Response of duckweed (Lemna minor) growth to increasing concentrations of biodigester effluent and rubber latex wash water in the pond

 Phonepaseuth Phengsavanh (Lao)
seuth35@yahoo.com

Abstract

 An experiment was conducted to compare the growth response of duckweed (Lemna minor) to increasing concentration of N from three sources of substrates (rubber latex wash water, effluent from a biodigester installed near pig pens and mixed latex wash water with effluent in the proportion of 50:50 in fresh basis) and three levels of N (10, 20 and 30 mg/L) according to a 3 x3 factorial arrangement with 4 replications per treatment.

 Air and water temperature ranged 27-31 and 21-24^oC respectively during the test with the highest values in the midday (12:00) where average temperature values were 38 and 28^oC, respectively.

 There was not significant interaction (P = 0.259) of source of N x level of N. The source of N influenced (P = 0.001) average yield and root length of duckweed. There was a positive effect (P = 0.002) of N level of fertilization on average biomass yield and root length of duckweed. Neither mean content of crude protein (35.7% in dry basis) nor water solubility of DM (65.0%) of duckweed were significantly influenced by the source and level of N (P= 0.444 and P=0.249 respectively).

 Further studies concerning recycling materials through effluents and wash water to duckweeds are suggested in order to improve the efficiency of integrated farming systems in developing countries.

 Key word: duckweed, Lemna minor, latex wash water, pig effluent, nitrogen

Duckweed before harvesting

Harvesting and re-inoculating duckweed