No-till annual wheat increases plant productivity, soil microbial biomass, and soil carbon stabilization relative to intermediate wheatgrass in a Mediterranean climate

Authors: Taylor, Kalyn; NELSEN, TAYLOR - University Of California, Davis; SCOW, KATE - University Of California, Davis; LUNDY, MARK - University Of California, Davis

Submitted to: Soil and Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2023
Publication Date: 9/28/2023
Citation: Taylor, K.M., Nelsen, T.S., Scow, K.M., Lundy, M.E. 2023. No-till annual wheat increases plant productivity, soil microbial biomass, and soil carbon stabilization relative to intermediate wheatgrass in a Mediterranean climate. Soil and Tillage Research. 235. Article 105874. https://doi.org/10.1016/j.still.2023.105874.
DOI: https://doi.org/10.1016/j.still.2023.105874

Interpretive Summary: As interest in the production of novel perennial grain crops increases, it is critical to quantify differences in aboveground biomass productivity and soil carbon stabilization potential between annual and perennial grain crops, and to understand the factors determining these relationships. In this study, we measured the effects of crop type and nitrogen fertilization on aboveground biomass production, soil microbial biomass, and soil carbon while controlling for the effect of tillage in annual and perennial grain crops in a Mediterranean climate. Aboveground biomass and associated soil samples from tilled annual wheat, no-till annual wheat, and intermediate wheatgrass [Kernza ® (Thinopyrum intermedium)] (IWG) were collected annually across three years under various N fertilization rates. The no-till annual wheat treatment achieved greater soil microbial biomass and significantly higher soil carbon stabilization potential in the top 30 cm of soil than the IWG and tilled annual wheat systems by matching tilled annual wheat in plant vigor and IWG in lack of soil disturbance. Thus, our results suggest that no-till annual wheat is better suited than tilled annual wheat or IWG to increase soil microbial biomass and soil carbon stabilization in shallow soil, while still maintaining stable aboveground biomass yields over time in a Mediterranean climate.

Technical Abstract: As interest in the production of perennial grain crops increases, it is critical to quantify differences in aboveground biomass (AGB) productivity and soil carbon stabilization potential between annual and perennial grain crops, and to understand the factors determining these relationships. This study measured the effects of crop type and nitrogen (N) fertilization on AGB, soil microbial biomass, and soil carbon while controlling for the effect of tillage in annual and perennial grain crops in a Mediterranean climate. AGB and associated soil samples from tilled annual wheat (Triticum aestivum), no-till annual wheat, and intermediate wheatgrass [Kernza ® (Thinopyrum intermedium)] (IWG) were collected annually across three years under various N fertilization rates. We quantified AGB yields, soil microbial biomass (via phospholipid fatty acid analysis), permanganate oxidizable carbon (POXC) and mineralizable soil carbon (MinC). Across N rates and years, IWG yielded 25% less AGB than tilled and no-till annual wheat (p =.001). The lack of soil disturbance in no-till wheat and IWG contributed foremost to greater microbial biomass abundance in the topsoil by year three of the experiment (p < 0.1), while crop type and the associated AGB productivity had the greatest influence on whether microbial communities trended toward stabilizing versus mineralizing soil organic carbon. More specifically, higher carbon stabilization processes were primarily driven by the increased plant productivity of tilled and no-till annual wheat compared to IWG. Within the annual wheat systems, lack of tillage also contributed to soil carbon stabilization, but primarily in the topsoil. Overall, the no-till annual wheat treatment achieved 20-36% greater soil microbial biomass and significantly higher soil carbon stabilization potential (p = 0.04) in the top 30 cm of soil than the IWG and tilled annual wheat systems by matching tilled annual wheat in plant vigor and IWG in lack of soil disturbance. Contrary to our original hypothesis, our results suggest that no-till annual wheat is better suited than tilled annual wheat or IWG to increase soil microbial biomass and soil carbon stabilization in shallow soil, while still maintaining stable aboveground biomass yields over time in a Mediterranean climate.