Water Use Patterns of Grain Amaranth in the Northern Great Plains

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Abstract
An understanding of water use is essential for evaluating the potential of new crops in areas where water is a limiting factor. This study was conducted to determine water use efficiency (WUE), depth of soil water extraction, and other agronomic characters of grain amaranth (Amaranthus spp.) produced in the northern Great Plains. Field experiments were conducted with four grain amaranth cultivars at Prosper, ND, during the 1989 through 1992 growing seasons. Volumetric soil water content was monitored with a neutron probe at eight soil profile depths during each growing season. Significant differences among cultivars were observed for biomass yield, biomass WUE, plant height, and harvest index (HI). The year × cultivar interaction was significant for grain yield, grain WUE, plant height, and HI. Maximum effective depth of soil water extraction was 122 cm in the less water‐stressed years, 1990 and 1992, and 154 cm in the more water‐stressed years, 1989 and 1991. Cultivars did not differ significantly for depth of soil water extraction or total water use (TWU). Maximum effective rooting depth occurred at early to full anthesis in 1989, 1990, and 1991 and at the late anthesis to grain fill stages in 1992. Approximately 70 to 75% of TWU occurred by the end of anthesis. Mean TWU and grain WUE values were 267 mm and 5.9 kg ha−1 mm−1, respectively. Amaranth's apparent ability to respond to water stress by increasing rooting depth makes it a potentially useful crop in North Dakota where soil moisture conditions vary considerably among growing seasons.