Location: Agricultural Systems ResearchTitle: Soil total carbon and nitrogen under long-term perennial bioenergy crops receiving various nitrogen fertilization rates
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/14/2023
Publication Date: 8/1/2023
Citation: Sainju, U.M., Allen, B.L., Lenssen, A.W. 2023. Soil total carbon and nitrogen under long-term perennial bioenergy crops receiving various nitrogen fertilization rates. Agronomy Journal. 2023:1-11. https://doi.org/10.1002/agj2.21422.
Interpretive Summary: Increasing levels of carbon dioxide in the atmosphere are of worldwide concern. Agricultural soils can be either a source or sink for atmospheric carbon depending on agricultural production practices. Perennial bioenergy crops have the potential to sequester carbon in soils because they produce more root biomass and lead to less soil disturbance than annual crops. Nitrogen fertilization rate of perennial grasses may impact the amount of biomass produced and its N content thus affecting both soil carbon levels and nutrient cycling. More information about the effects of these management factors will contribute to a better understanding of how agroecosystems can help mitigate climate change. ARS researchers at Sidney, MT in collaboration with Iowa State University conducted a 10-year study on carbon and nitrogen sequestration potentials of perennial bioenegy crops with various nitrogen fertilization rates and reported that intermediate wheatgrass sequestered more carbon in the whole soil profile (to a depth of 48 inches) than either smooth bromegrass or swithgrass in the northern Great Plains. Nitrogen fertilization rate had no effect on soil carbon and nitrogen. Perennial bioenergy crops also sequestered more carbon and nitrogen in the surface soil layer than an annual spring wheat crop. Producers in semi-arid areas similar to the northern Great Plains can benefit from planting perennial grasses such as intermediate wheatgrass as a result of increased carbon sequestration and potential carbon credits.
Technical Abstract: Perennial crops may sequester greater soil C and N than annual crops due to increased root biomass production, but the potential of long-term cultivation of perennial bioenergy crops receiving various N fertilization rates in sequestering C and N needs further exploration. Soil samples (0-120 cm) collected from 2009 to 2019 under perennial bioenergy crops receiving various N fertilization rates and an annual crop were analyzed for soil total C (STC) and N (STN) in the northern Great Plains, USA. Perennial bioenergy crops were intermediate wheatgrass (Thinopyrum intermedium [Host] Barkworth and Dewey, IW), smooth bromegrass (Bromus inermis L., SB), and switchgrass (Panicum virgatum L., SG); N fertilization rates were 0, 28, 56, and 84 kg N ha-1, and annual crop was spring wheat (Triticum aestivum, L., WH). The STC increased, but STN decreased with soil depth, regardless of treatments and years. At 0-120 cm, IW sequestered C at 10.6 Mg C ha-1 yr-1 compared with 5.4-6.8 Mg C ha-1 yr-1 for SB and SG from 2009 to 2019. Nitrogen fertilization rate had limited effect on STC and STN. At 0-30 cm, STC was 2.0-5.4 Mg C ha-1 greater and STN 0.10-0.24 Mg N ha-1 greater with perennial bioenergy crops than WH. Long-term cultivation of IW can sequester more C in the soil to a greater depth than SB and SG and perennial bioenergy crops can sequester more C and N at the surface layers than an annual crop in the semiarid region of the US northern Great Plains.