@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={AbstractCover 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{thapa_tully_reberg-horton_cabrera_davis_fleisher_gaskin_hitchcock_poncet_schomberg_et al._2022, title={Cover crop residue decomposition in no-till cropping systems: Insights from multi-state on-farm litter bag studies}, volume={326}, ISSN={["1873-2305"]}, DOI={10.1016/j.agee.2021.107823}, abstractNote={Cover crop (CC) residue decomposition influences the provisioning of agroecosystem services. While several laboratory and field studies have investigated processes and mechanisms of CC residue decomposition at specific point or plot scales, regional assessment of factors controlling decomposition rates (i.e., k-values) in no-till corn (Zea mays L.) systems are currently lacking. Here, we conducted the first multi-state on-farm litter bag studies over 105 site-years in the mid-Atlantic and Southeastern US states to determine the independent and combined effect of factors intrinsic to the field (soil and weather) and extrinsic or management factors (CC quantity and quality) on k-values. In the coastal plain regions, the k-values decreased as the underlying soils became sandier. Among weather variables, mean daily air relative humidity (RH) and number of rainy days showed stronger control on k-values than cumulative rainfall. This suggests faster decomposition of CC residues in humid environments and in site-years with frequent rain-events. Among extrinsic factors, the k-values decreased with higher CC biomass, C:N, residue holo-cellulose concentrations, and lignin:N, but increased with higher residue carbohydrate concentrations. The combination of CC residue quality (C:N and holo-cellulose) and weather (RH and rainy days) variables accounted in total for 69% of the variability in k-values with CC residue quality having a greater control over k-values than does weather in the mid-Atlantic and Southeastern US states. Therefore, our study emphasizes the necessity to update current process-based decomposition models to explicitly consider both CC residue quality (C:N, holo-cellulose) and weather factors (RH, rainy days), when predicting CC residue decomposition in no-till cropping systems.}, journal={AGRICULTURE ECOSYSTEMS & ENVIRONMENT}, author={Thapa, Resham and Tully, Katherine L. and Reberg-Horton, Chris and Cabrera, Miguel and Davis, Brian W. and Fleisher, David and Gaskin, Julia and Hitchcock, Richard and Poncet, Aurelie and Schomberg, Harry H. and et al.}, year={2022}, month={Mar} }