Tillage and nitrogen rate effects on winter wheat yield in a wheat-sorghum rotation

Authors: MAJRASHI, MOSAED - King Saud University; OBOUR, AUGUSTINE - Kansas State University; MOORBERG, COLBY - Kansas State University; LOLLATO, ROMULO - Kansas State University; HOLMAN, JOHNATHON - Kansas State University; DU, JUAN - Kansas State University; Mikha, Maysoon; ASSEFA, YARED - Kansas State University

Submitted to: Canadian Journal of Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/9/2023
Publication Date: 9/8/2023
Citation: Majrashi, M.A., Obour, A.K., Moorberg, C.J., Lollato, R.P., Holman, J.D., Du, J., Mikha, M.M., Assefa, Y. 2023. Tillage and nitrogen rate effects on winter wheat yield in a wheat-sorghum rotation. Canadian Journal of Soil Science. https://doi.org/10.1139/CJSS-2023-0028.
DOI: https://doi.org/10.1139/CJSS-2023-0028

Interpretive Summary: Winter wheat is widely grown in central Great Plains region of the United States. Water and nitrogen are the most limiting factors affecting dryland wheat and other grain production in this region. Water availability depends on precipitation and soil moisture storage. Nitrogen availability in soils can be readily increased by fertilizer application. Both these factors also interact with tillage intensity. The global increase in fertilizer prices require tillage and nutrient management practices that ensure sustainable production to improve crop nutrient use efficiency (NUE), enhance yield, reduce input costs, reduce nutrient losses, and improve food availability to the growing population. We quantified how tillage practices and N fertilizer rates affected yield and NUE in a winter wheat-grain sorghum-fallow (W-S-F) rotation over the 2015-2018 growing seasons. We found a significant wheat yield response to N rate and growing season environment. Averaged across tillage practices, wheat yield increased by 13.9, 8.3, 20.3, and 22.9 lb/ac for every 0.89 lb N/ac increase. Yields were 7-9% greater for conventional tillage (CT) than no-tillage (NT) or reduce tillage (RT). Winter wheat removed about 46.4 lb N/ac from the unfertilized control treatment. Finally, wheat yield increased by 1.78-2.23 lb/ac for every 0.04-inch increase in precipitation during the fallow period. We concluded that wheat yield response to N is highly dependent on growing environment, and NT required greater N fertilization than CT and RT to obtain similar yields.

Technical Abstract: Tillage practices, precipitation (fallow and growing season) and application of nitrogen (N) fertilizer can impact dryland (rain-fed) winter wheat yields in the central Great Plains region of the United States. The objectives of this study were to quantify long-term tillage practice and N fertilizer rate effects on yield and N use in a winter wheat-grain sorghum-fallow (W-S-F) rotation. The experimental design was a randomized complete block with split-split-plot arrangement. The main plots were crop rotation phases (W-S-F, S-F-W, and F-W-S), sub-plots were tillage practices [conventional tillage (CT), reduced tillage (RT), and no-tillage (NT)], and the sub-sub-plots were N rates 0, 45, 90, and 134 kg ha-1. There was a significant wheat yield response to N rate by environment interaction. Wheat yield increased at rates of 15.6, 9.3, 22.8, and 25.7 kg ha-1 for every kg N ha-1 increase in very low (average yield= 1974 kg ha-1), low (~2500), high (~2800), and very high (~4400) yielding environments, respectively. On average, winter wheat yields were 7-9% greater for CT compared with both NT and RT. Winter wheat removed about 52 kg N ha-1 from the unfertilized control treatment, but wheat N uptake varied by N rate and environment. Nitrogen use efficiency, N agronomic efficiency, and applied N recovery decreased at higher N rates. Across environments, wheat yield increased by 16, 20, and 17 kg ha-1 for each additional kg ha-1 N applied under CT, NT and RT, respectively. Wheat yield increased by approximately 2-2.5 kg ha-1 for a mm increase in precipitation during the fallow period. We concluded that wheat yield response to different N rates is highly dependent on growing environment, and NT required greater N fertilization than CT and RT to obtain similar yields.