Tillage System Influences Water Use and Water Use Efficiency of Annual Forages.

Northern Great Plains cropping systems have diversified from cereal grain-fallow to cereal grain-pulse grain over the previous two decades. However, further diversification is desirable for improved water and pest management, and additional profitability.  Annual forages, particularly cereal grain forages, may be a key component to meet these needs.  A series of short and long-term studies have addressed the influences of tillage system, cultural practices, and crop rotation on cereal forage productivity, water use (WU), and water use efficiency (WUE) in northeast Montana. In general, no-till and conventional tillage provided similar yields, WU, and WUE of awnletted barley (Hordeum vulgare L.) forage.  However, when planting date was delayed, WU and WUE decreased while weed biomass increased.  Land rolling, a mechanical method to push rocks to the soil surface to protect equipment at harvest, did not influence forage yield or WU but more than doubled density of small-seeded broadleaf weeds. Banded N fertilizer at planting provided greater WU, WUE, and nitrogen use efficiency for winter wheat (Triticum aestivum L.) and barley forages compared to broadcast N fertilization at planting.  Ecological management practices were developed to provide greater competitiveness of forage barley with weeds and included 33% greater seeding rate, banded N fertilization at planting, and taller wheat stubble at combine harvest, providing the potential for additional capture of snow melt.  Forage barley in ecological management had 28 more plants m^-2, two cm greater height, 65 more tillers m^-2, 606 kg ha^-1 greater crop biomass, 3.5 kg ha^-1 mm^-1 greater WUE, and 47% reduction in weed biomass at harvest than barley in conventional management.  Preplant and post-harvest soil water contents were similar among four tillage and management systems. Dryland forage barley with higher seeding rate and banded N fertilization in more diversified rotation produced greater yield and used water more efficiently than that with conventional seeding rate, broadcast N fertilization, and less diversified rotation. Annual cereal forages are resilient in water use (WU), water use efficiency (WUE), and weed management in diversified dryland cropping systems for semiarid prairie.