The production of flowering oilseeds along highway right-of-ways provides land managers with a unique opportunity to meet safety and vegetation management objectives while providing enhance roadside aesthetics for motorists. Additionally, these operations provide an economically valuable grain commodity that can either be used to offset the management costs or provide a feedstock that can be used in the biodiesel production process. Examples of flowering oilseeds that provide aesthetic value and vegetable oils for biodiesel production are canola, camelina, mustard varieties, safflower, and sunflowers. This two-year research effort, sponsored by the North Carolina Department of Transportation (NCDOT) investigated the cultivation of oilseed crops along North Carolina highway rights-of-way (ROWs) which would ultimately be destined for conversion to biodiesel and use in their fleet of motor vehicles. While various oilseed crops have proven to be viable feedstock for renewable fuel production in the United States, their suitability for production in the highly eroded, highly compacted, low nutrient soils of North Carolina highway ROWs has not been evaluated. Therefore, the goal of the project was to evaluate the feasibility of maintaining a sustainable oilseed crop production system on these non-agricultural soils of NCDOT highway ROWs for utilization as a source of feedstock for producing the biodiesel fuel. To achieve this goal, objectives were established to (1) evaluate oilseed crop requirements and eligibility for production based on North Carolina¿s climatic conditions and highway rights-of-way characteristics; (2) perform a series of plot trials to select an optimal tillage method (3) develop a GIS program to quantify and map eligible NCDOT highway ROW acreage based on average seasonal rainfall and temperature observations, ROW widths and slopes, highway characteristics and adjacent traffic volumes, and wildlife and motorist safety regulations.
Beginning in early June 2009 and concluding in June mid 2011, research was conducted in five locations in North Carolina. Experimental sites were established in Faison, Knightdale, Mount Airy, Pittsboro, and Rutherfordton. Depending upon location, canola (Brassica napus L.), safflower ( Carthamus tinctorius ), and sunflower (Helianthus annuus) were cultivated in rotation under one or three different tillage methods (maximum tillage, minimum tillage, and no-till). Seed yields were evaluated to determine possible main and interaction effects among tillage, location, and year of cultivation (initial cultivation or subsequent cultivation) on crop productivity in a three by three by two factorial experiment. For both 2009 and 2010 planting seasons, year and site displayed significant effects on seed yield, while tillage treatment showed a significant influence only when comparing maximum to no-tillage and minimum to no-tillage treatments in 2010 plantings. Interactions of site × tillage, tillage × year, and site × tillage × year were not found to have significant effect in either planting season; however, the effects of site × year interactions were significant, and all plots observed significantly higher yields in the second year of harvest as compared with initial cultivations. In 2009, the maximum tillage treatment produced the highest average yields of 1108 lb ac-1(1241 kg ha-1) followed by minimum tillage and no-till, at 827 lb ac-1 (926 kg ha-1) and 766 lb ac-1 (858 kg ha-1), respectively (Table 2.4). However, in the second year, the comparative intensity of productive effects from maximum tillage was lower, and plots cultivated under the minimum tillage treatment resulted in the highest average yields of 2409 lb ac-1 (2698 kg ha-1), followed sequentially by maximum tillage and no-tillage, at 2399 lb ac-1 (2687 kg ha-1) and 1750 lb ac-1(1906 kg ha-1), respectively. Recommendation of an initial deep tillage treatment followed by subsequent no-till practices for canola cultivation was supported by an evaluation of economics typical of these tillage practices and a lack of significant difference between yields observed from maximum versus minimum tillage. Additional investigation is needed to verify that the increased productivity in subsequent seasons could be attributed wholly to productive effects of a single deep tillage treatment on soil structure and reinforced by ability of canola¿s rooting system to break up compaction and return nutrients to the soil. Based upon a derived equation for ROW width, GIS analysis was utilized in identifying 14, 962 mi (24,079 km) of eligible ROW, thus totaling approximately 18,136 ac (7,340 ha) of total eligible land base.
