@article{carvalho_howard_crozier_johnson_sayde_chinn_godfrey iii_heitman_2024, title={Water use and radiation balance of miscanthus and corn on marginal land in the coastal plain region of North Carolina}, volume={16}, ISSN={["1757-1707"]}, DOI={10.1111/gcbb.13182}, abstractNote={Abstract Miscanthus is a perennial grass that can yield substantial amounts of biomass in land areas considered marginal. In the Coastal Plain region of North Carolina, marginal lands are typically located in coarse‐textured soils with low nutrient retention and water‐holding capacity, and high erosivity potential. Little is known about miscanthus water use under these conditions. We conducted a study to better understand the efficiency with which miscanthus uses natural resources such as water and radiant energy to produce harvestable dry biomass in comparison to corn, a typical commodity crop grown in the region. We hypothesized that under non‐limiting soil water conditions, miscanthus would have greater available energy and water use rates owing to its greater leaf area, thus leading to greater agronomic yields. Conversely, these effects would be negated under drought conditions. Our measurements showed that miscanthus intercepted more radiant energy than corn, which led to greater albedo (by 0.05), lower net radiation (by 4% or 0.4 MJ m −2 day −1 ), and lower soil heat flux (by 69% or 1.0 MJ m −2 day −1 ) than corn on average. Consequently, miscanthus had greater available energy (by 7% or 0.6 MJ m −2 day −1 ) and water use rates (by 14% or 0.5 mm day −1 ) than corn throughout the growing season on average, which partially confirmed our hypothesis. Greater water use rates and radiation interception by miscanthus did not translate to greater water‐use (1.5 g kg −1 vs. 1.6 g kg −1 ) and radiation‐use (0.9 g MJ −1 vs. 1.1 g MJ −1 ) efficiencies than corn. Compared to literature values, our data indicated that water and radiation availability were not limiting at our study site. Thus, it is likely that marginal land features present at the Coastal Plain region such as low soil fertility and high air temperatures throughout the growing season may constrain agronomic yields even if soil water and radiant energy are non‐limiting.}, number={8}, journal={GLOBAL CHANGE BIOLOGY BIOENERGY}, author={Carvalho, Henrique D. R. and Howard, Adam M. and Crozier, Carl R. and Johnson, Amy M. and Sayde, Chadi and Chinn, Mari S. and Godfrey III, Edward E. and Heitman, Joshua L.}, year={2024}, month={Aug} }
 @article{carvalho_howard_amoozegar_crozier_johnson_heitman_2023, title={Water vapor transport through bioenergy grass residues and its effects on soil water evaporation}, volume={10}, ISSN={["1539-1663"]}, url={https://doi.org/10.1002/vzj2.20282}, DOI={10.1002/vzj2.20282}, abstractNote={AbstractMiscanthus is a productive perennial grass that is suitable as a bioenergy crop in “marginal” lands (e.g., eroded soils) with low water holding capacity. However, little is known about the impact of miscanthus residues on vapor transport and soil water budgets. Laboratory experiments were conducted to measure the vapor conductance through miscanthus residues and its effect on soil water evaporation. The ranges for the length, width, and thickness of residue elements were 0.5–9.0, 0.1–0.5, and 0.1–0.5 cm, respectively. Average residue areal, bulk, and skeletal densities were 0.88 kg m−2, 24 kg m−3, and 1006 kg m−3, respectively, giving a porosity of 0.98 m3 m−3. A power function described the decrease in conductance with increasing residue load. The corresponding conductance for a residue load of 0.88 kg m−2 was 1.6 mm s−1. During the first days of a 60‐day drying experiment, cumulative evaporation showed logarithmic decay with increasing residue load. Conversely, cumulative evaporation during the last days of the study showed little difference between treatments. Measurements indicated that there is a “critical” residue load (∼1.0 kg m−2) beyond which evaporation no longer decreases appreciably when the soil is under the stage 1 evaporation regime. Results suggest that soil water conservation in marginal lands may be accomplished by maintaining moderate amounts of bioenergy grass residue covering the soil. Determining “critical” loads for different residue types is a knowledge gap that merits further research.}, journal={VADOSE ZONE JOURNAL}, author={Carvalho, Henrique D. R. and Howard, Adam M. and Amoozegar, Aziz and Crozier, Carl R. and Johnson, Amy M. and Heitman, Joshua L.}, year={2023}, month={Oct} }
 @article{crozier_carvalho_johnson_chinn_heitman_2021, title={Appropriate "marginal" farmlands for second-generation biofuel crops in North Carolina}, volume={6}, ISSN={["2471-9625"]}, DOI={10.1002/ael2.20041}, abstractNote={AbstractCurrent research on bioenergy crops shows that perennial grasses can yield substantial amounts of dry biomass with relatively low inputs of water and fertilizer. In order to minimize competition with food production, it has been suggested that bioenergy crops could be directed to land areas less suitable for commodity crops, commonly referred to as “marginal” lands. These are land units with inherent limitations to vegetative growth and production, which may be due to several factors (soil physical and chemical properties, climatic conditions, etc.). However the term “marginal” is an adjective with imprecise meaning, and objective criteria for determining “marginal” lands for siting bioenergy crops are necessary. Here we propose that such criteria may be based on soil survey classifications and realistic yield estimates, and we show an example of its use to justify site selection for bioenergy crops in different regions of North Carolina.}, number={1}, journal={AGRICULTURAL & ENVIRONMENTAL LETTERS}, author={Crozier, C. R. and Carvalho, H. D. R. and Johnson, A. and Chinn, M. and Heitman, J. L.}, year={2021} }
 @article{kranz_mclaughlin_johnson_miller_heitman_2020, title={The effects of compost incorporation on soil physical properties in urban soils – A concise review}, volume={261}, ISSN={0301-4797}, url={http://dx.doi.org/10.1016/j.jenvman.2020.110209}, DOI={10.1016/j.jenvman.2020.110209}, abstractNote={Incorporation of compost into soil can significantly alter soil physical properties, nutrient dynamics, and vegetation establishment. Strategic compost application to disturbed, degraded urban soil may provide benefits to soil properties. This review compared twenty-five peer-reviewed studies that evaluated changes in soil bulk density, infiltration rate, hydraulic conductivity, and water retention where compost was incorporated into urban soils. A wide range of compost rates and incorporation depths were evaluated in these studies across many soil types. Compost incorporation generally reduced bulk density, enhanced infiltration and hydraulic conductivity, and increased water content and plant available water, compared to unamended controls. In the four studies on runoff water quality, compost incorporation often resulted in higher initial nutrient content in runoff water, but also enhanced grass growth and reduced sediment loss. Few studies evaluated multiple compost application rates or incorporation depths, and the ways in which compost application rates were reported varied widely between studies making it difficult to directly compare them. Four studies investigated the long-term effects of compost incorporation, and there was no clear pattern of why some soils display enhanced physical properties over time and others do not. Compost was largely reported to have a positive effect on degraded urban soils. Little research has focused on the longevity of compost in urban soils after one application, and thus, this would be a valuable topic of further investigation.}, journal={Journal of Environmental Management}, publisher={Elsevier BV}, author={Kranz, Christina N. and McLaughlin, Richard A. and Johnson, Amy and Miller, Grady and Heitman, Joshua L.}, year={2020}, month={May}, pages={110209} }
 @article{lindsey_johnson_kim_jackson_labbé_2013, title={Monitoring switchgrass composition to optimize harvesting periods for bioenergy and value-added products}, volume={56}, ISSN={0961-9534}, url={http://dx.doi.org/10.1016/J.BIOMBIOE.2013.04.023}, DOI={10.1016/J.BIOMBIOE.2013.04.023}, abstractNote={Switchgrass (Panicum virgatum) is a perennial grass that has emerged as an ideal candidate for production of biofuel and value-added co-products. One of the primary requirements for the successful manufacturing of these switchgrass-derived bioproducts is to produce a consistent feedstock with reliable and adequate amounts of the substrate constituent needed. For example, the biofuels industry requires a fast-growing energy crop with higher cellulose content and lower inhibitors found in secondary constituents. Other industries would profit from higher lignin content for products such as carbon fibers, or higher water and ethanol-soluble extracts containing compounds of interest. Two switchgrass field plots in eastern Tennessee were monitored over a period of six months, including before and after traditional harvesting times for the biorefinery. Characterization of the biomass and its constituents, such as water and ethanol extracts, cellulose, hemicelluloses, lignin, and ash, was performed to examine chemical changes in switchgrass that occurred prior to, during, and after traditional harvesting times used in a biorefinery setting. Total carbohydrate (65.6–66.7 wt%) and lignin (21.7–23.2 wt%) content was found to peak in January. Extractives content was at a maximum in early harvests at 15.9–16.6 wt% and decreased to 5.5–5.8 wt% in February. An inverse relationship exists between the extractives and lignin content (R2 = 0.94). Nonstructural soluble sugars peaked in early October with 5.1 wt% of the switchgrass composition. Remobilization efficiencies of K, Mg, P, and Fe increased with time, indicating conservation of soil nutrients if harvests were completed in late winter.}, journal={Biomass and Bioenergy}, publisher={Elsevier BV}, author={Lindsey, Kline and Johnson, Amy and Kim, Pyoungchung and Jackson, Samuel and Labbé, Nicole}, year={2013}, month={Sep}, pages={29–37} }
 @article{kim_johnson_essington_radosevich_kwon_lee_rials_labbé_2013, title={Effect of pH on surface characteristics of switchgrass-derived biochars produced by fast pyrolysis}, volume={90}, ISSN={0045-6535}, url={http://dx.doi.org/10.1016/j.chemosphere.2012.11.021}, DOI={10.1016/j.chemosphere.2012.11.021}, abstractNote={Surface properties of switchgrass-derived biochars produced at fast pyrolysis temperatures of 450, 600 and 800 °C were characterized at different solution pHs in order to determine the structural and chemical changes of artificially-weathered biochars when incorporated into soil. As biochars were acidified from pH 7 to 3, crystalline minerals dissolved slowly releasing nutrients; however, residual minerals were still detected in biochars produced at higher pyrolysis temperatures after pH treatment. Moreover, the amount of exchangeable bases and other inorganic compounds released from the biochars increased when pH decreased. As minerals dissolved from the biochars, total surface area and pore volume were found to increase. Surface functional groups and water vapor adsorption capacity at 0.8 P/Po also increased, whereas the potential CEC of biochars decreased due to the replacement of exchangeable sites by hydrogen ion. Therefore, during the aging process, it is predicted that soil-incorporated biochars will slowly release nutrients with changes in surface functionality and porosity, which are expected to enhance water holding capacity of soil and provide a beneficial habitat for microbial colonization.}, number={10}, journal={Chemosphere}, publisher={Elsevier BV}, author={Kim, Pyoungchung and Johnson, Amy M. and Essington, Michael E. and Radosevich, Mark and Kwon, Woo-Tech and Lee, Seung-Hwan and Rials, Timothy G. and Labbé, Nicole}, year={2013}, month={Mar}, pages={2623–2630} }
 @article{cai_johnson_schwartz_moore_kulp_2011, title={Response of Soil Water Chemistry to Simulated Changes in Acid Deposition in the Great Smoky Mountains}, volume={137}, ISSN={0733-9372 1943-7870}, url={http://dx.doi.org/10.1061/(ASCE)EE.1943-7870.0000354}, DOI={10.1061/(ASCE)EE.1943-7870.0000354}, abstractNote={Watershed recovery from acidic deposition, such as the Noland Divide Watershed in the Great Smoky Mountains National Park, is difficult to predict because of complex biogeochemical processes exhibited in soils. Laboratory soil columns and in situ pan lysimeters were used to investigate soil solution response to simulated reductions in acid deposition. Controlling for influent SO42-, NO3-, and NH4+ concentrations in the column experiments, effluent pH declined similarly to 4.4 among five experimental scenarios from an initial pH of approximately 4.7 and 6.1. Influent-effluent chemical comparisons suggest nitrification and/or SO42- desorption controls effluent pH. Sulfate adsorption occurred when SO42- influent was greater than 25  μmol L-1 and desorption occurred below 15  μmol L-1, which would equate to approximately a 61% reduction in current SO42- deposition levels. Base cation depletion occurred in column experiments, in which 64–60  μmol L-1 Ca2+ and 24–27  μmol L-1 Mg2+ reductions were measured. Cati...}, number={7}, journal={Journal of Environmental Engineering}, publisher={American Society of Civil Engineers (ASCE)}, author={Cai, Meijun and Johnson, Amy M. and Schwartz, John S. and Moore, Stephen E. and Kulp, Matt A.}, year={2011}, month={Jul}, pages={617–628} }
 @article{cai_johnson_schwartz_moore_kulp_2011, title={Soil Acid-Base Chemistry of a High-Elevation Forest Watershed in the Great Smoky Mountains National Park: Influence of Acidic Deposition}, volume={223}, ISSN={0049-6979 1573-2932}, url={http://dx.doi.org/10.1007/S11270-011-0858-X}, DOI={10.1007/S11270-011-0858-X}, number={1}, journal={Water, Air, & Soil Pollution}, publisher={Springer Science and Business Media LLC}, author={Cai, Meijun and Johnson, Amy M. and Schwartz, John S. and Moore, Steve E. and Kulp, Matt A.}, year={2011}, month={Jun}, pages={289–303} }
 @article{kim_johnson_edmunds_radosevich_vogt_rials_labbé_2011, title={Surface Functionality and Carbon Structures in Lignocellulosic-Derived Biochars Produced by Fast Pyrolysis}, volume={25}, ISSN={0887-0624 1520-5029}, url={http://dx.doi.org/10.1021/ef200915s}, DOI={10.1021/ef200915s}, abstractNote={Switchgrass- and pine wood-derived biochars produced by fast pyrolysis were characterized to estimate the degree of thermochemical transformation and to assess their potential use as a soil amendment and to sequester carbon. The feedstocks were pyrolyzed to biochars in an auger reactor at 450, 600, and 800 °C with a residence time of 30 s. Ash contents of switchgrass and pine wood biochars varied from 13 to 22% and from 1.3 to 5.2%, respectively. Nutrients, such as N, P, K, S, Mg, and Ca, in switchgrass biochars ranged from 0.16 to 1.77%. Under combustion conditions, switchgrass chars were decomposed at lower temperatures than pine wood biochars because of the structural differences between the two feedstocks. Principal component analysis of the Fourier transform infrared (FTIR) spectra allowed for the discrimination of all biochars by significant contributions of cellulose-derived functionality at low pyrolysis temperatures, while the same analysis of the Raman spectra presented apparent separation of al...}, number={10}, journal={Energy & Fuels}, publisher={American Chemical Society (ACS)}, author={Kim, Pyoungchung and Johnson, Amy and Edmunds, Charles W. and Radosevich, Mark and Vogt, Frank and Rials, Timothy G. and Labbé, Nicole}, year={2011}, month={Oct}, pages={4693–4703} }
 @article{johnson_osmond_hodges_2005, title={Predicted impact and evaluation of North Carolina's phosphorus indexing tool}, volume={34}, ISSN={["1537-2537"]}, DOI={10.2134/jeq2005.0020}, abstractNote={ABSTRACTIncreased concern about potential losses of phosphorus (P) from agricultural fields receiving animal waste has resulted in the implementation of new state and federal regulations related to nutrient management. In response to strengthened nutrient management standards that require consideration of P, North Carolina has developed a site‐specific P indexing system called the Phosphorus Loss Assessment Tool (PLAT) to predict relative amounts of potential P loss from agricultural fields. The purpose of this study was to apply the PLAT index on farms throughout North Carolina in an attempt to predict the percentage and types of farms that will be forced to change management practices due to implementation of new regulations. Sites from all 100 counties were sampled, with the number of samples taken from each county depending on the proportion of the state's agricultural land that occurs in that county. Results showed that approximately 8% of producers in the state will be required to apply animal waste or inorganic fertilizer on a P rather than nitrogen basis, with the percentage increasing for farmers who apply animal waste (approximately 27%). The PLAT index predicted the greatest amounts of P loss from sites in the Coastal Plain region of North Carolina and from sites receiving poultry waste. Loss of dissolved P through surface runoff tended to be greater than other loss pathways and presents an area of concern as no best management practices (BMPs) currently exist for the reduction of in‐field dissolved P. The PLAT index predicted the areas in the state that are known to be disproportionately vulnerable to P loss due to histories of high P applications, high densities of animal units, or soil type and landscapes that are most susceptible to P loss.}, number={5}, journal={JOURNAL OF ENVIRONMENTAL QUALITY}, author={Johnson, AM and Osmond, DL and Hodges, SC}, year={2005}, pages={1801–1810} }
 @article{johnson_hoyt_1999, title={Changes to the soil environment under conservation tillage}, volume={9}, number={3}, journal={HortTechnology}, author={Johnson, A. M. and Hoyt, G. D.}, year={1999}, pages={380} }