|KANDEL, TANKA - Oklahoma State University|
|ROCATELI, ALEX - Oklahoma State University|
Submitted to: Cogent Food & Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2019
Publication Date: 2/7/2019
Citation: Kandel, T., Gowda, P.H., Northup, B.K., Rocateli, A. 2019. Impacts of tillage systems, nitrogen fertilizer rates and a legume green manure on light interception and yield of winter wheat. Cogent Food & Agriculture. https://doi.org/10.1080/23311932.2019.1580176.
Interpretive Summary: Winter wheat is the major crop in the US Southern Great Plain (SGP) including Oklahoma and Kansas. Use of inorganic nitrogen (N) fertilizers is common for production of winter wheat in the region. However, increasing fertilizer costs and environmental awareness has generated interest in legumes as green manures to supply N for winter wheat. In this study, we compared response of winter wheat to cowpea as green manure and three rates of inorganic fertilizers under both no-till and conventional tillage managements. Crop growth of winter wheat was monitored non-destructively by canopy reflectance at 1–2 weeks intervals throughout the growing season. Total aboveground dry matter yield of winter wheat was measured at the end of growing season. Effect of tillage management on winter wheat growth was not strong and inconsistent at two study sites. However, growth and yield were strongly influenced by N-treatments. Crop growth and biomass yield of winter wheat increased with increasing amounts of applied inorganic N but cowpea did not support winter wheat growth effectively.
Technical Abstract: Combining conservation tillage with cover crops is an increasingly popular practice for crop production in the U.S. Southern Great Plains (SGP). These practices are thought to improve soil conditions, crop productivity, and reduce the environmental footprint of agriculture. This study investigated interactions between form of tillage [no-till (NT) vs conventional tillage (CT] and source and amounts of nitrogen (N) fertilization (0, 45, 90 kg N ha–1 yr–1 in inorganic N fertilizer, and cowpea as green manure) on radiation interception and efficiency, and dry matter (DM) yield of winter wheat. The study was conducted at two sites during the 2016–2017 growing seasons of winter wheat. Crop growth was monitored non-destructively by canopy reflectance at 1–2 weeks intervals (21 campaigns) and fraction of intercepted photosynthetically active radiation (fPAR) was derived by measuring canopy reflectance. Total cumulative intercepted PAR (IPAR) during the cropping period was calculated as a product of global radiation and fPAR. Radiation use efficiency (RUE) was calculated as the biomass yield to IPAR ratio. At both sites, N treatments had stronger influences on DM yield than tillage system. The RVI, IPAR and DM yield were normally higher under 90-N treatments followed by 45-N treatment. Responses of cowpea and control-treated plots were similar and the lowest. Radiation use efficiency and root/shoot ratios were not influenced by tillage system or N treatments. In conclusion, NT management did not produce IPAR and RUE above CT, and cowpea as green N source was not effective in supporting winter wheat.