Progress 07/01/08 to 09/30/13
Outputs
Target Audience: In 2009-2013 Dr. Grossman mentored 3-4 minority male youth in her laboratory from the School of Science and Math (NCSSM) in Durham, NC, where students carried out short-term research projects related to legume cover crops and rhizobia ecology. Dr. Grossman also served as a guest lecture at NCSSM in 2011, 2012 and 2013 for the Labs for Learning program, designed to pipeline high-potential minority middle school students to NCSSM. All activities involved presentation of research results from this project. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? We mentored 1 post-doc, 5 graduate students, and one 4 undergraduate researchers. How have the results been disseminated to communities of interest? Invited presentations made during campus visits or farmer conferences with content based on work conducted as part of my Hatch project: Grossman, J. Soil fertility in organic systems. Carolina Farm Stewardship Association Conference, November 17, 2012, Durham, NC. Grossman, J. and Hitt, A. Workshop: Cover Crops. To be presented August 19, 2013. Chatham County Cooperative Extension in conjunction with Debbie Roos, Silk Hope, NC. Grossman, J. Putting Legumes to Work on Organic Farms. Annual Sustainable Agriculture Seminar Series, The Pennsylvania State University, January 17, 2013, State College, PA. Grossman, J. Managing Plant-Soil-Microbe Relationships for Better Soil Fertility. Southern Sustainable Agriculture Working Group (SAWG), January 25 and January 26, 2013, Little Rock, AK. Grossman, J. Legume Cover Crops in an Organic System. Carolina Farm Stewardship Association Conference, December, 2012, Greenville, SC. Grossman, J. Diversity of Rhizobia Nitrogen-Fixing Bacteria in Organic Cropping Systems. NCSU Department of Crop Science seminar series, NCSU, March 1, 2012 Grossman, J. Harnessing the Power of Soil Microbes to Enhance Sustainable Agriculture Systems. UNC Pembroke Biology Seminar Series, April 10, 2012, Pembroke, NC Grossman, J. Organic Grains. Organic Commodities and Livestock Conference, January 12 and 13, 2012, New Bern, NC. Grossman, J. Increasing Soil Fertility and Health through Cover Crops. Carolina Farm Stewardship Association Conference, December, 2011, Durham, NC. Reberg-Horton, S.C., Grossman, J. Crozier, C, Hoyt, G. Nutrient management in organic systems, NRCS Webinar, November 30, 2011; 181 electronic participants. Grossman, J. Assessing Nitrogen Contribution and Rhizobia Diversity Associated with Winter Legume Cover Crops in Organic Systems Webinar. eOrganic community of practice. December 14, 2010. Grossman, J. Best Teaching Practices (panelist). Division of Resident Education (A-01), Agronomy/Soil Science Society of America Annual Meeting, Oct 31-Nov 3, Long Beach, CA, 2010. Grossman, J. Soils 101. Carolina Farm Stewardship Association Conference, December, 2010, Black Mountain, NC. Grossman, J. Growing Your Own Soil Fertility with Cover Crops. Organic Growers School, March 6-7, 2010. Grossman, J. Soils 101. Carolina Farm Stewardship Association Conference, December, 2009 Grossman, J. Soil fertility in no-till organic systems. Organic Grains Workshop, Rocky Mount, N.C. 2/28/09 Grossman, J. Soil fertility in organic systems. No-Till Organic Grains Production Workshop, Hoffner Organic Dairy Farm, Cleveland, NC 5/7/09 Grossman, J. Legume cover crops in organic systems at the Center for Environmental Farming Systems. Natural Resource Conservation Service (NRCS) East National Technology Support Center Organics team, Goldsboro, N.C., 5/14/09 Grossman, J. Soil fertility in organic systems. No-Till Organic Grain Production Workshop, Looking Back Farm, Tyner, N.C., 5/28/09 Grossman, J. Outdoor hog production systems, CEFS Board meeting, Goldsboro, N.C. 6/15/09 Grossman, J. The Magic of Mulch: Improving Nutrient Cycling in Organic Farming Systems through Cover Crop Innovations. Biology Department Appalachian State University, Oct 8, 2009, Boone, NC. Grossman, J., Soil fertility management on organic farms. Center for Environmental Farming Systems (CEFS) Brown Bag Seminar Series, June 18, 2009, Raleigh, NC. Grossman, J. Improving soil fertility in organic agriculture: Meeting farmer needs through research. Warren Wilson College Sustainable Agriculture Program, Asheville, N.C., March 23, 2009, Swannanoa, NC. Public Invited Presentations to the Public Edgell, J., Osmond, D. Line, D., Hoyt, G., Grossman, J. Effects of Organic and Conventional Production Systems under Conservation and Conventional Tillage on Water Quality. Tomato Field Day, Mills River, NC, 8/8/2013. Grossman, J. Cover Crops. Breeze Farm Incubator Program, Orange County Cooperative Extension, Hillsborough, NC, 1/8/2012. Grossman, J. Tips: How to Interview. Building Future Faculty program for Minority advanced graduate students and post-doc’s from other institutions interested in faculty careers (organized by Marcia Gumpertz). 3/23/2012 Grossman, J. Invited facilitator, Center for Environmental Farming Systems (CEFS) Movie and Discussion ‘Dirt!’ the movie, in collaboration with the Park Scholarship Program, 3/28/2012. Grossman, J. 49th Soil Microbiology. Annual Resource Conservation Workshop in collaboration with Soil and Water Conservation Districts, 6/25/2012. Larsen, E., Grossman, J., Greg Hoyt, G., Osmond, D., Enhancing soil organic matter in alternative cropping systems: An update. Tomato Field Day, Mills River, NC, August 16, 2012. Grossman, J. and Seehaver, S. Legume cover crops and no-till production. Workshop organizer and leader, ½ day Center for Environmental Farming Systems Seasons of Sustainable Agriculture Workshop Series. 7/12/2012. Grossman, J. Organic no-till corn production. Center for Environmental Farming Systems (CEFS) Field Day, 5/3/2012. Grossman, J. Nutrient management in organic systems. South Carolina NRCS Employee Organic and Sustainable Agriculture Training. USDA Vegetable Laboratory, Charleston, SC 9/25/2012-9/26/2012. Grossman, J. Cover Crop Legumes in No-till Organic Corn Production, Pocosin Organic Farm, Pantego, N.C. Larsen, E., Grossman, J., Greg Hoyt, G., Osmond, D., Enhancing Soil Organic Matter in Alternative Production Systems, Tomato Field Day, Mills River, NC, 8/4/2011. Knowledge and technology transfer to K-12 audiences nvited speaker, Carolina Friends School Geography class.1/17/2012 Invited speaker, North Carolina School of Science and Mathematics ‘Labs for Learning’ program for high-potential minority 9th graders. Annual guest lecture 7/2013, 7/2012, 7/2011, 7/201 Invited speaker, North Carolina School of Science and Math Mini-Term course on local food and sustainable agriculture. 2/24/2012 Invited speaker, NC-Mathematics and Science Education Network (MSEN) Pre-College Program for Bertie county minority high school and middle school students 6/19/201 Invited speaker, Panel Discussion with CEFS faculty and staff for the 1-week Horticultural Science Summer Institute for high school students. 7/10/2012. Press Guest expert PBS Nature series show, “Growing a Greener World” http://www.growingagreenerworld.com/ Aired on National PBS channels during the month of December, 2011. Raleigh News and Observer, Monday, February 7, 2011. “NCSU researchers work to improve soil” Article on Grossman lab research. NCSU University Press Release, January 19, 2011. “Research tests winter cover crops, soil health, on organic farms.” What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Objective 1: We sought to determine effectiveness of commercial inoculants in occupying nodules and in BNF. Commercial rhizobia inoculant is often added at planting to increase legume biological nitrogen fixation (BNF). The winter annual legume cover crops Trifolium incarnatum L. (crimson clover), Vicia villosa Roth (hairy vetch and woolypod vetch), and Pisum sativum subsp. Arvense L. (Austrian winter pea) were planted in a randomized split plot design with and without commercial seed inoculation on three organically managed farms. Legume biomass, biomass nitrogen, nodule number, and nodule dry weight were measured in spring 2011, and Most Probable Number (MPN) assays carried out to determine rhizobia population sizes in sampled field soils. A total of 576 rhizobia strains isolated from surface sterilized nodules of subsampled plants from all treatments were fingerprinted using rep-PCR and sequencing of nodulation gene nodC to determine origin and diversity of nodule rhizobia strains. At three field sites, legume inoculation did not result in an increase in plant biomass, biomass nitrogen, nodule number, or mass. A majority of rhizobia isolates belong to 13 DNA fingerprint clusters whose occupants were over 70% similar, typically not grouping by cover crop host, farm location, or inoculation treatment. As few as 8.5% of strains isolated from inoculated nodules had DNA fingerprints closely related to the commercial inoculant. Fingerprinted strains similar to inoculants had genetically distinct nodC sequences from inoculants, suggesting that applied inoculant strains are not present in host nodules. Objective 2: Many organic farmers incorporate legume cover crops into the soil before planting, but increased interest in reducing tillage has promoted research into alternative cover crop management systems and implements. The roller-crimper is a tractor-mounted implement with a water-filled rolling drum that terminates a cover crop by crimping the stems while leaving the root system and soil undisturbed. For optimum yield, corn in North Carolina is usually planted before early April to avoid overlap of drought-sensitive growth stages with a historical dry period in the end of June. This early planting date falls before most winter annual cover crops’ point of peak biomass and N accumulation and, because cover crops are often incorporated 2 to 3 wk before planting, could result in a significant loss of potential N delivery to the system. The southern-adapted hairy vetch cultivars AU Merit and AU Early Cover reach 50% flowering 15 d earlier than other hairy vetch cultivars or common vetch, and crimson clover cultivars AU Sunrise and AU Robin flower earlier than the traditionally used cultivars Tibbee or Dixie. We hypothesized that high total Ndfa (N derived from the atmosphere) and total N in cover crops that are sensitive to termination by the roller-crimper will be associated with high grain yields in a succeeding corn crop. We tested this hypothesis by (i) measuring the biomass production and total N accumulation at three potential kill dates, (ii) determining the percentage of Ndfa at the optimal kill date, and (iii) identifying roller-crimper-compatible legume species for North Carolina organic corn production systems. The study was conducted at two sites in 2009. For details see the article in Agronomy Journal. Treatments included hairy vetch (Vicia villosa), common vetch (Vicia sativa), crimson clover (Trifolium incarnatum), Austrian winter pea (Pisum sativum), berseem clover (Trifolium alexandrinum), subterranean clover (Trifolium subterraneum), narrow leaf lupin (Lupinus angustifolius), and balansa clover (Trifolium michelianum), as well as bicultures of rye (Secale cereale), hairy vetch, and Austrian winter pea. Hairy vetch and crimson clover had greatest overall biomass of monocultures, while bicultures had greatest biomass in 2010. All cover crops except lupin and subterranean clover derived between 70 and 100% of their N from the atmosphere. Highest corn yields were achieved in hairy vetch and rye+hairy vetch bicultures. Crimson clovers were easiest to terminate via roller in late April, hairy vetches and Austrian winter peas were susceptible to termination in mid May, berseem clover and common vetch in late May. Objective 3: Based on the results of this work we set out to determine the effect of termination approach, including roller-crimper termination, on N release under cover crop mulches. Four different methods of termination including tillage and no-till approaches were used with four winter annual leguminous cover crops to investigate the rate of plant available nitrogen (N) mineralized from decomposing biomass. Corn (Zea mays L.) was planted into an organic cropping system following termination treatments to determine if N availability impacted yield. Termination was accomplished by roller-crimper, flail mower, disk, and herbicide. Cover crop treatments included Austrian winter pea (Pisum sativum subs. arvense), hairy vetch (Vicia villosa var. ‘AU Early Cover’), balansa clover (Trifolium balansae) and crimson clover (Trifolium incarnatum var. ‘Dixie’). Soil N was most available from Austrian winter pea and hairy vetch across termination methods at six to ten weeks after kill. Disked hairy vetch contributed the greatest soil N among all 16 combinations. Biomass ranged from 2.4 Mg ha-1 in balansa clover to 9.7 Mg ha-1 in crimson clover. The three year average biomass production was greater than 7 Mg ha-1, not including balansa. Overall, hairy vetch produced the greatest average biomass nitrogen of 226.4 kg ha-1, while Austrian winter pea averaged 188.71 kg ha-1 and crimson clover averaged 181.1 kg ha-1. In a separate evaluation we assessed winter annual legume root decomposition to determine their contribution to soil organic matter. Winter annual legume cover crop roots decompose slowly relative to shoots and can be an important source of long-term soil organic carbon (SOC) in agro-ecosystems. In this investigation, we characterized three species for root morphological characteristics relevant to decomposition and conducted an incubation to determine the effects that root morphology and soil inorganic N content have onroot decomposition. Austrian winter pea (Pisum sativum), crimson clover (Trifolium incarnatum), and hairy vetch (Vicia villosa Roth) were characterized for total root length, percent fine roots (< 1-mm diameter), and total surface area in a greenhouse study. For all species, fine roots dominated (> 70% of total roots) and also had greater surface area than coarse roots. This morphological analysis was followed an incubation in which crimson clover and hairy vetch coarse (> 1-mm diameter) and fine root decomposition under natural and elevated soil N (~ 200 kg/ha) was measured in terms of mass loss over 12-weeks. Soil inorganic N content did not affect root decomposition, but root litter chemistry as well as root surface area likely played a greater role. Fine roots decomposed faster than coarse roots for both species, and decomposition rates between species within root size fractions were similar. After 12 weeks, crimson clover and hairy vetch roots from coarse and fine root fractions released 66-77% and 77-82% of N, respectively. Having a better understanding of legume cover crop coarse and fine root decomposition dynamics can provide greater insight into their role in SOC buildup and nutrient cycling.
Publications
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2013
Citation:
Grossman, J., Seehaver, S., Sooksa-nguan, T., Parr, M. Effects of Vicia Villosa cover crop inoculation on rhizobia ecology in organic farming systems of the Southeastern United States. Soil Science Society of America Annual Meeting Nov 3-6, 2013, Tampa, FL.
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2013
Citation:
Jani, A. Grossman, J., Hu. S. and Smyth, T.J. Effect of Root Morphology and Termination Approach on Legume Cover Crop Root Decomposition, 98th ESA Annual Meeting August 4 - 9, 2013, Minneapolis, MN.
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2013
Citation:
Bloszies, S.A., J.M. Grossman, J.L. Heitman, S.C. Reberg-Horton, S. Hu. Managing for soil carbon in organic agroecosystems with cover crops and reduced tillage. Soil Science Society of North Carolina Annual Meeting, January 22, 2013.
- Type:
Journal Articles
Status:
Accepted
Year Published:
2013
Citation:
Parr, M., Grossman, J.M., Reberg-Horton, C.; Crozier, C, Brinton, C. 2013 Nitrogen cycling under roller-crimper-terminated legume cover crops in North Carolina organic corn production, In Press; Communications in Soil Science and Plant Analysis, In Press.
- Type:
Journal Articles
Status:
Accepted
Year Published:
2013
Citation:
Mothapo N.V., Grossman, J.M., Maul, J. Shi, W., Brauer, S. 2013. Cropping history affects nodulation and symbiotic efficiency of distinct hairy vetch genotypes with resident soil rhizobia. Biology and Fertility of Soils.
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Progress 10/01/11 to 09/30/12
Outputs
OUTPUTS: Organic corn production is challenged by nitrogen (N) limitations and weed pressures and growers in North Carolina are seeking improved methods to deliver N to grain crops using no-till strategies. The common practice of incorporating legume cover crops for N supply to a succeeding corn crop often leads to N release with a lack of corn crop synchrony. Organic growers also have a need to understand the nitrogen-fixing rhizobia bacteria associated with legume cover crops commonly used in NC, and how agricultural management and environmental conditions interact to influence the rate of nitrogen fixation in cover crop legumes. In 2011-2012, two fields, located in Kinston and Goldsboro/ Center for Environmental Farming Systems (CEFS), NC were established including three over crop species (hairy vetch, crimson clover, and Austrian winter pea) and four termination treatments (flail, disk, roll, and chemical-spray). Decomposition parameters included activities of three lignin-cellulose extracellular enzymes, net C and N mineralization of shoots and roots, nitrification potential, and soil aggregation. Work evaluating management effects on rhizobia diversity continued, with 350 rhizobia strains compatible with the hairy vetch (Vicia villosa) cover crop legume species screened for expression of the nitrogen-fixation nitrogenase gene (NifH). Strains screening positive for the NifH gene were fingerprinted using rep-PCR and 25 strains were selected for further study. A growth chamber study has been initiated to determine selected strain effects on nodule mass, plant biomass, and total plant nitrogen, and these strains are being sequenced to determine genomic difference among strains compatible with hairy vetch. A new international study was initiated in the country of Malawi (Southeast Africa) to determine rhizobia diversity beneath promiscuous varieties of soybean being evaluated to increase both food security and soil fertility. We mentored 1 post-doc, 5 graduate students, and one undergraduate. Events included one workshop Seasons of Sustainable Agriculture workshop series at CEFS emphasizing proper inoculation of cover crop legume seeds to positively affect growth and development of cover crop legumes. Six additional 1.5h workshops were conducted in Malawi in March 2012 sharing information on legume nitrogen fixation and soil health. PARTICIPANTS: Julie Grossman, PI, Supervises laboratory, post-doctoral researcher, and undergraduate trainees, Shuijin Hu, Department of Plant Pathology NCSU co-advises soil aggregation assessment; Wei Shi, Department of Soil Science NCSU co-advises enzyme assessment; G.B. Reddy, NC Agricultural and Technical University, oversees all shoot decomposition and quantification work; Sieglinde Snapp, Department of Crop and Soil Science at Michigan State University is a collaborator on the Malawi rhizobia diversity work, Jude Maul, Ecologist with USDA-ARS Sustainable Agriculture lab assists with rhizobia diversity analysis; . Amanda Roth is a biology undergraduate student assisting with the rhizobia diversity experiments and learning lab culture techniques. Another undergraduate researcher, Jacob Rutz, secured an undergraduate research award and conducted root carbon field assessments. Suzanne Fleishman is an undergraduate at UNC-Chapel Hill conducted research in our lab analyzing data concerning inoculant use practices of organic farmers in the Southeast. TARGET AUDIENCES: Minority and under-served target audiences: In 2011 and 2012 Dr. Grossman mentored 3 minority male youth in her laboratory from the School of Science and Math (NCSSM) in Durham, NC, where students carried out short-term research projects related to legume cover crops and rhizobia ecology. Dr. Grossman also served as a guest lecture at NCSSM in 2011 and 2012 for the Labs for Learning program, designed to pipeline high-potential minority middle school students to NCSSM. All activities involved presentation of results from research funded by this project. All workshops carried out in Malawi were targeting rural subsistence farmers who are learning to use legumes to increase human health and soil fertility. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
In 2011 enzyme activities showed no difference between cover crop treatments and controls with no cover crop. In 2012, all cover crop treatments appeared to increase enzyme activities except for peroxidase, when compared with control treatments. Among cover crop species, hairy vetch showed the least effect on enzyme activity. For termination methods, chemical desiccation had the lowest enzyme activity in both years. Flail mowing stimulated enzyme activity more than disking or spraying in 2011. However, the difference between flail and disk treatments disappeared in 2012. With regard to soil aggregation at Kinston, prior to termination, there were no differences in either mean-weight-diameter (MWD) within individual size fractions between all species and the control plots. Fourteen weeks post-termination, there was again no difference in either MWD or individual size fractions between ground covers or between termination approaches. Microbial biomass carbon was considerably higher at CEFS in 2012 than in Kinston. At this site, before termination, significant depth and cover-depth interaction effects were found. After termination, significant cover crop species, depth, cover-termination method-depth interaction, date and cover-date interaction effects were found. When monitoring root decomposition at Kinston, a trend of more rapid decomposition of crimson clover compared to the other cover crops over the 16-week period. Crimson clover roots had the lowest lignin content and highest surface area, both of which are conducive to rapid decomposition. However, no significant differences in decomposition between species at CEFS were observed. Termination method effect on decomposition was significant for some treatments in both locations. The main effect of termination method was significant in Kinston with roots from all rolled plots decomposing faster than in disked plots. At this same site, the general trend was for slower initial rate of decomposition within 4 weeks of termination in bare plots where cover crops were not grown. At CEFS, there was no overall effect of termination approach on decomposition rate, however the trend of slower decomposition rate in control plots was observed over the entire 16-week period. Morphologically, crimson clover was found to produce significantly greater total root length than both Austrian winter pea and hairy vetch. Hairy vetch, in turn produced greater total root length than Austrian winter pea. Crimson clover also produced greater total fine root length (< 2.0 mm) than Austrian winter pea and hairy vetch. From our work in Malawi, over 500 rhizobia strains have been isolated from soybean nodules, soils from 40 study sites assessed for nutrient status, and are undergoing further genetic analysis in our NC lab. Workshops conducted in Malawi were estimated to reach over 150 individuals in total, all from low-income subsistence farming operations, and many women.
Publications
- Grossman, J. 2012 Legume inoculation for organic farming systems, peer-reviewed eOrganic / eXtension publication, http://www.extension.org/pages/64401/legume-inoculation-for-organic-f arming-systems
- Fleishman, S., Grossman, J., Larsen, E. and Bowen, S. 2012 Grower Adherence to Legume Cover Crop Rhizobia Inoculant Maintenance and Use Recommendations in the Southeast. Soil Science Society of America Annual Meeting. October 22-24th 2012, Cincinnati, OH.
- Brown, M., Grossman, J. Horton, S.C. and Shi, W. 2012 The Influence of Termination Techniques On Plant Available Nitrogen Mineralized From Winter Annual Leguminous Cover Crops. Soil Science Society of America Annual Meeting. October 22-24th 2012, Cincinnati, OH.
- Brown, M., Shi, W., Reberg-Horton, S.C. 2012 Evaluating termination methods of leguminous cover crops for optimizing nitrogen synchrony, Ecological Society of America Conference, 97th Annual, August 5th-10th, Portland, OR.
- Liang ST, Grossman J, Shi W. 2012 Microbial response to winter cover cropping management during transition to organic farming. ASA, CSSA, and SSSA international annual meetings; 2012 Oct 21-24; Cincinnati, OH.
- Rutz, J., Grossman, J. Jani, A. 2012 Potential contributions of legume cover crop root biomass to labile organic matter pools. ASA, CSSA, and SSSA international annual meetings; 2012 Oct 21-24; Cincinnati, OH.
- Parr, M. and Grossman, J. 2012 Drivers of Soybean Rhizobia Diversity in Uninoculated Soils of Smallholder Farms in Malawi. Soil Science Society of America Annual Meeting. October 22-24th 2012, Cincinnati, OH.
- Bloszies, S., S. Hu, C. Reberg-Horton, J. Grossman, and J. Heitman 2012 Managing for soil carbon in organic agroecosystems with cover crops and reduced tillage. CEFS Field Day, May 2, 2012, Goldsboro, NC.
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Progress 10/01/10 to 09/30/11
Outputs
OUTPUTS: Both certified organic crops and those grown in regions where fertilizer is less accessible are often challenged by nitrogen (N) limitations. In parallel, conventional growers are concerned about the rising costs of N fertilizer, making alternative approaches to N management all the more appealing. To overcome these challenges, growers are seeking improved methods to deliver N to their farming systems. For these reasons, there is renewed interest in the practice of incorporating legume cover crops into crop rotations. Biological nitrogen fixation (BNF) through the legume-rhizobia symbiosis is a major contributor of nitrogen to farming systems around the globe, with presence of effective rhizobia strains being essential for optimal nodulation of legume cover crops and green manures. Farmers would like enhanced understand of the effectiveness and efficiency of the legume-rhizobia symbiosis and how agricultural management and environmental conditions interact to influence the rate of nitrogen fixation in cover crop legumes. Experiments conducted as part of this project and their associated results are described under 'outputs'. Events in 2011 included two field days (Legume Nitrogen Fixation held on a farmer field, and the Mountain Horticultural Research Station field day), three regional grower workshops (Organic Growers School (2) and Carolina Farm Stewardship Association), two outreach events to youth (NC School of Science and Math; Carolina Friends School), and formal research presentations 5 national/international, and 3 regional. Mentoring as part of this project included six graduate students under my advisement. I am on the committees of seven additional graduate students. PARTICIPANTS: Individuals: None besides Julie Grossman were paid salary using project funds. Partner organizations: NC School of Science and Mathematics, Durham, NC; USDA Sustainable Agriculture Laboratory, Beltsville M.D.; Inter-Faith Food Shuttle, Raleigh, NC; Longview Public Alternative School, Raleigh, NC. Collaborators and contacts: Deanna Osmond, Department of Soil Science; Greg Hoyt, Department of Soil Science/Horticulture; Wei Shi, Department of Soil Science; Owen Duckworth, Department of Soil Science; NCSU Collaborators. Shuijin Hu, Department of Plant Pathology; Chris Reberg-Horton, Department of Crop Science; Michelle Schroeder-Moreno, Department of Crop Science; Jude Maul, USDA Sustainable Agriculture Laboratory, Beltsville M.D.; Sieglinda Snapp, Department of Crop Science, Michigan State University. Training or Professional Development: I directly advise six graduate students, and three undergraduate or high school level researchers. The first, Nape Mothapo, successfully defended her M.S. with a thesis investigating nodulation and rhizobia diversity associated with genetically distinct hairy vetch populations. My PhD student Mary Parr was awarded an NSF Graduate Research Fellowship and is currently conducting her research in Malawi investigating biological diversity of soybean-nodulating rhizobia. Matthew Brown is a M.S. student investigating how legume cover crop termination method affects N mineralization rate. Arun Jani is a M.S. student studying the contribution of cover crop roots to soil C and N pools. Erika Larsen is a M.S. student investigating the role of organic soil management in reducing soil runoff. Finally, Sarah Seehaver is addressing the need for inoculation on three organic farms across the state. Additionally, I served on the advisory committees of seven additional students. Two undergraduate research scholars were mentored (Brenna Hannapel and Dan Kiser), as well as one minority high school student from the NC School of Science and Math (Malik Oliver). TARGET AUDIENCES: Target Audiences: This research conducted for this project primarily serves organic growers in the United States, however we are now expanding our research to include legume use for soil fertility improvement in marginalized low-income communities in Africa (Malawi). Efforts: Julie Grosssman (PI) teaches three courses at NC State: Biological Approaches to Sustainable Soil Management (SSC 427), Service-Learning for Sustainable Soil Management in Community Gardens (SSC 428), and the graduate level Issues in Sustainable Agriculture Systems (SSC 495). Dr. Grossman's teaching program is closely connected to the Inter-Faith Food Shuttle (IFFS) and their community gardening initiative in low-income Raleigh neighborhoods. IFFS's mission is to alleviate hunger by developing systems to recover, prepare and distribute wholesome, perishable food for the area's poor, hungry, undernourished and homeless. In Dr. Grossman's service-learning course (SSC 428) teams of NCSU students develop agricultural curriculua for youth and deliver their lessons over an 8-week period at IFFS's community garden sites. Many NCSU students are interested in eventually working with organizations that emphasize youth development through sustainable agriculture, especially as it relates to under-represented groups. To help prepare students to be successful food system leaders, Dr. Grossman is actively conducting research to better understand student learning resulting from courses that emphasize service-learning in a community garden setting. In particular, she is interested in understanding how these courses help students gain cultural competency, leadership, problems solving, and community outreach skills. We are also actively involved in minority training for minority students at the NC School of Science and Math (NCSSM) in Durham. As part of that collaboration, Dr. Grossman conducts 2-3 lectures each year for minority students and hosts 2-4 NCSSM minority males in her lab each summer as part of a mentored research experience. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
An experiment was designed and carried out in 2011 to test a hypothesis that rate of legume cover crop N mineralization is impacted by termination approach. Four winter annual cover crop varieties were grown in North Carolina to determine biomass nitrogen (N) production and N release rate when killed via rolling-crimping, mowing, incorporation and herbicide. Cover crops included hairy vetch (Vicia villosa), crimson clover (Trifolium incarnatum), Austrian winter pea (Pisum sativum) cv. Whistler, and balansa clover (Trifolium michelianum) cv. Frontier. Total biomass, N concentration, C:N ratios, and N flux over 12 weeks were determined. Crimson clover had the greatest overall biomass, however hairy vetch contained the greatest N content. Greatest N flux appeared to occur at 6-weeks following termination under the rolled-crimped treatment. This experiment will continue in 2012. Our rhizobia ecology research in 2011 evaluted nodulation effectiveness and diversity of rhizobia found in low-input and organic systems. Specifically, we continued our evaluation of soils with and without history of hairy vetch cultivation with distinct hairy vetch (HV) genotypes. Fields which had previously grown HV showed appreciable nodulation, with an average of 49% more nodules and 51% more nodule mass compared to fields without history. Like nodulation, nitrogen-fixation was more efficient in fields with HV history, with plants containing nearly 50% more biomass N than plants from fields with no vetch history. Plant biomass and plant tissue nitrogen were linearly correlated to nodule mass (r2 = 0.80 and 0.56 respectively). Molecular approaches (rep-PCR) demonstrated large diversity in resident rhizobia populations within and between fields overall. Cluster analysis of 480 isolates resulted in 36 genetic groups of rhizobia. We also began an international study evaluating rhizobia diversity and nitrogen fixation for smallholder farmers in Malawi (Southeast Africa). We will test the hypotheses that rhizobia communities vary in both species and ecotype composition with soil properties, as well as field history, and that field history will have a strong influence on the diversity of rhizobia ecotypes.
Publications
- Reberg-Horton, C, Grossman, J., Kornecki, T.S., Meijer, A.D., Price, A.J., Place, G., Webster, T.M. 2011. Utilizing cover crop mulches to reduce tillage in organic systems in the Southeastern USA. Renewable Agriculture and Food Systems, In Press; available online: doi:10.1017/S1742170511000469.
- Parr, M.; Grossman, J.M.; Reberg-Horton, S.C.; Brinton, C. and Crozier, C. 2011. Nitrogen fixation of legume cover crops in no-till organic corn production, Agronomy Journal 103(6), 1578-1590.
- Grossman, J.M.; Schipanski, M.E.; Sooksanguan, T.; Drinkwater, L.E. 2011. Diversity of rhizobia nodulating soybean [Glycine max (Vinton)] varies under organic and conventional management, Applied Soil Ecology, 50, p. 14-20.
- Parr, M., Grossman, J., Snapp, S. Sustainable nutrient management and agrobiodiversity in Africa. Ecological Society of America Annual Meeting August 7-12, 2011, Austin, TX
- Mothapo, N. Maul, J., Grossman, J. Hairy vetch use affects nodulation and diversity of Rhizobium leguminosarum. Graduate student research symposium, NC State, April, 2011 (1st Place, Graduate Student Poster Competition)
- Oliver, M., Grossman, J., Mothapo, N. Improving organic agriculture by quantifying legume cover crop rhizobia soil populations, 20th Annual NC State Undergraduate Research Spring Symposium, April 12, 2011, Raleigh, NC.
- Parr, M. and Grossman, J. Nitrogen Fixation and Legume Cover Crops in North Carolina. Fifty-Fourth Annual Meeting of the Soil Science Society of North Carolina, January 19-20, 2011, Raleigh, NC.
- Reberg-Horton, S. C., Wells, S, Smith, A., Grossman, J., Parr, M. and Place, G., Weed Management Impacts of Roll Killed Cover Crops for Organic Corn and Soybeans, S. Northeast Weed Society Meeting, Jan 3-6, 2011, Baltimore, MD.
- Grossman, J. , Sooksanguan, J., Parr, M., Seehaver, S. Diversity of Hairy Vetch (Vicia villosa) Cover Crop Rhizobia Symbionts Varies Among Field Inoculated Plants and Naturalized Populations. Soil Science Society of American Annual Meetings, Long Beach, CA. Nov 1-5, 2010.
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