@article{o'connell_grossman_hoyt_shi_bowen_marticorena_fager_creamer_2015, title={A survey of cover crop practices and perceptions of sustainable farmers in North Carolina and the surrounding region}, volume={30}, DOI={10.1017/s1742170514000398}, abstractNote={Abstract}, number={6}, journal={Renewable Agriculture and Food Systems}, author={O'Connell, S. and Grossman, J. M. and Hoyt, G. D. and Shi, Wei and Bowen, S. and Marticorena, D. C. and Fager, K. L. and Creamer, N. G.}, year={2015}, pages={550–562} }
 @article{edgell_osmond_line_hoyt_grossman_larsen_2015, title={Comparison of Surface Water Quality and Yields from Organically and Conventionally Produced Sweet Corn Plots with Conservation and Conventional Tillage}, volume={44}, ISSN={["1537-2537"]}, DOI={10.2134/jeq2015.02.0074}, abstractNote={Organic agricultural systems are often assumed to be more sustainable than conventional farming, yet there has been little work comparing surface water quality from organic and conventional production, especially under the same cropping sequence. Our objective was to compare nutrient and sediment losses, as well as sweet corn ( L. var. ) yield, from organic and conventional production with conventional and conservation tillage. The experiment was located in the Appalachian Mountains of North Carolina. Four treatments, replicated four times, had been in place for over 18 yr and consisted of conventional tillage (chisel plow and disk) with conventional production (CT/Conven), conservation no-till with conventional production (NT/Conven), conventional tillage with organic production (CT/Org), and conservation no-till with organic production (NT/Org). Water quality (surface flow volume; nitrogen, phosphorus, and sediment concentrations) and sweet corn yield data were collected in 2011 and 2012. Sediment and sediment-attached nutrient losses were influenced by tillage and cropping system in 2011, due to higher rainfall, and tillage in 2012. Soluble nutrients were affected by the nutrient source and rate, which are a function of the cropping system. Sweet corn marketable yields were greater in conventional systems due to high weed competition and reduced total nitrogen availability in organic treatments. When comparing treatment efficiency (yield kg ha /nutrient loss kg ha ), the NT/Conven treatment had the greatest sweet corn yield per unit of nutrient and sediment loss. Other treatment ratios were similar to each other; thus, it appears the most sustainably productive treatment was NT/Conven.}, number={6}, journal={JOURNAL OF ENVIRONMENTAL QUALITY}, author={Edgell, Joshua and Osmond, D. L. and Line, D. E. and Hoyt, G. D. and Grossman, J. M. and Larsen, E. M.}, year={2015}, pages={1861–1870} }
 @article{bordeaux_grossman_white_osmond_poore_pietrosemoli_2014, title={Effects of rotational infrastructure within pasture-raised pig operations on ground cover, soil nutrient distribution, and bulk density}, volume={69}, ISSN={["1941-3300"]}, DOI={10.2489/jswc.69.2.120}, abstractNote={Interest in pasture-based pork products has increased significantly in recent years. However, nitrogen (N) losses resulting from these systems are common due to importation of feed, high stocking rates, and pig behavior. This study was conducted to evaluate soil inorganic N, soil-test phosphorus (STP), ground cover, and compaction changes as impacted by rotational shade, water, and feed structures in a pasture-raised pig operation over two 12-week pig occupations. Shade and watering structures were rotated weekly for 12 weeks within a rotational (mobile) scheme; data were compared to a stationary structure system as well as to a managed hay operation with no pigs. Soil samples were acquired from subplots and analyzed for distribution of inorganic N concentrations among main plot treatments, including nitrate (NO3), ammonium (NH4), and STP values. Soil inorganic N concentrations were higher in exterior subplot positions than in interior positions. This pattern was not maintained after a second pig group occupied the plots. Soil test phosphorus was unaffected by either pig occupation. Ground cover percentages were higher in control (hay) treatments than for pig treatments, however no difference was found between mobile and stationary structure treatments in either pig occupation. Soil compaction, as measured by soil bulk density, was found to be higher under permanent shade structure locations as compared to mobile and control treatments. Mobile and control compaction levels were not different for the second occupation, utilizing a more intensive sampling scheme, suggesting a benefit to the rotation of shade, water and feed infrastructure. The weekly rotation of infrastructure performed during both occupations was both labor intensive and time consuming. The observed lack of improvement in nutrient distribution to a rotational infrastructure may limit its utility in pastured-pig systems. However, further options are available that would allow the production of pasture-raised pigs while minimizing associated nutrient loading and pasture degradation.}, number={2}, journal={JOURNAL OF SOIL AND WATER CONSERVATION}, publisher={Soil and Water Conservation Society}, author={Bordeaux, C. and Grossman, J. and White, J. and Osmond, D. and Poore, M. and Pietrosemoli, S.}, year={2014}, pages={120–130} }
 @article{parr_grossman_reberg-horton_brinton_crozier_2014, title={Roller-Crimper Termination for Legume Cover Crops in North Carolina: Impacts on Nutrient Availability to a Succeeding Corn Crop}, volume={45}, ISSN={["1532-2416"]}, DOI={10.1080/00103624.2013.867061}, abstractNote={Nitrogen (N) release from roll-killed legume cover crops was determined for hairy vetch (Vicia villosa Roth), crimson clover (Trifolium incarnatum L.), and a hairy vetch + rye (Secale cereale L.) biculture in an organic corn production system in North Carolina, USA. Cover crops were planted at two locations in fall 2008 and 2009, roll-killed in May, and no-till planted with corn (Zea mays L.). Inorganic soil N and mineral N flux were determined using potassium chloride (KCl) extractions and ion-exchange resin (Plant Root Simulator, PRS) probes at 2-week intervals for 12 weeks and compared to fertilized controls of 0 and 168 kg N ha−1. In 2009, greater plant available N under hairy vetch than under either 0 N control or crimson clover was found, with peak soil N occurring between 4 and 6 weeks after roll kill. Available soil N under crimson clover mulches was less than or equal to 0 N, suggesting net immobilization.}, number={8}, journal={COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS}, publisher={Informa UK Limited}, author={Parr, Mary and Grossman, Julie M. and Reberg-Horton, S. Chris and Brinton, Carrie and Crozier, Carl}, year={2014}, month={Apr}, pages={1106–1119} }
 @article{larsen_grossman_edgell_hoyt_osmond_hu_2014, title={Soil biological properties, soil losses and corn yield in long-term organic and conventional farming systems}, volume={139}, ISSN={["1879-3444"]}, DOI={10.1016/j.still.2014.02.002}, abstractNote={Topsoil losses through surface runoff have severe implications for farmers, as well as surrounding ecosystems and waterbodies. However, integrating management systems that enhance soil organic matter (SOM) can stabilize the soil surface from erosion. Little is known about how differences in both tillage and cropping system management affect carbon and subsequent sediment losses in horticultural fields, particularly in the humid climate of the southeast. Research was conducted in the Appalachian Mountains in Mills River, NC on a fine-sandy loam Acrisol from 2010 to 2012 on long-term plots established in 1994. Project objectives included to: (1) quantify labile and total organic matter based on tillage and cropping system practices, (2) determine if relationships exist between SOC ad sediment losses, and (3) determine long-term management and tillage impacts on total organic matter lost via runoff. We hypothesized that organic management and reduced tillage would lead to increased soil carbon, which subsequently reduce losses as soil is stabilized. Organic no tillage and conventional till treatments contained on average 14.34 and 6.80 g kg−1 total carbon (TC) respectively, with the organic no till treatments containing twice the quantity of TC and light fraction particulate organic matter (LPOM) in the upper 15 cm as compared with the conventionally tilled treatments, and four times the quantity of microbial biomass carbon (MBC). LPOM and HPOM, the heavier fraction of POM, did not differ in the organic till and conventional no till treatments.Data support our hypothesis that organic production in combination with no tillage increases C pools (both total and labile) as compared with tilled conventional plots. However, organic no till treatments produced sweet corn (Zea mays var. saccharata) yields less than 50% of that of conventional treatments, attributed to weed competition and lack of available N. No tillage treatments lost two to four times less soil C via surface runoff than tilled systems. Additionally, we found that as total soil C increased, suspended solids lost through surface runoff decreased. Overall, our results indicate tillage to be an important factor in enhancing soil C and decreasing soil loss through surface runoff.}, journal={SOIL & TILLAGE RESEARCH}, author={Larsen, Erika and Grossman, Julie and Edgell, Joshua and Hoyt, Greg and Osmond, Deanna and Hu, Shuijin}, year={2014}, month={Jun}, pages={37–45} }
 @article{liang_grossman_shi_2014, title={Soil microbial responses to winter, legume cover crop management during organic transition}, volume={65}, ISSN={["1778-3615"]}, DOI={10.1016/j.ejsobi.2014.08.007}, abstractNote={Legume cover cropping has been widely used as an efficient strategy to improve soil fertility. Although this management practice is important to resolve N deficiency for the transition from conventional to organic production systems, optimization is necessary to determine legume cover crop species and termination methods. This study used soil microbial properties and processes to evaluate the suitability of several legume cover crops and termination methods for organic transition in southeastern USA. Soil samples were taken from two newly-established study sites, each containing 12 treatments of three termination methods (disk, flail, and spray) and four cover types (no cover crop, Austrian winter pea, hairy vetch, and crimson clover). Compared to disking and spraying, flail mowing significantly increased soil microbial biomass C by ∼17%, C mineralization by ∼25%, N mineralization by ∼16%, and nitrification potential by ∼36%, 12 weeks after cover crop termination. However, cover cropping only stimulated nitrification potential, but not C and N mineralization. Furthermore, the activities of soil enzymes (exoglucanase, β-glucosidase, and β-glucosaminidase) appeared to be more responsive to cover types than to termination methods. Among three cover crops, Austrian winter pea showed the greatest positive effects on nitrification potential, β-glucosidase, and β-glucosaminidase. The ratio of C mineralization to microbial biomass C also differed with cover types, being lowest in Austrian winter pea. Our results indicated that legume species even with small differences in C-to-N ratio and lignin and cellulose contents could have varied effects on soil microbial properties and processes. Nitrification potential, representing the function of a small group of soil microbial community, was proved to be sensitive to both legume species and termination methods.}, journal={EUROPEAN JOURNAL OF SOIL BIOLOGY}, author={Liang, Shangtao and Grossman, Julie and Shi, Wei}, year={2014}, pages={15–22} }
 @article{mothapo_grossman_sooksa-nguan_maul_bräuer_shi_2013, title={Cropping history affects nodulation and symbiotic efficiency of distinct hairy vetch (Vicia villosa Roth.) genotypes with resident soil rhizobia}, volume={49}, ISSN={0178-2762 1432-0789}, url={http://dx.doi.org/10.1007/S00374-013-0781-Y}, DOI={10.1007/s00374-013-0781-y}, abstractNote={Compatible rhizobia strains are essential for nodulation and biological nitrogen fixation (BNF) of hairy vetch (Vicia villosa Roth, HV). We evaluated how past HV cultivation affected nodulation and BNF across host genotypes. Five groups of similar HV genotypes were inoculated with soil dilutions from six paired fields, three with 10-year HV cultivation history (HV+) and three with no history (HV−), and used to determine efficiency of rhizobia nodulation and BNF. Nodulation was equated to nodule number and mass, BNF to plant N and Rhizobium leguminosarum biovar viceae (Rlv) soil cell counts using qPCR to generate an amplicon of targeted Rlv nodD genes. Both HV cultivation history and genotype affected BNF parameters. Plants inoculated with HV+ soil dilutions averaged 60 and 70 % greater nodule number and mass, respectively. Such plants also had greater biomass and tissue N than those inoculated with HV− soil. Plant biomass and tissue N were strongly correlated to nodule mass (r 2 = 0.80 and 0.50, respectively), while correlations to nodule number were low (r 2 = 0.50 and 0.31, respectively). Although hairy vetch rhizobia occur naturally in soils, past cultivation of HV was shown in this study to enhance nodulation gene-carrying Rlv population size and/or efficiency of rhizobia capable of nodulation and N fixation.}, number={7}, journal={Biology and Fertility of Soils}, publisher={Springer Science and Business Media LLC}, author={Mothapo, N. V. and Grossman, J. M. and Sooksa-nguan, T. and Maul, J. and Bräuer, S. L. and Shi, W.}, year={2013}, month={Feb}, pages={871–879} }
 @article{mothapo_grossman_maul_shi_isleib_2013, title={Genetic diversity of resident soil rhizobia isolated from nodules of distinct hairy vetch (Vicia villosa Roth) genotypes}, volume={64}, ISSN={["1873-0272"]}, DOI={10.1016/j.apsoil.2012.12.010}, abstractNote={Hairy vetch (Vicia villosa Roth, HV) is widely grown as a legume cover crop throughout the U.S.A., with biological nitrogen fixation (BNF) through symbiosis with Rhizobium leguminosarum biovar viciae (Rlv) being one of the most sought after benefits of its cultivation. This study determined if HV cultivation history and plant genotype affect genetic diversity of resident Rlv. Soil samples were collected from within farmers’ fields at Graham, Cedar Grove and Ivanhoe sites in North Carolina and pairs of genetically similar hairy vetch genotypes used as trap hosts. A total of 519 Rlv strains were isolated from six paired field soils, three with and three without histories of HV cultivation. A total of 46 strains failed to PCR-amplify the nifH gene; however nodC PCR amplification of these nifH-negative strains resulted in amplification of 22 of the strains. Repetitive element polymerase chain reaction (rep-PCR) with BOX-A1R primer and redundancy analysis showed rhizobial diversity to vary greatly within and between fields, with over 30 BOX banding patterns obtained across the six fields. Cluster analysis of BOX-PCR banding patterns resulted in 36 genetic groups of Rlv at a similarity level of 70%, with 15 of the isolates from fields with HV history not belonging to any of the clusters. Site was found to be the main driver of isolate diversity overall, explaining 57%, of the total variation among rhizobia occupying HV nodules, followed by history of hairy vetch cultivation. Evidence of a HV host genotype influence on the populations of rhizobia that infect hairy vetch was also observed, with plant genotype explaining 12.7% of the variation among all isolates. Our results show that second to site, HV cultivation history was the most important driver of rhizobial nodule community structure and increases the genetic diversity of resident Rlv in soils.}, journal={APPLIED SOIL ECOLOGY}, author={Mothapo, N. V. and Grossman, J. M. and Maul, J. E. and Shi, W. and Isleib, T.}, year={2013}, month={Feb}, pages={201–213} }
 @article{wells_reberg-horton_smith_grossman_2013, title={The Reduction of Plant-Available Nitrogen by Cover Crop Mulches and Subsequent Effects on Soybean Performance and Weed Interference}, volume={105}, ISSN={["1435-0645"]}, DOI={10.2134/agronj2012.0396}, abstractNote={A 3 site‐year study was conducted to investigate the impact of roller‐crimped rye (RC) (Secale cereale L.) mulches on soil N immobilization and subsequent effects on weed suppression and soybean [Glycine max (L.) Merr.] yield. Treatments consisted of: (i) RC, (ii) conventional tillage with neither rye cover crop nor weed control measures (WC), (iii) conventional tillage plus herbicide weed control (CT+HB), and, (iv) roller‐crimped rye plus herbicide (RC+HB). The rye biomass varied between the sites with 4400, 8300, and 7084 kg ha−1 dry matter (DM) for Goldsboro 2009, Kinston 2009, and Kinston 2010, respectively. During the season, the flow of soil inorganic N was monitored via ion‐exchange probes and by direct extractions at two depths (0–10 and 10–25 cm) every 2 wk. Tissue data was collected every 2 wk on soybean and redroot pigweed (Amaranthus retroflexus L.) to determine the C/N ratio. For all sites, peak N immobilization occurred between 4 and 6 weeks after planting (WAP), indicated by a reduction in soil inorganic N. Results from the ion‐exchange probes showed similar trends of the extractable soil inorganic N at all sites. Pigweed C/N ratios revealed a growing divergence between the two systems, with a severe N deficiency in the RC. Even with varying rye biomass production across environments the RC system created an extremely low N environment, suggesting that when a cereal cover crop is paired with a legume cash crop, reduced weed crop interference may result, with little reduction in soybean yield.}, number={2}, journal={AGRONOMY JOURNAL}, publisher={American Society of Agronomy}, author={Wells, M. S. and Reberg-Horton, S. C. and Smith, A. N. and Grossman, J. M.}, year={2013}, pages={539–545} }
 @article{reberg-horton_grossman_kornecki_meijer_price_place_webster_2012, title={Utilizing cover crop mulches to reduce tillage in organic systems in the southeastern USA}, volume={27}, ISSN={["1742-1713"]}, DOI={10.1017/s1742170511000469}, abstractNote={Abstract}, number={1}, journal={RENEWABLE AGRICULTURE AND FOOD SYSTEMS}, publisher={Cambridge University Press (CUP)}, author={Reberg-Horton, S. Chris and Grossman, Julie M. and Kornecki, Ted S. and Meijer, Alan D. and Price, Andrew J. and Place, George T. and Webster, Theodore M.}, year={2012}, month={Mar}, pages={41–48} }
 @article{grossman_schipanski_sooksanguan_seehaver_drinkwater_2011, title={Diversity of rhizobia in soybean [Glycine max (Vinton)] nodules varies under organic and conventional management}, volume={50}, ISSN={["0929-1393"]}, DOI={10.1016/j.apsoil.2011.08.003}, abstractNote={Legume cultivation is an important nitrogen source for organic farmers, yet we understand little about how organic agriculture affects rhizobia diversity in the field. We investigated how the suite of practices common in certified organic management affect diversity of rhizobia occupying soybean nodules in the field. We used molecular analysis to evaluate genetic diversity and taxonomic relationships among rhizobia strains across two organically and two conventionally managed fields. Nodule presence of inoculant isolates added at planting was also assessed. We found that the organically managed soybean fields contained a greater diversity of rhizobia isolates than conventionally managed fields, resulting in over 10 clusters containing isolates of over 70% similarity. Each of the two conventional fields was dominated by genetically similar rhizobia by field, with little crossover. One conventional field showed remarkable isolate similarity, with a majority of the isolates being more than 85% similar, and indicating that many of the field isolates were related to the inoculant. In contrast, isolates from organic fields did not group according to farm field from which they were isolated, but instead formed clusters containing a combination of isolates from organically managed soils from both fields, and did not match the inoculant strain genetic composition. This experiment provided evidence that organic management was a strong driver of the rhizobia genotype present in those fields, and further understanding of rhizobia ecology and function as related to specific organic management practices remains a priority.}, journal={APPLIED SOIL ECOLOGY}, author={Grossman, J. M. and Schipanski, M. E. and Sooksanguan, T. and Seehaver, S. and Drinkwater, L. E.}, year={2011}, month={Oct}, pages={14–20} }