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Winter wheat yield and nitrous oxide emissions in response to cowpea-based green manure and nitrogen fertilization

Published online by Cambridge University Press:  11 October 2019

Tanka P. Kandel*
Affiliation:
Department of Plant and Soil Sciences, Oklahoma State University, Stillwater, OK74078, USA
Prasanna H. Gowda
Affiliation:
Forage and Livestock Production Research Unit, USDA-ARS Grazinglands Research Laboratory, El Reno, OK73036, USA
Brian K. Northup
Affiliation:
Forage and Livestock Production Research Unit, USDA-ARS Grazinglands Research Laboratory, El Reno, OK73036, USA
Alexandre C. Rocateli
Affiliation:
Department of Plant and Soil Sciences, Oklahoma State University, Stillwater, OK74078, USA
*
*Corresponding author. Email: tanka.kandel@okstate.edu

Abstract

The aim of this study was to compare the effects of cowpea green manure and inorganic nitrogen (N) fertilizers on yields of winter wheat and soil emissions of nitrous oxide (N2O). The comparisons included cowpea grown solely as green manure where all biomass was terminated at maturity by tillage, summer fallow treatments with 90 kg N ha−1 as urea (90-N), and no fertilization (control) at planting of winter wheat. Fluxes of N2O were measured by closed chamber methods after soil incorporation of cowpea in autumn (October–November) and harvesting of winter wheat in summer (June–August). Growth and yields of winter wheat and N concentrations in grain and straw were also measured. Cowpea produced 9.5 Mg ha−1 shoot biomass with 253 kg N ha−1 at termination. Although soil moisture was favorable for denitrification after soil incorporation of cowpea biomass, low concentrations of soil mineral N restricted emissions of N2O from cowpea treatment. However, increased concentrations of soil mineral N and large rainfall-induced emissions were recorded from the cowpea treatment during summer. Growth of winter wheat, yield, and grain N concentrations were lowest in response to cowpea treatment and highest in 90-N treatment. In conclusion, late terminated cowpea may reduce yield of winter wheat and increase emissions of N2O outside of wheat growing seasons due to poor synchronization of N mineralization from cowpea biomass with N-demand of winter wheat.

Information

Type
Research Article
Copyright
© Cambridge University Press 2019

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