This research project showed that the installation of water control structures reduced the discharge from the fields, thereby conserving water and reducing nutrient loads in the tile drainage. Higher water table elevation provided water for crop uptake thus reducing crop water stress. From a hydrologic standpoint, drainage occurs mainly in the spring. The discharge occurred only at one of the sites with controlled drainage, while not at the other site with a water control structure, or the control site. Further analysis of the quality of water discharging from the research sites shows high P concentrations over the three years at all study locations.
The water quality results indicate that drainage water management alone is insufficient to reduce N and P concentrations and that further research into other treatment methods is needed. The majority of the total P was inorganic, although most of the organic phosphorus was hydrolyzable thus possibly available to crops or the microbiome. Concentrations of specific organic P classes were quite variable, most likely a result of the complex nutrient cycling of the microbiome. The drainage water samples showed that organic P compounds were not a possible source of eutrophication from these fields. The dataset from this study contributed to numerical modeling of a drainage management strategy that reduces nutrient losses in the Holland Marsh.
The Holland Marsh Growers Association have shown a receptivity to utilizing the results of this project to promote drainage water management. The Lake Simcoe Regional Conservation Authority, together with federal and provincial departments of agriculture can use these results to develop standards for the control of eutrophication in Lake Simcoe. The private sector, specifically designers of drainage systems and manufacturers of water control structures, can now promote this technology for water conservation and drainage water quality management.
