Bioenergy carbon capture and storage (BECCS) systems can serve as decarbonization pathways for climate mitigation. Perennial grasses are a promising second-generation lignocellulosic bioenergy feedstock, but optimizing their sustainability, productivity, and climate mitigation potential requires an evaluation of how nitrogen (N) fertilizer strategies interact with greenhouse gas (GHG) and soil organic carbon (SOC) dynamics. Further, crop and fertilizer choice can affect the soil microbiome which is critical to soil organic matter turnover, nutrient cycling, and sustaining crop productivity but these feedbacks are poorly understood due to the paucity of data from agroecosystems. Here, we examine the climate mitigation potential and soil microbiome response to establishing two functionally different perennial grasses, switchgrass (Panicum virgatum, C4), and tall wheatgrass (Thinopyrum ponticum, C3), in a cool semi-arid agroecosystem under two fertilizer applications, a novel cyanobacterial biofertilizer (CBF) and urea. Finally, we examine shifts in soil microbial composition resulting from crop establishment and fertilizer regime. We find that in contrast to the C4 crop, the C3 crop achieved 98% greater productivity and had a higher N use efficiency when fertilized and the CBF produced the same biomass enhancement as urea. Non-CO2 greenhouse gas fluxes across all treatments were low and we observed a three-year net loss of SOC under the C4 crop and a net increase under the C3 crop at a 0-30 cm soil depth regardless of fertilization. Further, we detected crop-specific changes in the soil microbiome, including an increased relative abundance of arbuscular mycorrhizal fungi under the C3, and potentially pathogenic fungi in the C4 grass. Taken together, these findings highlight the potential of CBF-fertilized C3 crops as a second-generation bioenergy feedstock in semiarid regions as a part of a climate mitigation strategy.

The dataset was collected and compiled between 2017 and 2020. Soil carbon and nitrogen data from 2017 were collected at two depths (0-15cm) and (15-30cm). Soil carbon and nitrogen data from 2020 were collected at three depths (0-5cm), (5-15cm), and (15-30cm). A weighted average was used to compare the three-year change. Greenhouse gas flux data (CO2, CH4, and N2O) were collected in 2020 acoss multiple sampling periods from March to October using a Picarro G2508 analyzer. Both aboveground biomass (equal mix of stem + leaf + infloresence) data are from two perennial grasses, switchgrass and tall wheatgrass, that were harvested in September 2020.  Root biomass and chemistry data are from the top 15 cm of the soil of both switchgrass and tall wheatgrass.

The data were compiled in microsoft excel and processed in R using packages cited in the manuscript.