The Impact of Agricultural Systems on Soil Quality and Sustainability

The Impact of Agricultural Systems on Soil Quality and Sustainability

Summary

Plots in the Long-term Farming Systems Trial at the Center for Environmental Farming Systems were sampled in May, July, and September of 2001, 2002, and 2003 to determine the effects of various production systems on selected soil abiotic and biotic characteristics. No differences were found between systems for field capacity, hydraulic conductivity, plant available water retention and soil microporosity. Bulk density was lowest in the organic system, a system that is tilled for the production of organic crops, and highest in the crop/animal system, a non-tilled environment compacted by the grazing activity of animals. In general, greater CO2 evolution was measured in spring vs. fall, most notably for the perennial agroforestry, pasture, and successional systems. Carbon evolved in the BMP no-tillage treatment was approximately two-fold greater than the conventional tillage system (490 vs. 240 kg C/ha/day) at the spring sampling date and only 18% greater (444 vs 376 kg C/ha/day) by fall. Population densities of nematodes feeding on bacteria and fungi were greater in organic than in conventional treatments. Total entomopathogenic nematode cumulative abundance from 1999-2002 was greater in the BMP no-till, Woodlot and Successional plots than in the BMP contventional till, organic, and pasture plots. 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 treatments. Collembolan abundance was positively correlated with percentage sand and macroporosity (r2 = 0.4) and negatively correlated with percentage clay microporosity (r2 = -0.4). In 2003 and 2004, several presentations were made at scientific meetings and extension/outreach events to disseminate the results of this work. Approximately 500 people were introduced to the concepts and components of soil quality.

Objectives/Performance Targets

Objectives:
1) develop indicators of soil quality for assessing ecological shifts related to sustainability (e.g. biotic and abiotic factors associated with low pest populations, increased crop health and/or tolerance to pest damage, and crop yield/quality)
2 ) determine the impact of agricultural system on selected soil organisms and soil chemical/physical indicators

Accomplishments/Milestones

Soil Physical and Chemical Properties

Soil physical properties were measured on September 19, 2002 in the organic, BMP conventional, BMP no-till, crop/animal (pasture), trees (Black Walnut) and succesional systems. Measurements included soil bulk density, saturated hydraulic conductivity, total porosity, macroporosity, microporosity, plant available water, and field capacity. No differences were found between systems for field capacity, hydraulic conductivity, plant available water retention and soil microporosity. Bulk density was lowest in the organic system, a system that is tilled for the production of organic crops, and highest in the crop/animal system, a non-tilled environment compacted by the grazing activity of animals. No differences in bulk density were found between the no-till, trees and successional systems. The soil total porosity data followed the same trend as the soil bulk density data. Interpretation of the distribution of pore space into macro- and microporosity reveals that changes occurring in total porosity resulted from changes in macroporosity. The hydraulic conductivity trend was consistent with the soil macroporosity data but no significant differences were found between systems. Plans are to continue yearly measurements of these properties on each system.
systems successional, crop/animal integrated, and no-till BMP

Soil chemical (pH, organic C, total N, NO3 and NH4-N), physical(bulk density, infiltration, and water-holding capacity), and biological(CO2 evolution) properties were measured as indicators of soil quality in five diverse agricultural systems from May-June 2002 and again in the fall following crop harvests. Of the parameters measured, the most striking difference between systems occurred with the CO2 data for both sampling dates. In general, greater CO2 evolution was measured in spring vs. fall, most notably for the perennial agroforestry, pasture, and successional systems. Carbon evolved in the BMP no-tillage treatment was approximately two-fold greater than the conventional tillage system (490 vs. 240 kg C/ha/day) at the spring sampling date and only 18% greater (444 vs 376 kg C/ha/day) by fall. The pasture system was similar to the BMP no-tillage treatment in the spring, with intermediate values ranging from 160 to 280 kg C/ha/day observed for organic, crop/animal, agroforestry, and successional systems. Infiltration, measured as the time required for 2.54 cm of water to move into the soil, was notably faster in the organic system during spring and fall sampling periods compared to all other systems and reflects the reliance on cultivation as a weed management tool in organic production. After two years, these results continue to indicate 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.

Nematode communities

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.

Insect-parasitic nematodes and fungi

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. Total entomopathogenic nematode cumulative abundance from 1999-2002 was greater in the BMP no-till, Woodlot and Successional plots than in the BMP contventional till, organic, and pasture plots. S. carpocapsae, which tends to occur near the soil surface, appears to have been most severely affected by soil disturbance – tillage in the organic and conventional tillage treatments, and by compaction in the pasture. H. bacteriophora, which tends to move throughout the soil profile, was more abundant in the BMP conventional till than no-till plots. S. glaseri was equally abundant across all treatments. Insect-parasitic fungi was rarely dectected compared with the detection of insect-parasitic nematodes. Metarhizium anisopliae was more commonly detected than Beauveria bassiana. Detection in all treatmetns was similar, except for the pasture system, in which M. anisopliae was detected at about 2 to 5 times the frequency as in other systems.

Soil arthropods
Microarthropods enhance microbial activity, accelerate decomposition, and mediate transport processes in soil. 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 treatments. This pattern was driven by the abundance of soil mites, which comprised about 70% of the sampled arthropod community. Collembola and all other arthropods comprised about 20 and 10% of the soil arthropod community, respectively. Soil compaction in the pasture system may have contributed to the low numbers of arthropods detected there. Collembolan abundance was positively correlated with percentage sand and macroporosity (r2 = 0.4) and negatively correlated with percentage clay microporosity (r2 = -0.4).
Using multivariate analysis (Fig. 1) 42% of the variation in abundance of soil organisms was explained by the first two dimensions.
Impacts
Time of sampling may affect conclusions as to which soil characteristics are most dominant and or important in measuring soil quality. These results will be used to determine indicators of ecosystem health. Over the last three years differences among the various systems are beginning to be expressed.
Future research may be able to focus on identification of taxa to determine indicator species. Approximately 500 people were introduced to the concepts and components of soil quality.

Impacts and Contributions/Outcomes

Impacts
Time of sampling may affect conclusions as to which soil characteristics are most dominant and or important in measuring soil quality. These results will be used to determine indicators of ecosystem health. Over the last three years differences among the various systems are beginning to be expressed.
Future research may be able to focus on identification of taxa to determine indicator species. Approximately 500 people were introduced to the concepts and components of soil quality.

Contributions/Outcomes
In 2003 and 2004, several presentations were made at scientific meetings and extension/outreach events to disseminate the results of this work.

Publications
Barbercheck, M. and C. Hoy. 2004. Systems Approach to Conservation Biological Control in “Entomophilic Nematology” (P. Grewal, R.-U. Ehlers,eds.) CABI (in press)

Thesis
Bell, M. C. 2002. A Multidisciplinary Approach to Assessing Changes in the Soil Quality of Diverse Farming Systems. Master’s Thesis, North Carolina State University, Raleigh, NC

Presentations

Greenwood, C. M. , Barbercheck, M.Interactions between predators and entomopathogenic nematodes. Entomological Society of America Annual Meeting Cincinnati, Ohio, 26-29 October 2003

Barbercheck, M. Displacement and persistence. Third International Symposium of Entomopathogenic Nematodes and Symbiotic Bacteria. September 4-7, 2003,Arden Shishler Conference Center, Wooster, Ohio

W. ZHANG, H. D. Shew, M. Barbercheck and S. Hu Nematodes and collembola significantly reduce disease incidence caused by the pathogen, Pythium ultimum, in tomato. American Phytopathological Society, Aug. 9-13, 2003. Charlotte, NC

Louws, F.J. Soil Biology and Plant Disease Management. 16 December 2003. For graduate level course in Soils (K. Baldwin PI). Fletcher, NC.

Barbercheck, M. Aug. 13, 2004, The soil food web and soil quality: Letting the soil work for you. Northeast Organic Farming Association Annual Meeting, Amherst, MA

Barbercheck, M Barbercheck, M Feb. 11, 2004, Soil Health, Soil Quality, Impacts on Residual Effects of Pesticide in No-Till. Centre Region Crops Day. Pleasant Gap, PA. 50 attendees (2 women)

Barbercheck, M. Feb. 5, 2004, Soil Quality: Making the Soil Work for You. Southeast Pennsylvania Crops Conferences, Bucks Co. 80 attendees.

Barbercheck, M . Feb. 3, 2004 Soil Quality: Making the Soil Work for You. Southeast Pennsylvania Crops Conferences, Montgomery Co. 200 attendees (10 women)

Barbercheck, M . The role of soil organisms in pest management. 4 March, 2003. PSU Grounds staff in-service, University Park, PA.

Barbercheck, M . Conserving Beneficial Organisms in Soil, PSU Technical Service Pesticide Training, 6 January 2004, PSU

Barbercheck, M . Insect Pest Management in Organic Systems. Lackawanna Co., Scranton, PA, 11 Dec. 2003. 15 attendees (4 women, 1 Asian man, 1 Asian woman)

Barbercheck, M., Mortensen, D. Building Pest Suppressive Soils: Research at Multiple Spatial Scales, USDA Sustainable Ag Lab, Beltsville, MD 26 February 2004

Barbercheck, M, Garling,, L., Seeley, S. Ten reasons why you should buy locally grown food. Penn State Earth Day, 13 April 2003. Invited.

Barbercheck, M. The Impact of Agricultural Practices on Soil Organisms. Ohio State University, Wooster, Entomology Departmental Seminar, 28 January 2003, invited.

Barbercheck, M. Soil Ecology Research. Rodale Institute, 24 January 2003, invited.

Barbercheck, M . Organic Research at PSU. Pennsylvania Certified Organic 2003 Annual Meeting, Dec 10, 2003. Millerstown, Perry Co., 75 attendees.

Barbercheck, M . Agronomy Extension In-Service, Beneficial organisms in agricultural soil, November 20-21, 2003, PSU

Barbercheck, M . Beneficial organisms in agricultural soil. Ag Progress Days, 19-21, 2003. Rock Springs, PA

Barbercheck, M . Creating a Research, Extension and Education Program Focused on Organic Agriculture: Lessons from the Center Environmental Farming Systems. Introduction to Organic Production Workshop. April 1-2, 2003, State College, PA. 70 attendees.

Barbercheck, M., The Soil Food Web. Sustainable Soils Conference, Pittsboro, NC, 27 February 2003. 100 attendees.

Collaborators: