Abstract
Nitrogen (N) fertilizers can potentially alter spatial distribution of soil organic carbon (SOC) and total nitrogen (TN) concentrations in croplands such as switchgrass (SG: Panicum virgatum L.) and gamagrass (GG: Tripsacum dactyloides L.), but it remains unclear whether these effects are the same between crops and under different rates of fertilization. 13C and 15N are two important proxy measures of soil biogeochemistry, but they were rarely examined as to their spatial distributions in soil. Based on a three-year long fertilization experiment in Middle Tennessee, USA, the top mineral horizon soils (0–15 cm) were collected using a spatially explicit design within two 15-m2 plots under three fertilization treatments in SG and GG croplands. A total of 288 samples were collected based on 12 plots and 24 samples in each plot. The fertilization treatments were no N input (NN), low N input (LN: 84 kg N ha−1 in urea) and high N input (HN: 168 kg N ha−1 in urea). The SOC, TN, SOC/TN (C: N), δ13C and δ15N were quantified and their within-plot variations and spatial distributions were achieved via descriptive and geostatistical methods. Results showed that SG generally displayed 10~120% higher plot-level variations in all variables than GG, and the plot-level variations were 20~77% higher in NN plots than LN and HN plots in SG but they were comparable in unfertilized and fertilized plots in GG. Relative to NN, LN and HN showed more significant surface trends and spatial structures in SOC and TN in both croplands, and the fertilization effect appeared more pronounced in SG. Spatial patterns in C: N, δ13C and δ15N were comparable among different fertilization treatments in both croplands. The descending within-plot variations were also identified among variables (SOC > TN > δ15N > C: N > δ13C). This study demonstrated that N fertilizations generally reduced the plot-level variance and simultaneously re-established spatial structures of SOC and TN in bioenergy croplands, which little varied with fertilization rate but was more responsive in switchgrass cropland.
Original language | English |
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Article number | 1211 |
Journal | Scientific Reports |
Volume | 10 |
Issue number | 1 |
DOIs | |
State | Published - Dec 1 2020 |
Funding
This study was supported by funding awarded to JL from a US National Science Foundation (NSF) DEB HBCU UP EiR Grant (No. 1900885), US Department of Agriculture 1890 Faculty Research Sabbatical Program (58-3098-9-005) and Evans-Allen Grant (No. 1017802). Funding for MAM was provided by the US Department of Energy (DOE) Office of Biological and Environmental Research through the Terrestrial Ecosystem Science Scientific Focus Area at Oak Ridge National Laboratory (ORNL). ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US DOE. We thank staff members at the TSU’s Main Campus AREC in Nashville, Tennessee for their assistance. We appreciate the anonymous reviewers for their constructive comments and suggestions.
Funders | Funder number |
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National Science Foundation | 1900885 |
U.S. Department of Energy | |
U.S. Department of Agriculture | 58-3098-9-005, 1017802 |
Biological and Environmental Research | |
Oak Ridge National Laboratory | DE-AC05-00OR22725 |