Cultivation of Lemna gibba under desert conditions. I: Twelve months of continuous cultivation in open ponds

Duckweed, Lemna gibba, was grown in 12 m² shallow ponds in the Negev desert, during 12 months of continuous cultivation, beginning April 1984. Average monthly growth rates varied with the season of the year. The lowest daily yield, 2·6±0·4 g dry weight m^-2 day^-1, was obtained during January. Highest daily yields, 7·9±2·6 g dry weight m^-2 day^-1 and 7·0±1·2 g dry weight m^-2 day^-1, were obtained during September and May. A 35% decline of the yield was seen during midsummer (July), 4·8±1·2 g dry weight m^-2 day^-1. The average rate for the year was 5·15±1·7 g dry weight m^-2 day^-1. The protein content of the plants ranged from 30 to 38% per unit dry weight. Growth performance is discussed in relation to the prevailing climatic conditions.