Row spacing, plant population, and cultivar effects on grain amaranth in the northern Great Plains

An understanding of plant response to row spacing and plant density is important in developing effective production systems for new crops. Optimum row spacing and plant population for grain amaranth (Amaranthus spp.) production in the northern Great Plains was evaluated at Prosper and Williston, ND, over 6 station-years. Amaranth cultivars K283, K343, K432, and MT-3 were established at populations of 74 000, 173 000, and 272 000 plants ha(-1) in 30- and 76-cm row spacings. Grain and biomass yield, plant height, harvest index, harvested plant population, and plant lodging were measured. Grain yields were similar among plant populations at each of the drier environments, averaging 1050 and 410 kg ha(-1) for Prosper in 1989 and Williston in 1990, respectively. A 12% yield advantage, 160 kg ha(-1), was observed at the lowest compared with the highest plant population at Prosper in 1990, but not in 1992. The main effect of row spacing on grain yield was not significant; however, the interaction of row spacing, plant population, and environment indicated population yield ranking differences at the 30-cm row spacing among environments but not at the 76-cm row spacing. The two A. cruentus L. cultivars, K283 and MT-3, generally produced more grain than the two A. hypochondriacus L. x A. hybridus L. cultivars, K343 and K432, especially in dry environments. When considering yield, plant mortality, and potential harvest difficulties, the moderate population (173 000 plants ha(-1)), 76-cm row spacing, and generally higher-yielding A. cruentus cultivars would be recommended.