Agricultural management legacy effects on switchgrass growth and soil carbon gains

These datasets are part of the manuscript "Agricultural management
legacy effects on switchgrass growth and soil carbon gains" in which
we observed the impact of historic tillage management and historic and
continued N fertilization on switchgrass growth and soil C gains. In this
study, we hypothesized that the inconsistencies in soil organic
carbon (SOC) accrual by switchgrass might be due, in part, to differences
in prior land management among the systems subsequently planted to
switchgrass. To test this hypothesis, we measured SOC and other soil
properties, root biomass, and switchgrass growth in an experimental site
with a 30-year history of contrasting tillage and N-fertilization
treatments, seven years after switchgrass establishment. We determined
switchgrass’s monthly gross primary production (GPP) for six consecutive
years and conducted deep soil sampling. Nitrogen fertilization expectedly
stimulated switchgrass growth, however, a tendency for better plant growth
was also observed under unfertilized settings in the former no-till soil.
In topsoil, SOC significantly increased from 2007 to 2023 in fertilized
treatments of both tillage histories, with the greatest increase observed
in fertilized no-till. Fertilized no-till also had the highest particulate
organic matter content in the topsoil, with no differences among the
treatments observed in deeper soil layers. However, regardless of
fertilization, the tillage history had a strong effect on stratification
with depth of SOC, total N, and microbial biomass C. Results suggested
that historic and ongoing N fertilization had a substantial impact on
switchgrass growth and soil characteristics, while tillage legacy had a
much weaker, but still discernible, effect.