Phenological studies on cultivated amaranthus species

When cultivated amaranthus species are introduced, knowledge on the phenolo gical traits of the populations acquired (time and duration of emergence, f lowering and ripening) are required in order to decide on the mode of utili sation (seed or green fodder) and the cultivation techniques. Small-plot so wing date experiments were carried out at four locations in 1990 to test 38 populations of five amaranthus species (Amaranthus blitum L., A. caudatus L., A. cruentus L., A. hypochondriacus L,, A. tricolor L.). It was found that, besides the temperature, the characteristics of the soil surface (e.g. permeability, crust formation) were the chief factors influe ncing the emergence of amaranthus, Low temperature, like crusted or muddy s oil, delayed emergence, though there was no reduction in the number of plan ts emerging. Slow emergence increased the danger of weed infestation, Some of the species (A. blitum, A. tricolor, A. caudatus) appeared to have a fai rly high heat requirement. The onset of flowering showed variations of more than a month in the popula tions of A. caudatus and A. hypochondriacus, while there was little differe nce in the populations of the other species. The development of the amarant hus stands, which were sown in June and have a long vegetation period, was delayed by drought. The duration of flowering was found to exhibit a logari thmic correlation with the length of the inflorescence axis and to depend o n the species (A. caudatus, for example, flowers for a long period of 15-25 days, while A. Maim only flowers for 4-7 days). Seed ripening, which began 30-35 days after the beginning of flowering, irr espective of the species, occurred en masse 5-15 days later, depending on t he inflorescence morphology of the given species. The protracted nature of seed ripening is not a problem in the seed production of the highly product ive amaranthus species, but for technological reasons, the use of fast-ripe ning types is recommended when the crop is utilised as seed.