Agronomy of Dryland Corn Production at the Northern Fringe of the Great Plains

Abstract

The farming systems of the semi-arid northern Great Plains, including the Canadian Prairies, suffer from overdependence on a narrow range of crops, particularly wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.). Diversification of economically competitive cropping would greatly enhance the long-term viability and sustainability of agriculture in this large and important region of North America. The expansion of corn (Zea mays L.) production into the coolest and driest fringe of the northern Great Plains (e.g., southern Alberta) represents one attempt at diversification. This expansion has largely been on irrigated land, but semi-arid dryland production of corn appears promising. Eight years of research on dryland corn in southern Alberta focused on hybrid evaluation, irrigated and dryland comparisons, genotypic responses to drought and density stress, optimum plant density, paired row studies, weed control trials, and a 3-yr farm-scale study of three corn-based rotations. Grain yields of 35 bu/acre on summerfallow were obtained with currently available hybrids for the 2840 growing-degree-day (GDD) area around Medicine Hat in southern Alberta. Hybrids that yielded well on irrigation tended to yield well on dryland, and the hybrid most tolerant of stress on dryland had a short anthesis-to-silking interval. Optimum plant densities on dryland are about 12 000 plants/acre, compared with 24 000 on irrigation (annual rainfall of 14 to 16 in.). Dryland yields were more variable than irrigated yields; the lowest yields on dryland were 31 bu/acre (37% of the highest yields), whereas with irrigation the lowest yields were 81 bu/acre (66% of the highest yields). Averaged over five location-year combinations, paired rows (two rows 8 in. apart on 30-in. centers) resulted in a 10 bu/acre advantage over conventional 30-in. rows. The low crop density on dryland allowed late flushes of Russian thistle (Salsola iberica Sennen and Pau) and kochia, [Kochia scoparia (L.) Schrad.] to flourish. A herbicide combination to control this was identified: pre-plant atrazine combined with postemergence 2,4-D. Rotation results indicated that corn after corn yielded 18 bu/acre vs. 35 bu/acre for corn after fallow (similar to cereal yields). Corn shows potential as an alternative dryland crop on the fringes of the northern Great Plains, and may find its place either in a corn-fallow rotation or in a winter wheat-corn-fallow rotation.