AN AGRONOMIC STUDY OF THE FEASIBILITY OF CONTINUOUS WINTER WHEAT PRODUCTION IN WESTERN NEBRASKA

The reason for failure of continuous wheat (Triticum aestivum L.) cropping in the Central Great Plains was low soil moisture levels at seeding. However, most of the data with continuous wheat cropping were obtained before improvements in soil water conservation techniques were made. This study tested the hypothesis that continuous winter wheat would be a feasible alternative to fallow-wheat in western Nebraska and similar areas of the Central Great Plains. Two approaches were used to test this hypothesis: (1) A two-year field experiment was conducted to study the effects of different tillage methods (no-till, subtill, chisel, and moldboard plow) on soil water storage and yields of continuous wheat grown on three soils of different depths (60, 120, and 180cm). (2) A wheat growth and development model was used to simulate yields for 50 years of generated weather data for western Nebraska. Both continuous and fallow-wheat were simulated and within each system no-till and conventional tillage were compared. In the shallow soil, there were no differences among tillage methods in soil water content at seeding and wheat yields. In the moderately deep and deep soils, significantly more water was present in the top 60 to 90cm of soil with no-till than with the other tillage methods. Grain yields were highest with no-till in 1981 but not in 1982. Very high water storage efficiencies (up to 77%) were achieved in the deep soil between wheat harvest and seeding in 1980 and 1981 with no-till. In the simulation study, higher yields and lower incidence of failure were achieved with no-till than with conventional tillage in continuous wheat while in fallow-wheat these two tillage methods were similar. Continuous wheat repesented 69 and 89% of fallow-wheat yields with conventional tillage and no-till, respectively. These results suggest that continuous winter wheat with no tillage between harvest and seeding and herbicidal weed control can be grown successfully in western Nebraska