Effect on composition of duckweed (Lemna minor) of different levels of biodigester effluent in the growth medium and of transferring nutrient-rich duckweed to nutrient-free water

摘要

TwoexperimentswereconductedonaprivatefarminBinhThuyDistrict,CanthoCitytostudy:(i)theyieldandcompositionofduckweedcultivatedwithdifferentlevelsofbiodigestereffluent;and(ii)theeffectonduckweedcompositionofa#8220;shock#8221;treatmentoftransferringhighqualityduckweedtoplainwatercontainingnonutrients.Inexperiment1,thetreatmentswere6levels(0,4,8,12,16and20%)ofbiodigestereffluentaddedtofreshwaterinplasticcontainerscontainingduckweed.Thesurfaceofwaterineachcontainerwas0.4m2nbsp;with20cmdepthgivingavolumeof60liters.Duckweedwasinoculatedatarateof400g/m2.Theyieldofduckweedwasmeasuredoveraperiodof14daysbyremovingandweighingonethirdofthebiomassevery48h.nbsp;Therewasacurvilinearresponseinyield,andincrudeproteincontentoftheduckweed,tolevelofeffluentwithmaximumvaluesforbothataratioof12%effluentand88%water(72mgN/liter).nbsp;Duckweedfromthistreatmentwasthentransferredtofreshwaterandthecompositionstudiedover5days.Thecontentofstarchincreasedandthatofcrudeproteindecreasedwithincreasingtimeinthefreshwater.Itwasconcludedthatyieldandcrudeproteincontentofduckweedwasoptimizedwhentheculturemediumcontained12%biodigestereffluentand88%water.nbsp;The#8220;shock#8221;treatmentoftransferringthebestqualityduckweedtonutrient-freefreshwaterledtodecreasesincrudeproteinandcorrespondingincreasesinstarch.However,theeffectswererelativelysmallandunlikelytohavesignificancefromthepointsofviewofduckweedasafeedforducksorasasubstrateforethanolproduction.