Some effects of processing cow manure for fertilizing duckweed (Lemna minor)

Theng Kouch

thkouch87@hotmail.com

Abstract

An experiment was conducted to compare the fertilizing value of fresh or aerobically fermented (5 or 10 days) cow manure and biodigester effluent charge with cow faeces on agronomic characteristics of cultivated duckweed (Lemna minor). The trial was laid out in a completely randomized design, with four treatments replicated 6 times Fresh cow manure contained DM 24.5% and N 0.32% (fresh basis).

There was a positive influence (P<0.01) of fertilization on biomass yield of duckweed, the average of the four treatments equaled 75.5 g/m² per day, whereas a control without fertilization yielded 37.6 g/m² per day. There was no effect of treatment on DM and crude protein content of duckweed (on average 5.06 and 27.8% respectively).

It was encountered that the response to water pH of biomass yield in the ponds was curvilinear (R² 0.993) whereas crude protein in the duckweed biomass decreased in a curvilinear manner (R² 0.990) with increasing DM content in the macrophyte. 

The aerobic fermentation of cow manure appears to be a viable alternative for duckweed cultivation in those farms were biodigester effluents are not currently available. It is recommended to further evaluate the integration of cow manure to aquaculture in integrating farming systems, in order to optimize this subsystem.