Submitted to: Columbia Basin Agricultural Research Annual Report
Publication Type: Experiment Station
Publication Acceptance Date: May 10, 2005
Publication Date: June 1, 2005
Citation: Albrecht, S.L., Skirvin, K.W., Long, D.S. 2005. Winter wheat responses to nitrogen fertilization in a direct-seed, summer-fallow management system. pp. 87-91. In 2005 Dryland Agricultural Research Annual Report. D.A. Long, S.E. Petrie, and P.M. Frank, eds. SR 1061. Corvallis, OR: Oregon State University Agric. Exp. Station in cooperation with USDA-ARS, Pendleton, OR. Interpretive Summary: The light soils of the Columbia Plateau are easily eroded by both wind and water. Conservation tillage practices that retain crop residue on the soil surface may decrease soil erosion in this area. However, little is known about how the adoption of conservation management practices will affect cereal production. A field experiment, incorporating a conservation tillage system, was conducted from 1998 through 2004 at the Pendleton Experiment Station to study effects of tillage and of nitrogen fertilization rates on winter wheat yields. Wheat was grown without tillage (direct-seed) with fertilizer N rates of 0, 40, 80, 120, and 160 pounds per acre. Conventional tillage (plowing) plots with fertilizer N rates of 0 and 120 pounds per acre were established for comparison. Wheat yield were significantly affected by tillage, nitrogen fertilization, and precipitation. In the direct-seed system, the 160 pound nitrogen per acre treatment had the greatest grain yields. Wheat yields had a linear response to nitrogen fertilization up to 80 pounds of nitrogen per acre, but the response leveled off at greater nitrogen fertilization rates. Based on the seven-year averages, from 1998 to 2004, yields of wheat with no fertilizer nitrogen were 57 percent greater from a conventional system than in a direct-seed management system. However, when both management systems received nitrogen fertilization at 120 pounds nitrogen per acre the seven year average for conventional tillage was only seven percent greater than direct seed. After conversion from a conventional system to a direct-seed management system, grain yields did not decrease over time. Overall, wheat yields from direct-seed plots with adequate nitrogen fertilizer nitrogen were similar to yields from conventionally-managed plots with equivalent nitrogen levels.
Technical Abstract: The silt loam soils of the Columbia Plateau contain little organic matter and are easily eroded. Conservation tillage may decrease erosion on these soils; however, little is known about how the application of a conservation management system, such as direct-seed, will affect wheat production. A field experiment, utilizing direct-seed, summer- fallow management, was conducted from 1998 through 2004 at the Pendleton Experiment Station to study effects of tillage and of nitrogen (N) fertilization rates on winter wheat (Triticum aestivum L.) yields and soil properties. Wheat was grown without tillage (direct-seed) with fertilizer N rates of 0, 40, 80, 120, and 160 lb/acre. Conventional tillage (plow and rod-weeding) plots with fertilizer N rates of 0 and 120 lb/acre were established for comparison. Tillage, N fertilization, and precipitation all affected wheat yield. Based on the 7-year averages from 1998 to 2004, yields of wheat with no fertilizer N were 57 percent higher under conventional till than under direct-seed. However, wheat yields at the 120 lb/acre N fertilization rate produced only 7 percent higher yields with conventional tillage over 7 years. In direct-seed, 160 lb N/acre had the greatest grain yields. The 7-year average yield for plots with a more recent transition to direct-seed was 91 bu/acre, whereas the longer-established plots, begun 16 years earlier, yielded 87 bu/acre. After conversion from a conventional system to a direct-seed management system, grain yields, although slightly lower than in a conventionally-tilled system, did not decrease over time. Grain yields from direct-seed plots with adequate fertilizer N were 95 percent of yields from conventionally-managed plots with equivalent N levels.