Maintenance Program for
|Objectives and Expected Outputs|
|Expected Outputs:||Besides providing continuing support for
the landowners in adopting conservation tillage/cropping practices, this
project will provide an ongoing record of the water quality and quantity
as well as the agricultural practices on these watersheds.
NOTE: a continuation of Project 4.1a / Project 4.1b / Project 4.1c.
|Type:||Contribution Agreement, Conservation Authority|
|Status:||Available March 1998|
In Southwestern Ontario, conservation farming systems were promoted as a method of reducing soil degradation on agricultural land. By arresting soil erosion, conservation farming systems could potentially reduce sediment and phosphorous delivery to surface drainage systems. The reduction in sediment and phosphorous in runoff from the agricultural land would ultimately reduce sediment and phosphorous loading to the Great Lakes Ecosystem.
To demonstrate the effectiveness of conservation systems, the Paired Watershed Study (PWS) was created and implemented in 1987 as a sub-program of the Soil and Water Environmental Enhancement Program (SWEEP). In the PWS, farmers within demonstration subwatersheds were encouraged to adopt conservation farming systems while farmers within control subwatersheds were encouraged to continue their existing farm practices. Water quality was monitored at the outlet of each subwatershed to detect changes resulting from the conservation practices.
At the end of the SWEEP Program, monitoring in the Paired Watersheds resumed through funding provided by the Green Plan. The study was revised to include Paired Watersheds at the headwaters of Kintore Creek. The Essex Region and Kettle Creek Paired Watersheds were retained from the original SWEEP PWS Study. The monitoring, technical assistance and landowner liaison were managed by the Upper Thames River, Essex Region and Kettle Creek Conservation Authorities respectively.
The study was designed to determine the impact of conservation farming systems on water quality at the subwatershed scale by measuring soil and nutrient loss as suspended solids and total phosphorous concentration in the surface drainage system. To facilitate the study, the Conservation Authorities encouraged the farmers to continue their level of adoption of conservation farming practices which were attained at the end of the SWEEP Program. Monitoring included precipitation, air temperature, agricultural practices, water quality and water quantity. The data collected was shared with a number of other research projects sited within the watersheds.
The Paired Watershed Study areas were representative of agricultural landscapes in Southwestern Ontario. At Kintore, dairy, beef and swine operations were mixed with cash crop farming. Well drained silt loam soils covered rolling terrain where the surface slope was generally 5%. Extensive vegetated buffer strips lined both channels where groundwater supported continuous discharge. In the Kettle Creek Paired Watersheds, mixed farming operations included dairy, swine, poultry, cash crop and vegetables. Moderate to poorly drained silt loam and silty-clay loam soils existed on surface slopes of 2 to 5%. In the Essex Region Paired Watersheds, intensive cash crop systems account for the majority of farming activity in both subwatersheds. Poorly drained clay soil was drained through extensive sub-surface tile systems. The surface drainage systems in the Essex and Kettle Paired Watersheds were poorly supported by groundwater and typically remained dry through the summer months.
The three paired watersheds had distinctly different climatic characteristics as a result of their geographic locations. Climate in the Essex Paired Watersheds was moderated by the proximity to Lake St. Clair, Lake Erie and to a certain extent by the slightly more southerly latitude. The Kintore Paired Watersheds were located in the traditional snow belt area of Southern Ontario where 15 to 20 centimetres of snow cover remain from mid December through late February. The Kettle Paired Watersheds were southwest of the snow belt area and significant winter snow accumulation was uncommon.
Climate, especially precipitation intensity, frequency and duration was extremely variable during the Paired Watershed Study. Snow accumulation prevented runoff by absorbing rainfall during the winter months. At other times, rainfall on frozen ground produced significant runoff, soil erosion and sediment delivery for brief periods before the temperature fell below freezing and the rain changed to snow. Intense rainfall during the peak tillage period in the spring or before a protective crop canopy existed, produced extreme concentration values for suspended solids and total phosphorous in all three subwatersheds.
The climatic conditions during the study period provided an opportunity to monitor water quality during short-term deviations from the long-term normals. In the Kintore and Kettle Creek Paired Watersheds, two years of the study had near normal total annual precipitation while one year was slightly wetter than normal, and one was slightly drier. In the Essex Region Paired Watersheds, all four years were dry. Colder than normal, warmer than normal and normal mean monthly temperatures were measured during the study which produced a variety of runoff conditions. The climatic conditions affected the timing and method of tillage or planting, and crop yield.
In the Three Paired Watersheds, the farmers in the demonstration subwatersheds have made a long-term commitment to conservation farming systems. Each has adopted the methods which have proven practical and effective on their respective farms. The farmers in the control subwatershed demonstrated their interest in conservation farming methods through limited experimentation during the course of this study.
Throughout the study, the farmers were requested to maintain their level of adoption of conservation practices to facilitate the measurement of any changes in water quality which could be attributed to conservation farming systems. Over the course of the study, there were fluctuations in the percentage of each subwatershed which was treated with each type of conservation tillage equipment. These fluctuations mainly resulted from adverse climatic conditions and therefore unsuitable soil conditions. Also, certain tillage methods were preferred to handle certain crop residue types which resulted in fluctuations as different stages were reached in a crop rotation system. There was a marked increase in no-till planting in the Kettle Creek control subwatershed for two seasons which coincided with the increase in soybean acreage.
At the conclusion of the PWS, it was realized crop yield information from participating landowners would prove a useful addition to the existing tillage and water quality information. While not specifically included or required as part of the original monitoring program, crop yield data has since been collected and added to this report to increase the utility of information for related research.
Hydraulic yield from the subwatersheds fluctuated according to the amount of input but also in response to the volume of water in storage. The results did not clearly indicate that conservation farming practices were affecting hydraulic yield, water movement or storage within the subwatersheds. Yield was always greater in the first quarter of each year when evaporation, infiltration and plant uptake were minimal.
For water quality parameters monitored during base flow conditions, inter-quartile ranges were established which can be used for comparison with future sample results. The majority of sample results will fall within the inter-quartile range and values outside the range should be further examined or explained. Conservation farming practices were not expected to make a significant change in the water quality during base flow conditions.
In general, the water quality during winter thaw, spring melt or event flow had lower suspended solids and total phosphorous concentrations in the Kintore Creek demonstration subwatershed drainage system (compared to the control subwatershed). The other two Paired Watersheds exhibited more variable results. The difference in water quality between the Kintore demonstration and control subwatersheds may not be directly attributed to the tillage practices. When comparing practices in the demonstration and control , the control subwatershed actually had more area under conservation management than the demonstration. The difference in water quality may result from the erosion control structures in the demonstration subwatershed. The active agricultural area, and therefore the area which could be more easily eroded was much greater in the demonstration subwatershed, yet water quality was generally better in this subwatershed.
In the Kintore Creek Paired Watersheds, the peak concentration of suspended solids was lower in the demonstration subwatershed in 28 of 38 storm event sample sets. Peak concentration was often an order of magnitude lower in the demonstration subwatershed samples. Total phosphorous was lower in 50% of the demonstration subwatershed event samples. In the Essex Region and Kettle Creek Paired Watersheds, peak concentrations of suspended solids and total phosphorous occurred more frequently in the control subwatershed. The peak concentration for suspended solids was always in the same order of magnitude in both subwatersheds.
In the Kettle Creek Paired Watersheds, a small wetland area upstream of the outlet monitoring station in the control subwatershed may be affecting the sample results. However, during event flows there appeared to be insufficient retention time for water quality improvements to occur. The water quality data would suggest that runoff from the control subwatershed was actually carrying less solids and phosphorous away from the agricultural land during some storm events.
In the Essex Region Paired Watersheds, samples from both subwatershed outlets had very poor water quality. The peak concentration of suspended solids exceeded 2000 mg/L at both outlets and total phosphorous was 2.4 mg/L or 120 times greater than Provincial Guidelines. The water quality data would suggest that runoff from the control subwatershed was actually carrying less solids and phosphorous away from the agricultural land. No-till practices may be contributing phosphorus to surface runoff but a more likely source of phosphorous is the infiltration water which leaches phosphorous from the soil before entering the extensive sub-surface drainage system.
The impact of conservation farming practices on water quality could not be clearly demonstrated at the subwatershed scale. Analysis of the data did not indicate a measurable benefit resulting from the continued adoption of conservation practices but at the same time no negative impact was observed.
Last Updated: May 17, 2011 11:22:56 AM