Amaranthus tricolor L. leaf yields affected by salinity, harvesting stage and harvesting methods
Single Amaranthus tricolor seedlings were transplanted into containers filled with 5 I river sand and were fertigated with a 'drain to waste' system. Plants were grown in the open under warm summer conditions. Four to six daily applications of nutrient solutions at electrical conductivity (EC) levels of 1, 2, 4 and 8 mS cm-1 were made. In a first study, two harvesting stages were used and plants were uprooted 30 and 45 days after transplanting (DAT). In a second study, two cutting heights were used at three stages. Leaves and side-shoots as well as leaf calcium and protein contents were monitored. Interactions between EC levels and harvesting stages affected most of the parameters. The optimum EC level for a high shoot: root ratio was 4 mS cm-1 30 DAT compared to 8 mS cm-1 45 DAT, Indicating that the plants adapted in time to saline conditions. The highest leaf mass was recorded at 4 mS cm-1 for both cutting heights but at 8 mS cm-1, the 25% cutting height produced significantly better yields than the more severe (50%) cutting height, illustrating that this crop can adapt to saline conditions, especially with a less severe (25%) harvesting procedure. Increased EC levels increased leaf protein content, thus increasing the value of this hardy leaf crop.