Local case studies to reduce soil erosion
As part of our Six Streams Initiative, the Bruce Peninsula Biosphere Association is working with local farmers to reduce soil erosion on the Bruce Peninsula’s agricultural lands. Together we are developing demonstration projects to test new agricultural practices that are designed to improve water quality and habitat in nearby streams and lakes, maintain healthy and productive soils on the field, and increase the resilience of farm operations to extreme weather events caused by a changing a climate.
This project has been funded by the Ontario Soil and Crop Improvement Association (www.ontariosoilcrop.org) and the Ontario Trillium Foundation (www.otf.ca).
CASE STUDY 1:
Unlike conventional tillage which leaves the soil bare and prone to erosion, conservation tillage is any tillage practice that leaves crop residue on the soil surface to control erosion on agricultural fields. The residue helps to improve water quality by slowing surface runoff water and allowing it to infiltrate into the soil instead of flowing into nearby streams. With more residue on the field and less soil disturbance from tillage equipment, conservation tillage also helps to maintain healthy soils by reducing soil loss and increasing organic matter and moisture retention. Although there are other types of conservation tillage, this case study focuses on no-till and minimum-till practices. No-till (or direct drilling) is the practice of planting without any seedbed preparation which leaves the maximum amount of residue on the soil surface, while minimum-till involves some seedbed preparation but does not turn the soil over during tillage and leaves a minimum of 30% residue on the surface.
In 2017, two adjacent tile-drained fields located southeast of Ferndale in the headwaters of Judges Creek will be used to compare no-till and minimum-till practices. These 30-acre fields will be spring planted with oats, however, seed will be applied in one field using a no-till drill with no seed preparation and a wavy coulter blade will be used to provide minimal tillage on the other field.
The following methods will be used to assess the effectiveness of no-till and minimum-till practices:
water samples will be collected at each drain outlet during significant rain events to compare phosphorus, nitrate and sediment concentrations coming off the fields
vegetation sampling quadrats will be used to compare impacts of tillage practices on weed abundance during emergence in the spring
crop yields will be measured after harvest to compare impacts of tillage practices on productivity and an analysis of the net income will also be calculated based on yields and overall costs
soil moisture will be visually assessed through crop presentation (wilting), and organic matter will be measured at the onset and end of the growing season with the involvement of local high school students
CASE STUDY 2:
Water and Sediment Control Basins
A water and sediment control basin (WASCoB) is an earthen embankment or berm constructed across the slope of a field to manage surface runoff water. These structures are designed to intercept surface runoff water before it reaches an adjacent watercourse, temporarily collecting the water and allowing it to slowly drain back into the soil or through a piped outlet. This provides time for soil particles and nutrients to settle and remain on the field, and it also protects adjacent streams from bank erosion caused by high volumes of water during severe weather events.
In 2016, a WASCoB was constructed on a field located in the headwaters of Judges Creek, where ongoing sheet erosion has resulted in the loss of productive topsoil on the field. The WASCoB covers an area of 0.25ha and was designed to detain water from an 11.1ha drainage area in the field.
The following methods will be used to assess the effectiveness of WASCoBs:
water samples will be collected at the inflow and outflow of the WASCoB ponding area during significant rain events to compare phosphorus, nitrate and sediment concentrations
the volume of water and retention time in the WASCoB during significant rain events will be calculated based on water depth and dimensions of the ponding area and by measuring the peak flows at the basin inflow and outflow
soil grid samples will be collected in one acre of the field to determine changes in soil fertility by comparing cation exchange capacity and organic matter with previous years
crop yields will be measured after harvest to compare with previous years and to estimated yields determined by pre-installation soil fertility measures
Location and area of WASCOB and its drainage area
Aerial view of WASCOB after completion
Ponding area outflow drain
Surveying the WASCOB site before construction
CASE STUDY 3:
Controlled drainage is a practice that allows farmers to manage water table levels and soil moisture in a tile drained field. It is similar to traditional tile drainage except that the tile outflow is intercepted by a water control structure that allows the water table in a field to be adjusted by adding or removing stop logs within the structure. Removal of the stop logs allows unrestricted drainage during the planting and harvesting seasons while addition of stop logs partially or fully blocks drainage, holding water in the fields during periods when drainage is not needed or during periods of drought. Controlled drainage has also been shown to reduce the amount of nitrates leaving the field and moderate the volume of water entering nearby streams, thereby improving water quality and aquatic habitats.
In 2016, water control structures were installed at the drain outlets on two adjacent 100-acre fields located in the headwaters of Stokes River. Although water control structures have been installed in both fields, one will remain open throughout the year to allow full drainage while the other will be actively managed throughout the season. The controlled structure will be opened pre-harvest season and during storm events when field drainage is required and closed during the growing season to maintain good soil moisture conditions and after harvest when higher water tables will not affect crops.
The following methods will be used to assess the effectiveness of controlled drainage:
- water samples will be collected at each drain outlet every four days throughout the season using an automated water sampler and after significant storm events using grab samples to compare phosphorus, nitrate and sediment concentrations coming off the fields
flow meters will be installed at each drain outlet to compare the volume of water coming off the fields
crop yields will be measured after harvest to compare impacts of controlled and traditional drainage on productivity
soil moisture will be visually assessed from crop conditions (e.g., wilting), and soil samples will be collected to assess soil organic matter