Long-Term, Large-Scale Systems Research Directed Toward Agricultural Sustainability

Long-Term, Large-Scale Systems Research Directed Toward Agricultural Sustainability

Summary

An interdisciplinary, systems- research project compared diverse agriculture/ecosystems: a best management practice (BMP) system; an integrated crop/animal system; an organic production system; a forestry/woodlot system; and a successional ecosystem.
Soil nematode population density maxima for most trophic groups was in July.
Three species of beneficial insect-parasitic nematodes, Steinernema carpocapsa, S. glaseri and Heterorhabditis bacteriophora, and two insect-pathogenic fungi, Beauveria and Metarhizium, were isolated from the site. Cumulative abundance of soil microarthropods was greater in the organic, successional and BMP no-till treatments than in the Woodlot, BMP conventional till and pasture plots. Management practices or vegetation types affect on soil microbial biomass C and N, labile soil C pools, microbial activities and functional diversity, and N mineralization were also examined. Carbon and N availability were significantly different among the five ecosystems. While available N and potentially available N were consistently and significantly lower in grassland, forest and successional systems than in the two agricultural ones over the year, C availability was higher in the grassland and organic soils. High C availability and low N in grasslands significantly affected soil microbes and led to higher microbial biomass C:N ratios and lower N mineralization, suggesting a shift of microbial community composition. In the nested transition to organic study soil quality parameters were unaffected by treatment. Nevertheless, and similar to results from 2001, there was a trend for greater soil respiration (evolved CO2) and more rapid infiltration in the organic compared to conventional systems. Likewise, penetrometer resistance, a measure of soil compaction, tended to be greater in the conventional system. No differences were found between systems for field capacity, hydraulic conductivity, plant available water retention and soil microporosity.

Plots in the Long-term Farming Systems Trial at the Center for Environmental Farming Systems containing three replications and five sampling points within each replication, were sampled in May, July, and September of 2001 and 2002, to determine the effects of various production systems on selected soil abiotic and biotic characteristics.

A minimum data set of soil quality indicators was measure in the systems from 1999-2002. Soil respiration, which was used as an indirect measure of microbial biomass activity produced the most striking results. Carbon evolved in the BMP no-tillage system was approximately eight-fold greater than the conventional tillage system (512 vs. 63 kg C/ha/d) and similar to results for the pasture system (521 kg C/ha/d). Intermediate values, ranging from 240 to 319 kg C/ha/d, were observed for organic, crop/animal, agroforestry, and successional systems. These results suggest a greater level of microbial activity in systems where previous crop/plant residues are maintained on the surface or where animal manures constitute part of the soil fertility regime. Infiltration, measured as the time required for 2.54 cm of water to move into the soil, was notably faster in the organic compared to all other systems and reflects the reliance on cultivation as a weed management tool in organic production.

Soil nematode population density maxima for most trophic groups was at the July sampling. Population densities of nematodes feeding on bacteria and fungi were greater in organic treatments than in conventional cotton culture. Higher densities of these free-living nematodes are probably a result of applications of organic sources of nitrogen including a winter cover crop. Numbers of predatory nematodes were greatest in the woodlot and successional treatments than in other treatments. Population densities of bacterial feeding nematodes were greater in no-till cotton than in conventionally-tilled cotton at all samplings. Numbers of fungal feeding nematodes were greater in no-till than in conventionally tilled cotton at the May and July samplings, but not at the September sampling. Population densities of plant-parasitic nematodes were not affected by tillage regime. The total numbers of plant-parasitic nematodes were greatest in sweet potato culture.

Also examined were how different management practices or vegetation types affect soil microbial biomass C and N, labile soil C pools, microbial activities and functional diversity, and N mineralization. Carbon and N availability were significantly different among the five ecosystems. While available N and potential available N were consistently and significantly lower in grassland, forest and successional systems than in the two agricultural ones over the year, C availability was higher in the grassland and organic soils. High C availability and low N in grasslands significantly affected soil microbes and led to higher microbial biomass C:N ratios and lower N mineralization, suggesting a shift of microbial community composition. Grasses were most effective in reducing soluble N from the soil, tightening N cycling. Although no chemical N fertilizer was applied, organic soils sustained N supply over the growing season. Microbial activities were highest in grassland soils and preliminary data showed that organic and grassland soils had higher functional diversity than conventional agricultural soils. The functional diversity of the microbial community in conventional soils was distinct from that in other ecosystems.

Several nested studies were conducted as part of an ever-growing graduate student program. While one project has been completed, three are ongoing and producing preliminary results. A graduate student in entomology and crop science is evaluating beneficial insect habitats, which are increasingly being employed by growers on small farms in the South. The objectives of this research are to 1) determine what insects (beneficial or otherwise) are attracted to select cut flower crops, cover crops, and commercial beneficial seed blends; 2) examine the purity, germination and on-farm growth characteristics of these commercial seed blends; and 3) to construct and evaluate a simple beneficial insect habitat based on existing literature. One year of field research has been completed. A graduate student in crop science studied the relationship between plant populations in field margins and weed populations in neighboring crop fields. Objectives of the two-year study were to assess plant composition in field margins and the abundance and distribution of weedy species in neighboring crop fields and determine a relationship between the two ecosystems. Results show no association between plant communities across this managed/unmanaged ecotone.
A project entitled “Strategies for Transition to Organic Systems: Ecological and Economic Indices” was funded by NCDA-NRI in 2001. This is a nested study within the organic system at CEFS that is investigating various strategies, from a biological and economic systems perspective, for making the transition from conventional to organic systems of agricultural production. Parameters being measured include: aboveground biomass of cover crop and cash crop, nutrient/energy flows, soil quality indices (physical, chemical, biological), decomposition, soil microbiological properties, insects, weeds, disease, crop yield and quality, soil microarthropods, soil entomopathogens, and economics. Several research projects are being conducted in this nested study. The objectives of a graduate student in entomology and crop science are to compare beneficial, (predator and parasitoid), and pest insect populations in conventional and organic agricultural systems and to compare beneficial and pest insect populations in an organic cash crop inter-planted with a cover crop to organic cash crop without cover crop treatment. Beneficial and pest insect populations in fall cabbage were sampled weekly in the six treatments, in each of the three NRI plots. Tomato plants were placed weekly in each treatment to determine pest egg parasitism levels and pest larvae were brought back to the lab for rearing to determine parasitism levels. Cabbage yield comparisons between the six treatments were recorded and cabbage head damage due to insects was recorded. A graduate student in horticulture is continuing work started two years ago, which looks at the composition of weed seed populations in fields managed in different ways, and how the compositions have changed over time.

Objectives/Performance Targets

Evaluate the transitional changes that will begin manifestation during years 4-6 on the five, diverse systems: three agricultural, a successional and a plantation forestry system.

2.) Expand the scope of the experiment beyond the initiation phase by nesting other experiments within the larger system.

3.) Strengthen existing innovative educational programs by elaborating the intensive internships in sustainable agriculture for undergraduates, field days, tours, faculty visits and a web site.

Impacts and Contributions/Outcomes

Several presentations have been made at scientific meetings and extension/outreach events to disseminate the results of this work. The systems experiment was featured as part of the national SARE meeting On the Road to Sustainable Agriculture in October of 2002. A national audience of over 500 producers and AG professionals attended the event. A publication entitled Fecal contamination of agricultural soils following hurricane-associated flooding in North Carolina was submitted by Michael J. Casteel from the Department of Environmental Sciences and Engineering in the School of Public Health, the University of North Carolina at Chapel Hill in conjunction with faculty at NCSU and CEFS. They analyzed agricultural soils impacted by floodwaters for bacterial and viral indicators of fecal contamination. The CEFS is continuing to expand its graduate program and several students have or are near to completing their theses. We look forward to a number of publications in the near future.

Publications and Poster Presentations of CEFS Faculty and Students

Barbercheck, M., M. Bell, C. Brownie, N. Creamer, F.Louws, L. King, S. Koenning, S. Hu, M. Linker, P. Mueller, C. Raczkowskie, and M. Wagger. 2001. Soil ecology research at the Center for Environmental Farming Systems. College of Agriculture and Life Sciences. Soil Ecology Society Conference, May 20-23, University of Georgia. Abstracts. Page 33.
Barbercheck, M. Response of Soil Organisms to Conventional and Alternative Agricultural Production Systems . National SARE Conference, October 23-26, 2002, North Carolina
Bell, M.C., M. E. Barbercheck, F.J. Louws, M.G. Wagger. 2000. Quantitative and qualitative indicators of soil quality. Abstract Soil Science Society of America
Annual Meetings.
Brownie, C. M.G._Wagger,_S.V. Woolard, M.E. Barbercheck, M. Bell, N.G. Creamer, S. Hu, L. King, H.M. Linker, F.J. Louws, M.Marra, J.P. Mueller, C.W. Raczkowski. Soil characteristic trends in the first two years of a long term study on the sustainability of agricultural systems. National SARE Conference, October 23-26, 2002, North Carolina
Bullock, LR; Ristaino, JB. 2002. Effect of synthetic and organic soil amendments on southern blight soil microbial communities, and yield of processing tomatoes.
Phytopathology 93(2):181-189; 2002
Burton, M.G. 2003. Careful mowing nearly eliminates sicklepod seedbank return in a short canopy crop. Proceedings of the Northeastern Weed Science Society, Vol. 57. Hyatt Regency, Baltimore, MD, 6-9 January 2003. (poster+published abstract).
Collins, Allysa. Commenced August 1999. M.S. candidate. Characterization of bacterial communities in soil during the transition to organic agriculture. Thesis completed March 18, 2002.
Collins, A.A., D. C. Fargo, and F. J. Louws. Characterization of bacterial communities in soil during the transition to organic agriculture. Phytopathology 92:S16.
Collins, A.A. and F.J. Louws. 2001. Characterization of bacterial communities isolated from soils under diverse management practices. Phytopathology 91: S18.
Creamer, N.G., K.R. Baldwin, F.J. Louws. 1999. A training series for Cooperative Extension Agents in Organic Farming Systems. Hort Technology 2000:675-681.
Creamer, N.G. and J.P. Mueller. 2000. Implementation of Long-term Farming Systems Studies: Challenges and Opportunities. Abstract. HortScience 35:517
Jelinek, S.T., J.P. Mueller, N.G. Creamer, M.G. Burton, and C. Brownie. 2002. Natural Vegetation and Its Influence on Weed Populations in Neighboring Fields. Poster Presentation at Carolina Farm Stewardship Association Sustainable Agriculture Conference. Nov. 15-17. Boone, NC.
Krings, A., M.G. Burton, and A.C. York. 2002. Commelina benghalensis (Commelinaceae) new to North Carolina and an updated key to Carolina congeners. SIDA 20(1):419-422.
Luginbuhl, J-M., y J. P. Mueller. 1998. Crecimiento, producción de hojas, composición química, y ramoneo por caprinos de quatro especies de árboles forrajeros.
III Taller Internacional Silvopastoril “Los Árboles y Arbustos en la Ganaderia”. p 97. 25-27 de noviembre de 1998. Matanzas. Cuba.
Millar, L.C. and M. E. Barbercheck. 2001. Interactions between endemic and introduced entomopathogenic nematodes in conventional-till and no-till corn. Biological Control 22: 235-245.
Millar, L.C. and M. E. Barbercheck. 2002. Effects of tillage practices on entomopathogenic nematodes in a corn agroecosystem. Biological Control 25:1-11.
Moyer, K.A., D.M.H. Watson, K.D. Tungate, J.W. Burton, T.W. Rufty Jr. The involvement of mycorrhizae in nitrogen transfer between crop and weed species. (Poster) 2001 meeting of Weed Science Society of America, Greensboro, N.C.
Moyer, K.A., N.S. Allen and T.W. Rufty, Jr. Aluminum sensitivities of soybean and competing weeds. (Poster) 2001 meeting of American Society of Agronomy, Charlotte, N.C.
Mueller, Barbercheck, Bell, Brownie, Creamer, Hu, King, Linker, Louws, Marra, Raczkowski, Susko, Wagger. 2001 Desarrollo y Implementacion de un Estudio de Sistemas Agricolas al Gran Escala y Larga Duracion. I Simposio Internacional sobre Ganaderia Agroecologica, La Habana, Cuba, 6-8 December, 2001
Mueller, J.P., M. E. Barbercheck , M. Bell, C. Brownie, N.G. Creamer, A. Hitt, S. Hu, L. King, H.M. Linker, F.J. Louws, S. Marlow, M. Marra, C.W. Raczkowski, D.J. Susko M.G. Wagger. 2002. Development and Implementation of a Long-Term Agricultural Systems Study: Challenges and Opportunities. HortTechnology. 12(3):362-368.
Seem, J. 2001. Optimum weed-free period in sweetpotatoes. 2001. Yearbook of the North Carolina Vegetable Growers Association. Greensboro, NC. December 10, 2001.
Seem, Jessica. 2002. Critical Weed-Free Period for ‘Beauregard’ Sweetpotato (Ipomoea batatas) and Weed Seedbank Changes in Response to Transitioning from Conventional to Organic Farming Systems. MS Thesis.
Seem, J. Creamer, NG, Monks, DW. 2003. Critical weed-free period for ‘Beauregard’ sweetpotat (Ipomea batatas). Weed Technology. Accepted for publication.
Sermons SM, JM Chiera, TW Rufty. 2001. Quantification of weed seed morphology. Annual Meeting of the Weed Sci Soc of America, Abstr. p 21.
Stout, R.D., M.G. Burton, H.M. Linker. 2003. Comparison of Two Methods to Estimate Weed Populations in Field-Scale Agriculture. Northeastern Weed Science Society
(Awarded 1st prize for poster contest+ published abstract)
Tu C., S. Hu, S.R. Koenning, and K.R. Barker. 2002. Root-parasitic nematodes impact microbial biomass and nitrogen mineralization in six soils. Abstracts of ASA-CSSA-SSSA 2002 Annual Meetings (CD-ROM version). ASA-CSSA-SSSA, November 10-14, Indianapolis, IN.
Tungate KD DJ Susko TW Rufty. 2002. Reproduction and offspring competitiveness of Senna obtusifolia are influenced by nutrient availability. New Phytologist 154: 661-669.
Tungate KD, KA Moyer, DW Israel, DM Watson, TW Rufty. 2001. Mycorrhizal
Colonization and growth of soybean and competing weed species at different temperatures. Annual Meeting Abstr [CD-ROM]. ASA, CSSA, and SSSA.
Tungate KD DJ Susko TW Rufty. 2000. Seed production and maternal effects with sicklepod grown in a low fertility environment. Canadian Botanical Society Abstracts, June, 2000.
Watson, D. W., S. M. Stringham, S. S. Denning, S. P. Washburn, M. H. Poore, and A. Meier. (In Press). Managing the horn fly, Haematobia irritans (L.), Diptera, Muscidae, using an electric walk-through fly trap. J. Econ. Entomol. Watson DMH, T.W. Rufty. 2001. Impact of flooding on a Glomalean fungal population in an agricultural soil. 3rd International Conference on Mycorrhizas, “Diversity and Integration in Mycorrhizas”. July, 2001. Adelaide, South Australia.
Wossink, Ada and N. Kuminoff. 2002. Organic Agriculture in North-Carolina, NC State Economis, Sept/Oct.
Wossink A., and N. Kuminoff. 2002. Economics of Transition to Organic Agriculture, Poster Presentation. National SARE Conference. October 24, 2002.
Wossink, Ada and Nick Kuminoff, “Economics of Transition to Organic Agriculture”, Poster 54th Annual Crop Protection School, December 12, 2002, McKimmon Conference & Training Center, Raleigh NC.
Zhang W.J., J.S. Wu, C. Tu, and S. Hu. 2002. Microbial activities, biomass and N dynamics in alternative agroecosystems. National SARE Conference: ON THE ROAD TO SUSTAINABLE AGRICULTURE October 23-26, 2002.

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