Grain Amaranth Seeding Dates in the Northern Great Plains

An understanding of crop response to planting date is essential when evaluating a potential new crop. A field study was designed to determine the optimum range of planting dates for dryland grain amaranth ( Amaranthus cruentus L. and A. hypochondriacus L. ✕ A. hybridus L.) in the Northern Great Plains. Four grain amaranth cultivars, diverse for plant height and branching, were evaluated over four consecutive years from 1989 to 1992 at Prosper (46°58′ N, 97°4′ W, elevation 220 m) in North Dakota. Soil types at the test site are a complex of Perella (fine‐silty, mixed, superactive, frigid Typic Endoaquolls) and Beardon (fine‐silty, mixed, superactive, frigid Aeric Calciaquolls). Four or five planting dates were selected, ranging from 1 May to 1 July at approximately 15‐d intervals. Year‐to‐year differences in weather influenced the response of amaranth to planting date for grain yield, days to anthesis, harvest index, plant height, final plant population, and lodging. Plants sown in mid‐June produced the greatest grain yield in 1989 and 1990, when near‐ or above‐average temperatures occurred throughout most of the growing season. Seedling survival was greater with later planting dates in all years except 1989, when excellent stands were achieved with all planting dates. Greatest yields in 1992, an unusually cool year, were produced with May planting dates; in that year, most plants sown in mid‐June did not mature before first frost. Material planted on 1 July failed to mature in both 1991 and 1992. In years with near‐ or above‐average temperatures, the mid‐June planting date was best for maximizing both stand establishment and grain yield. Given the uncertainty in predicting weather conditions, planting in early June in the Northern Great Plains should achieve good stands and produce high grain yields, while minimizing the risk of yield loss associated with cool condition.