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Water Quality Evaluation of Long-Term Organic and Conventional Vegetable Production under Conversation and Conventional Tillage


The goal of this project is to measure and model nonpoint source pollution (nitrogen (N), phosphorus (P) and sediment) associated with organic and conventional vegetable farming systems under different tillage practices in the Appalachian Mountains of North Carolina. The objectives of the proposal are seven fold: <OL> <LI>evaluate nutrient and sediment concentrations and loads in surface runoff, and groundwater nutrient concentrations from long-term conventional and organic systems, <LI>evaluate nutrient and sediment concentrations and loads from surface runoff and groundwater nutrient concentrations from long-term tillage (conservation and conventional) under conventional and organic systems, <LI>evaluate soil organic matter (total and particulate), cover crop biomass and N in order to relate changes in soil properties to nutrient and sediment runoff, <LI> evaluate crop yield, nitrogen uptake and calculate nitrogen use efficiency of the different treatments, <LI>evaluate the predictive performance of the Agricultural Policy Environmental Extender (APEX) model, <LI> transmit study results to organic and conventional producers, state agency personnel, regional and national audiences (extension), <LI>transmit study results to undergraduate students and interns (students), and the agricultural community as a whole (education). </OL>Extension outputs include: Stakeholder involvement through a board that will communicate yearly through Elluminate Live! conferencing software supported by NC State University. Using eOrganic, we will create information-rich summaries of our and additional water quality related data that will be disseminated throughout the organic agriculture community quickly and efficiently. We will provide information about 1) cover crops, 2) no-till and reduced tillage in organic agriculture, and 3) policies farmers should be aware of related to water quality in agricultural systems at the annual Carolina Farm Stewardship workshop and to the organic grain producers at the annual North Carolina Corn Growers Association. Additional presentations will occur in North and South Carolina to vegetable growers, at the annual meeting of the American Society of Horticultural Science, at the Summer Vegetable Field Day at Mountain Horticultural Crops Research Station, the NC Crop Protection Association, and the NC Plant Food Association. State-based fact sheet will be produced for North Carolina Producers and distributed at field days and grower meetings. Information from this project will be incorporated into information on conservation effectiveness derived from the national CSREES-CEAP project. A workshop will be organized for small and limited resource farmers to promote adoption of the appropriate tillage system.<P> Teaching outputs include: We will provide a 1-credit course on water quality to graduate students who are working in the realm of organic farming systems or agroecology to enhance their understanding of the relationship between agricultural production and nonpoint source pollution. In addition a one hour lecture will be delivered, Soil Agroecology (SSC 495).

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Non-Technical Summary: Organic production of foods has grown dramatically over the last 20 years. However, few studies have been conducted to demonstrate the benefits or risk of organic production to water quality relative to conventional systems of food production. This experiment will compare a conventional system with an organic system. Information on water quality and yields will be collected. We will grow continuous corn with separate covers (crimson clover - organic production and wheat - conventional production) under conventional and conservation tillage conditions. Sediment and nutrient data will be collected from runoff waters and we will also measure the nutrients in the groundwater under the plots. Yields will be compared to determine if one system outproduces the other. Based on the information we receive, we will work with farm organizations in North Carolina and throughout the southeast to convey these results. In addition, we work with undergraduate students to link water quality and different types of production. <P> Approach: Agricultural treatments include 1) organic management + conservation tillage, 2) organic management + conventional tillage, 3) conventional management + conservation tillage, 4) conventional management + conventional tillage, and 5) control - treatment is plowed, disked, and planted and there are no additional inputs of fertilizer or pesticides. Only cover crops and source of nutrients will differ in the organic and conventional systems in order to minimize confounding of water quality data with crops cropping systems. Crimson clover is the cover of choice for organic producers and wheat is the cover crop of choice by producers of conventional systems. We will apply the same amount of N to both treatments: 200 lb N ac-1, either as NH4NO3 (conventional system) or dairy manure (manure + urine+ water) and N derived from crimson clover (organic system). We will count sweet corn populations and take two recorded harvests to remove all marketable fruit. We will also measure biomass production of the stover. Tissue sample from both the stover and fruit will be harvested and analyzed for total N. We will obtain total soil C measurements at the outset of the experiment and once annually for the duration of the project using the dry combustion. Standard soil tests will also be carried out at this time including all major soil macro- and micro-nutrients, cation exchange capacity, base saturation and pH. We will also determine levels of particulate organic matter leaving the treatment plots in each rain event in sediment. The proposed monitoring will characterize total loads of N, P, and sediment. Plots will be delineated via landscape edging with one end buried at least 2 inches underground in order to isolate the surface water hydrology of each plot. At the downslope end of each plot, a diversion or collection trough will be installed to funnel the runoff to a central outlet point. A monitoring station will be established at the outlet point of each plot and collected samples will be analyzed for TN, NO3-N, and NH4-N. Dissolved organic N will be calculated as the difference between TN and NO3-N + NH4-N. The nonacidified sample will be analyzed for total suspended solids and PO4-P. Based on initial data, one groundwater monitoring well will be established in each plot that is screened from the top of the groundwater to at least 0.6m below and samples will be analyzed for NO3-N, PO4-P, Cl, TN and DOC. The data will be analyzed to determine if management activities directly impacted water quality. Statistical analysis for the water quality and yield data will be performed using the SAS software program. PROC MIXED will probably be used and we will determine the normality of the data to determine if transformations are required.

Osmond, Deanna
North Carolina State University
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