2013 Annual Report for LS12-247
CEFS Long-Term Systems Research: Providing the Building Blocks for Resilient Food Production Systems
Summary
The Long-Term Farming System Research trial (FSRU) at the Center for Environmental Farming Systems (CEFS) was initiated in 1998 and comprises more than 200 acres with 5 different systems replicated 3 times. The objectives for initiating this trial 13 years ago were to research: 1) how the various systems impact long-term sustainability of soil and water resources, 2) whether some systems are more resilient to perturbations in weather, input and market prices, and 3) how the systems impact biodiversity, wildlife, pest dynamics and the ecological services of farmland. Our study is designed to provide a better understanding of how different systems interact with and impact the natural resource base and economic viability of farms, as well as identify alternative approaches with potential for synergistic effects, such as diversification, access to direct markets, and environmental conservation.
Over time the FSRU systems experiment has become irreplaceably unique for several reasons. First is the comprehensive nature of the systems being studied and their relevancy in the South. Second, the scale (200 acres) and large plot size gives us the ability to study important production system dynamics (e.g., insect and disease management) that others cannot, making our results more relevant to producers. We are also a model of interinstitutional collaboration with involvement of various departments and colleges at each 1890 and 1862 Land Grant university, the NC Department of Agriculture and Consumer Services, and NGOs as diverse as Carolina Farm Stewardship Association and the NC Farm Bureau. Our systems experiment has also integrated outreach at every level with farmer involvement in both research and educational programming. These funds will set our project on a path of long-term sustainability at a critical time as the state undergoes major budget cuts that put the experiment at risk. The NC Department of Agriculture and both universities are cutting personnel and operating support. Short-term grant funding has been indispensable with starting this project, but after 13 years of piecing together support we have learned that maintaining the core components of a systems trial is extremely difficult with sporadic funding.
We are also preparing the FSRU for a new future. Half of our advisory board are new members of CEFS. Their guidance on what is the current thinking of the farm community lends new vitality to our work. Similarly, retirements at the university are at the highest rate in decades. Eight of the faculty involved with this grant are new hires and were not involved with the establishment of the FSRU. This experiment is key to recruiting these faculty to work in sustainable agriculture.
Objectives/Performance Targets
Objective 1: Quantify the greenhouse gas emissions and soil C and N in three organic and tillage management regimes and three paralleled conventional systems.
There is a dearth of information regarding N2O emissions in agricultural soils of the SE US coastal plains. Organic and reduced tillage are believed to reduce GHG emissions and promote soil C and N sequestration. However, lack of long-term field data critically constrains our prediction of the net potential of C sequestration and GHG mitigation.
Objective 2: Determine the impact of invertebrates on residue decomposition and soil C stabilization.
Populations and activities of soil invertebrates such as earthworms, nematodes, mites and collembolans are often higher in organic and reduced or no-tillage systems (Beare et al. 1992; Overstreet et al. 2010; Rahmann 2011). These organisms play important roles in residue decomposition and soil C turnover and stabilization as well as in nutrient release from microbial biomass. Yet, their functions have rarely been determined in field.
Objective 3: Assess the effects of AM fungi on soil aggregation and N retention in organic systems.
Experimental evidence has shown that agricultural practices, such as tillage to diminish AM extra-radical hyphae abundance and root colonization (Kabir et al. 1997), and reduce AM fungal species composition and abundance (Douds et al. 1995) and elimination of synthetic chemicals (fungicides in particular) in organic systems should also reduce the disruption of AM fungal hyphae (Gosling et al. 2006). Yet few have examined how various long-term agriculture systems can affect AM impacts on C and N dynamics.
Objective 4: Ascertain the role of cover crops and weeds in mediating soil N availability
The implications of cover cropping and weeds on N dynamics can be profound. Each flush of weeds results in substantial uptake of N that is temporarily immobilized in weed seedling biomass (Bast 2012). The N does not remain there long. These young tissues decompose rapidly after cultivation, releasing N back into the soil (Bast 2012). During those first 2 months, multiple weed-mediated N cycles serve to keep inorganic N from accumulating in the soil. These cycles could result in either increased or decreased rates of N loss from the system overall.
Most N loss occurs early in a cropping cycle when then crop is young and does not need substantial amounts of N yet for growth. Row crops, such as corn, are particularly ineffective due to the wide between row spacing of plants. Organic corn in North Carolina is grown on row spacings between 30” and 38”. Weeds that emerge between rows are taking up N that could be lost to leaching. The Southeast is particularly susceptible to early season losses because of sandy soils and large rain events (Hubbard & Sheridan 1989). Conventional systems that include preemergence herbicides do not develop the large weed flushes that characterize organic systems.
Objective 5: Education and outreach through developing new curricula on greenhouse gases and agriculture for student training and stakeholders
Despite the public nature of the greenhouse emissions debates, few curricula have been established for engaging stakeholders and students in how these issues affect agriculture. An iterative process is needed that draws on farmer/student concerns and regional differences in farmer practices. Curriculum development will have the direct input of these groups during the first year of the project. Contrary to popular opinion, a majority of farmers believe climate change is occurring in some regions (Arbuckle et al. 2011).
Accomplishments/Milestones
Labile Organic Matter Drivers of Nitrous Oxide Production in Organic and Conventional Cropping Systems: Peyton Ginakes and Julie Grossman
We measured three fractions of soil LOM among four treatments after amendments (manure in organic, UAN fertilizer in conventional). Figure 1 shows that potassium permanganate oxidizable carbon (POX-C) increased with decreasing tillage among organic treatments, while no-till management in the conventional treatment maintained residual LOM despite receiving no organic inputs. A similar trend is followed by microbial biomass carbon and nitrogen (MB-C and MB-N).
Fungal Potential in Soil Nitrous Oxide Production and its pH and Moisture Dependence in Diverse Managed Ecosystems: Huaihai Chen, Nape Mothapo, and Wei Shi
Fungal ability of N2O production has been increasingly documented, yet its ecological importance and controlling factors remains unclear. In this study, the relative contribution of fungi versus bacteria to soil N2O production was examined in five ecosystems, including conventional farming (CON), organic farming (ORG), integrated crop-livestock system (ICL), plantation forestry (PF), and abandoned arable field subjected to natural succession (SUCC). A laboratory microcosm experiment was conducted to measure soil N2O production at 90% water-filled pore space (WFPS) in the antibiotic-free soil as well as soil amended with streptomycin, cycloheximide, or both. While soil N2O production rates differed significantly among the five systems, fungal contribution accounted consistently for > 30% of total soil N2O production. Fungal produced more N2O than bacteria in PF, whereas both made comparable contributions in other four systems. Moisture effects were assessed under six levels of water-filled pore space (WFPS), ranging from 65-90%. Effects of pH were questioned using five levels of pH from 4.0-9.0 after soils were kept at the respective pH condition for one week. Irrespective of antibiotic treatments, soil N2O fluxes increased with WFPS and peaked at ~ 80%, indicating that both fungi and bacteria preferred more anoxic conditions for N2O production. However, fungal-to-bacterial N2O production ratio was inversely related to soil WFPS. Both fungi and bacteria preferred neutral and slight alkaline conditions for N2O production, but fungi contributed more compared to bacteria under acidic conditions. Thus, the ratio of fungal-to-bacterial contribution was negatively correlated with soil pH. Real-time PCR of 16S rDNA, ITS rDNA, norB, nirK, nirS, and nosZ also showed that fungal abundance was greater under acidic conditions, whereas bacterial and denitrifier ones were lower. Our result indicated that fungi could play an important role in soil N2O production in diverse ecosystems and soil pH was a critical control factor.
Determine the impact of invertebrates on residue decomposition and soil C stabilization: Yasmin Cardoza and David Orr
Five types of herbivorous insects were consistently present in large enough numbers across the crop production systems sampled. These included aphids, corn earworms, European corn borers, brown stink bugs, leaf hoppers, and chinch bugs. Herbivore incidence was affected by production system. For example, aphids were by far most prevalent in the crop-animal rotation system and lowest in the organic reduced till system (Fig 2). Data for other herbivores types is currently being processed.
Natural enemy samples were predominated by spiders (Fig 3), but also included ladybugs, green lacewings and predatory bugs in the genera Orius and Geocoris. Presence and incidence of natural enemies was also affected by production system. For example, spider incidence was highest in the crop-animal and organic clean till systems and lowest in the organic reduced till system (Fig 2). Data for other herbivores types is currently being processed.
Contrary to our expectations, the predator/prey ratio was substantially higher in both conventional systems compared to the organic systems and was lowest in the crop-animal rotation system (Fig 4).
Impacts and Contributions/Outcomes
Findings from the Farming Systems Research Unit are being utilized in agricultural policy discussions by many groups. The no-till work is highlighted on the national NRCS website: http://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/health/?cid=stelprdb1245890
Our greenhouse gas results are being shared with Environmental Defense fund in their efforts to model N2O emissions for agriculture in North America. Multiple scientists on this project collaborated in the Abundance Foundation's climate change conferences held in North Carolina in 2013 and 2014.
Multiple field days emanate from the FSRU annually, including the Organic Grains Field Day, the Carolina Organic Commodities and Livestock Conference, Small Farms Week, and the Carolina Meat Conference. Changes in education, management, and profitability from attendees at these events is being monitored and quantified for the final report.
