@article{meeks_cabrera_thapa_noor_mirsky_reberg-horton_2023, title={Biochemical composition of cover crop residues determines water retention and rewetting characteristics}, volume={9}, ISSN={["1435-0645"]}, url={https://doi.org/10.1002/agj2.21451}, DOI={10.1002/agj2.21451}, abstractNote={When cover crop residues are left on the soil surface, their decompositionThis article is protected by copyright. All rights reserved}, journal={AGRONOMY JOURNAL}, author={Meeks, Carley and Cabrera, Miguel and Thapa, Resham and Noor, Nadia and Mirsky, Steven and Reberg-Horton, Chris}, year={2023}, month={Sep} }
 @article{thapa_cabrera_schomberg_reberg-horton_poffenbarger_mirsky_2023, title={Chemical differences in cover crop residue quality are maintained through litter decay}, volume={18}, ISSN={["1932-6203"]}, url={https://doi.org/10.1371/journal.pone.0289352}, DOI={10.1371/journal.pone.0289352}, abstractNote={As plant litter decomposes, its mass exponentially decreases until it reaches a non-zero asymptote. However, decomposition rates vary considerably among litter types as a function of their overall quality (i.e., carbon:nitrogen (C:N) ratio and litter chemistry). We investigated the effects of hairy vetch (HV: Vicia villosa Roth):cereal rye (RYE: Secale cereale L.) biomass proportions with or without broadcasted poultry manure on overall litter quality before and during decomposition. As HV biomass proportions increased from 0 to 100%, the relative susceptibility of HV:RYE mixtures to microbial decomposition increased due to: (i) decrease in the initial C:N ratio (87:1 to 10:1 in 2012 and 67:1 to 9:1 in 2013), (ii) increase in the non-structural labile carbohydrates (33 to 61% across years), and (iii) decrease in the structural holo-cellulose (59 to 33% across years) and lignin (8 to 6% across years) fractions. Broadcasted poultry manure decreased the overall initial quality of HV-dominated litters and increased the overall initial quality of RYE-dominated litters. Across all HV:RYE biomass proportions with or without poultry manure, chemical changes during litter decay were related to proportional mass loss. Therefore, the relative decrease in carbohydrates and the concomitant increase in holo-cellulose and lignin fractions were more pronounced for fast decomposing litter types, i.e., litters dominated by HV rather than RYE. While our results suggest possible convergence of litter C:N ratios, initial differences in litter chemistry neither converged nor diverged. Therefore, we conclude that the initial chemistry of litter before decomposition exerts a strong control on its chemical composition throughout the decay continuum.}, number={7}, journal={PLOS ONE}, author={Thapa, Resham and Cabrera, Miguel and Schomberg, Harry H. and Reberg-Horton, Chris and Poffenbarger, Hanna and Mirsky, Steven B.}, editor={Villalobos, Luis AlonsoEditor}, year={2023}, month={Jul} }
 @article{mirsky_davis_poffenbarger_cavigelli_maul_schomberg_spargo_thapa_2023, title={Managing cover crop C:N ratio and subsurface-banded poultry litter rate for optimal corn yields}, ISSN={["1435-0645"]}, DOI={10.1002/agj2.21369}, abstractNote={Abstract Cover crops can be used to provide some of the nitrogen (N) needs of a cash crop to complement mineral fertilizers or manure, but there has yet been limited work to describe corn ( Zea mays L.) yield as a function of cover crop quality and N inputs. We investigated the response of corn yield to gradients of both preceding cover crop C:N ratio and poultry litter (PL) application rates in Beltsville, MD during 2012–2014. To achieve different C:N ratios of the cover crops, hairy vetch ( Vicia villosa Roth. "Groff") and cereal rye ( Secale cereale L. "Aroostook") were seeded in a replacement series of six seeding rate proportions, resulting in shoot C:N ratios of 9.2:1 to 152:1 across years. For each hairy vetch/cereal rye sown proportions, PL was side‐dressed at corn V5–V8 stage in subsurface bands (SSB) at four targeted rates: Zero, P‐based (67 kg plant available nitrogen [PAN] ha −1 ), N‐based (135 kg PAN ha −1 ), and excess N and P (269 kg PAN ha −1 ). We found that corn yield followed a linear‐plateau relationship across these two dimensions. Within the linear region, each unit increase in log‐scaled cover crop C:N ratio resulted in a yield decrease of 2.56 ± 0.26 Mg ha −1 at a given rate of SSB PL. To optimize corn yields, we describe a model where each unit increase in log‐scaled cover crop C:N ratio required an additional 45.9 ± 6.22 kg PAN ha −1 from SSB PL. Yields following winter fallow were typically intermediate to the range of yields observed following the gradient of cover crop C:N ratios. We did not find significant differences in corn yield responses when comparing SSB PL to at‐planting incorporated or broadcast PL; we also found no significant differences between SSB PL and surface‐banded urea ammonium nitrate. Taken together, our approach of modeling yield response across two dimensions can be widely used to guide adaptive N management in subsequent cash crops following winter cover crops, thereby balancing both economic and environmental objectives in cover crop‐based cropping systems.}, journal={AGRONOMY JOURNAL}, author={Mirsky, Steven B. and Davis, Brian W. and Poffenbarger, Hanna and Cavigelli, Michel A. and Maul, Jude E. and Schomberg, Harry and Spargo, John T. and Thapa, Resham}, year={2023}, month={Jun} }
 @article{singh_thapa_kukal_irmak_mirsky_jhala_2022, title={Effect of water stress on weed germination, growth characteristics, and seed production: a global meta-analysis}, ISSN={["1550-2759"]}, DOI={10.1017/wsc.2022.59}, abstractNote={Abstract Weeds compete with crops for soil moisture, along with other resources, which can impact the germination, growth, and seed production of weeds; however, this impact has not been systematically recorded and synthesized across diverse studies. To address this knowledge gap, a global meta-analysis was conducted using 1,196 paired observations from 86 published articles assessing the effect of water stress on weed germination, growth characteristics, and seed production. These studies were conducted and published during 1970 through 2020 across four continents (Asia, Australia, Europe, and North America). Imposed water stress was expressed as solution osmotic potential (ψsolution), soil water potential (ψsoil), or soil moisture as percent field capacity. Meta-analysis revealed that water stress inhibits weed germination, growth, and seed production, and the quantitative response intensified with increasing water stress. A ψsolution greater than –0.8 MPa completely inhibits germination of both grass and broadleaf weeds. A ψsolution from –0.09 to –0.32 MPa reduces weed germination by 50% compared with the unstressed condition. Moderate soil water stress, equivalent to 30% to 60% field capacity, inhibits growth characteristics (branches or tillers per plant, leaf area, leaves per plant, plant height, root, and shoot biomass) by 33% and weed seed production by 50%. Severe soil water stress, below 30% field capacity, inhibits weed growth by 51% and seed production by 88%. Although water stress inhibits weed growth, it does not entirely suppress the ability to germinate, grow, and produce seeds, resulting in weed seedbank accumulation. This creates management challenges for producers, because weed seeds can survive in the soil for many years, depending on weed species and environmental conditions. Quantitative information compiled in this meta-analysis can be instrumental to model the weeds' multidimensional responses to water stress and designing integrated weed management strategies for reducing the weed seedbank.}, journal={WEED SCIENCE}, author={Singh, Mandeep and Thapa, Resham and Kukal, Meetpal Singh and Irmak, Suat and Mirsky, Steven and Jhala, Amit J.}, year={2022}, month={Oct} }
 @article{thapa_cabrera_reberg-horton_dann_balkcom_fleisher_gaskin_hitchcock_poncet_schomberg_et al._2022, title={Modeling surface residue decomposition and N release using the Cover Crop Nitrogen Calculator (CC-NCALC)}, volume={8}, ISSN={["1573-0867"]}, DOI={10.1007/s10705-022-10223-3}, journal={NUTRIENT CYCLING IN AGROECOSYSTEMS}, author={Thapa, Resham and Cabrera, Miguel and Reberg-Horton, Chris and Dann, Carson and Balkcom, Kip S. and Fleisher, David and Gaskin, Julia and Hitchcock, Rick and Poncet, Aurelie and Schomberg, Harry H. and et al.}, year={2022}, month={Aug} }