Optimizing sowing time for boosting productivity and nutritional quality of amaranth (Amaranthus cruentus L.) genotypes under Mediterranean climate

Currently, there is increasing interest in the cultivation of alternative grain crops, such as amaranth (Amaranthus cruentus L.) in Italy. However, few information exist for the most optimal sowing date (SD) of amaranth especially under rainfed conditions. A field-trial was conducted in Tuscany during 2018 to evaluate SD effects on amaranth genotypes (‘Kharkov’ and two new breeding lines coded ‘A-61’ and ‘A67’). The three SD were March 27 (first), April 20 (second), June 4 (third). Only the first and second SD coincided with increasing photoperiod. Cumulative Growing Degree Days (GDD) for ripening were 2282, 1990 and 1480 for the first, second and third SD, respectively. Compared to the first two SD, ground-cover was 20 % less from panicle formation in the third SD, therefore potentially less competitive towards weeds. A-67 was more “palatable” to the incidence of sugar beet flea beetle (Chaenoctema tibialis Illinger) from the earliest stages of growth. In contrast, ‘Kharkov’, was significantly less attacked by the insect over all three SD. ‘Kharkov’, demonstrated greater flexibility with stable yields of 1.3 t ha-1 for the first and second SD. In contrast, significant yield reductions (1.5 to 1.2 t ha-1, from the first to second SD, respectively) were evident for both lines of amaranth in response to SD delay. Adverse effects of the third SD, included significant decline in yield, protein content and 1000 seed mass. In conclusion, amaranth, March-April SD may be recommended for obtaining optimal grain yield of amaranth along with making it successful as a viable alternative grain crop under under agro-ecological conditions of Central Italy.