Evaluation of Phosphorus Inputs Into the Lake Simcoe Watershed From Nursery Sod Production.

Eutrophication is the main cause of deterioration of surface water quality.  As was declared in the Lake Simcoe Phosphorus Reduction Strategy, phosphorus (P) is a key water quality concern in Ontario. The intensification of farming in many areas has created imbalances in P inputs into the soil. Occasionally P concentrations in soils build up to levels in excess of agricultural production needs and this excess P escapes from soil and enriches surface runoff and ground waters. The overall goal of our research was to quantify P losses due to runoff from sod production at the field level in the Lake Simcoe watershed. Forty individual plots were constructed to collect water runoff from the sod fields. Six automatic portable water samplers were also installed to collect samples in small waterways situated adjacent to the sod fields. Samples of runoff water were collected every 10 -12 days throughout the year.  Volumes of runoff water from the troughs were measured at each plot. Water samples from autosamplers and troughs were analyzed for total phosphorus and orthophosphates by automated colorimetry techniques. Mean concentration of orthophosphates in water samples collected in all troughs during the spring period for both years of study was significantly lower than in the summer and fall (0.87, 2.33 and 2.86 mg/L for 2010 and 1.49, 2.69 and 2.21 mg/L for 2011, respectively).  Results have shown that brief fluctuations in phosphorus levels in these waters occur right after fertilization. These fluctuations are typically insignificant in streams with a swift current (0.01-0.12 mg/L). In drainage ditches the concentrations are much higher (0.1-3.2 mg/L), but they dissipate as water approaches the Lake. We made an attempt to study phosphorous losses in working farms with real (and very specific) agricultural practices.  At this point, there is no evidence that current management practices for sod production in Ontario are responsible for causing significant phosphorus loading in Lake Simcoe.