P that create nutrient problems in fresh water and induce eutrophication
Type of water body K (Potassium) mg/l N (nitrogen) mg/l P (phosphate mg/l
Un-impacted water body No standard >0.5 mg/l 10 – 50 mg/l
Nutrient enriched water body No standard 5 – 10 mg/l Up to 200 mg/l
Source : DWAF 1996
This information will be used as a reference point for the added K, N and P used in the experiment to be set up with Lemna.
2. Duckweed as livestock food crop
Duckweed (Lemna minor L.) has received research attention because of their potential to remove nutrient contaminants from water waters and convert it into animal food. Duckweeds can be grown on many types of water to produce a protein-rich animal feed. When grown in this way, duckweed can yield 10 – 30 tonnes dry matter/ha/year which contains up to 43 % crude protein, 5 % lipids and this all forms a highly digestible dry matter (Leng et al., 1995). Dried Lemna is used as cattle feed having up to 45% protein, 4% fat. Unfortunately, from the human point of view, it is also high in calcium oxalate which is toxic to humans. For people to eat duckweed, it would also need to be grown under sanitary conditions (Deane, 2015; Cheon and Stomp,