Water quality is and will continue to be the most important environmental issue facing the Illinois agricultural community. With the advent of Total Maximum Daily Loads (TMDLs), the Gulf Hypoxia issue, and impending nutrients standards for all surface waters, it is imperative that the agricultural community take a proactive approach in addressing water quality issues at the local watershed level. Thus, it is essential that the environmental fate of fertilizers be documented at both the plot- and watershed-scales when Best Management Practices (BMP’s) such as riparian buffers are implemented. Documenting the effectiveness of BMPs for fertilizer attenuation will provide support for the agricultural community allowing them to maintain current fertilizer application rates, which will benefit both the producer in terms of production and the fertilizer industry in terms of sales. The protection of water quality through the voluntary adoption of BMPs would reduce the possibility of future mandated fertilizer application restrictions in the state.
Specific objectives of the project are as follows:
Southern Illinois University Carbondale (SIUC) owns several hundred acres of farmland near campus, which is primarily managed as row crop and pasture land. Thus, the property provides an excellent setting for the establishment of long-term riparian buffer research sites, and provides the possibility for future riparian buffer manipulations. The proximity to the University also provides an excellent opportunity to use the property for demonstration and outreach purposes.
On SIUC farms, 3 small (~100 ha), row-crop dominated watersheds were selected for long-term water quality and quantity monitoring. At each watershed outlet, a Parshall flume, a gauging station, and an automatic water sampler have been installed to monitor stream discharge and water quality. Specific water quality parameters measured include nitrate, ammonium, phosphate, total suspended solids, pH, and specific conductance. Samples are being collected following storm events exceeding 1.25 cm of rainfall. Data will be analyzed using a paired watershed approach, where one watershed will be identified as a control watershed (no riparian buffer) and the remaining two watersheds will serve as treatment watersheds (forested buffer and giant cane buffer). Watersheds have been cleared of all riparian vegetation and planted with row crops to the stream margin to determine the water quality relationships for the calibration period, which will span a 3 year period. During the calibration period, volunteer woody species that become established in the riparian areas will be removed via mechanical methods. Following the calibration period, one treatment watershed will be planted with a 10 m wide giant cane buffer along both sides of the stream and the other treatment watershed’s riparian zone will be planted with a 10 m wide suite of mixed hardwood species on each side of the stream.
A plot-scale experiment was designed to test the nutrient attenuation capabilities of common riparian buffer vegetation species and their associated soils. Twelve 1x10m surface runoff plots were established during the summer of 2008 planted with giant cane (Arundinaria gigantea (Walt) Muhl.), orchardgrass (Dactylis glomerata L.), and Kentucky bluegrass (Poa pratensis L.) on August 8, 2008. Three replicates of each vegetation, and 1 corresponding control plot was established, which were cleared of all vegetation to help account for soil variability and nutrient binding. A retaining material that impedes water was used to delineate plot boundaries and will allow the vegetative plots to be subjected to a controlled volume of nutrient-laden overland flow. Various nutrient solutions will be applied to the plots under simulated rainfall in the spring of 2009. Input and output concentrations of nutrients will be assessed for each plot, and concentrations will be documented at 2 meter intervals throughout the plot length. Samples will be collected at intervals during the simulated rainfall event. Within each plot, soil characteristics (e.g., bulk density, particle size, and infiltration rates) will also be assessed to determine the effect that soil physical characteristics have on nutrient attenuation.
Three areas with cropping history will be selected, that will coincide with the location of the watershed collecting runoff devices. The treatments consist of two types of nitrogen fertilizer: slow release N fertilizer (SRF) and urea, and a control with no N application will be included. The N application to corn will be 60, 120, 180, 240 lb acre-1.
We will have a completely randomized block design (CRBD) with four replications. Minimum plot size will be 6 rows x 40' with the center three rows harvested for yield and plant measurements to avoid border effect. Corn will be planted the following year and no rotation will be evaluated in this study, to minimize possible complex interactions within the study. Overland flow collectors and porous cup water lysimeters will be installed in each plot at a depth of 4 ft. The water samples leached will be collected on the field and brought to the laboratory for nitrate (NO3-) analysis. The data collected in each site will be correlated with the data obtained from the runoff data collected in previous objectives.
Baseline water chemistry data have been collected since January 8, 2007. To date, 32, 28, and 22 rainfall events have been collected in the 3 watersheds. Preliminary data collected from the runoff events are summarized in table 1. These data will be used in a paired-watershed approach to develop relationships among the three watersheds.
Plot data from a slow release fertilizer (SRF) study performed during the 2007 and 2008 growing season are summarized in table 2. These data will be used to determine the fertilization rates to be used in a watershed comparison study. Based on yield results between 120 and 160 lbs/ac of SRF will be applied to the treatment watershed (Figure 1). Overland flow and soil water will be collected from these watersheds in 2009 and 2010. During both years of the study corn will be planted in back-to-back years.
The watershed demonstration sites have been used for multiple class exercises and are available to demonstrate the utility of BMPs in agricultural landscapes. A website has been developed to provide more detail and follow the progress of the project (http://mypage.siu.edu/jschoon/Farms%20Homepage.htm). In the future, interpretive materials will be available that provide information on the project’s objectives, methods and findings.
To achieve objective 3 and 4 it was essential to establish a source of giant cane propagules, thus cane rhizomes were collected in the spring of 2008 and planted to create a nursery for future cane buffer plantings associated with the project. The giant cane nursery is located on a 1 acre tract at SIUC farms and will also be used as a demonstration area.
Year 1 was an active year for equipment installation and baseline data collection. Data for watershed calibrations are continually being collected and will continue through 2010. The next 2 years will focus on the calibration of the watersheds and performing the fertilizer runoff trials at the plot scale. Also, the two experimental watersheds will be instrumented with lysimeters and overland flow collectors, planted with corn for two consecutive years, and have slow release fertilizers applied to the treatment watershed. These watersheds will be sampled for surface and subsurface water quality following significant rainfall events.