Alkalinity of Irrigation Return Water Influences Nutrient Removal Efficacy of Floating Treatment Wetland Systems1

Water quality concerns often prevent reuse of captured irrigation return water for irrigation of specialty crops. Prior research indicated alkalinity of specialty crop operation irrigation varies from 0 to >500 mg.L−1 ( >0.06 oz.gal−1) CaCO3 across the United States. Floating treatment wetlands (FTWs) are an option for remediation of nutrients in irrigation return water, but effects of variable alkalinity on nutrient removal efficiency of FTWs are unknown. An experimental FTW system was developed to quantify the effect of alkalinity on the growth and nutrient uptake capacity of three plant species. ‘Rising Sun' Japanese iris (Iris ensata ‘Rising Sun’ Thunb.), upright sedge (Carex stricta Lam.);, and switchgrass (Panicum virgatum L.). were grown for 6 weeks at one of five alkalinity treatment levels, representing the alkalinity range of nursery and greenhouse irrigation runoff: 0, 100, 200, 300, and 400 mg.L−1 CaCO3 (0, 0.01, 0.02, 0.04, 0.05 oz.gal−1 CaCO3). Overall, Japanese iris demonstrated consistent remediation across each alkalinity treatment for both nutrient load reduction and plant accumulation. Species of iris warrant greater consideration and use in bioremediation systems. Both upright sedge and switchgrass could be used in systems with appropriate alkalinity levels. Future work should consider assessing novel plants at different points within their growth cycle, extended exposure durations, and decreased hydraulic retention time. Index words: Aquatic plant, nitrogen, phosphorus, sodium bicarbonate, nitrogen speciation. Species Used in this study: ‘Rising Sun' Japanese iris (Iris ensata ‘Rising Sun' Thunb.); upright sedge (tussock sedge) (Carex stricta Lam.); switchgrass (Panicum virgatum L.).

Soil and vegetation characteristics of a peatland near Lake Édouard in Mauricie National Park, Québec, Canada

The majority of plant communities within the peatland near Lake Édouard belongs to the poor fen group. They are containing poor fen species such as <i>Myrica gale</i>, <i>Carex rostrata</i>, <i>Glyceria canadensis</i>, <i>Calamagrostis canadensis</i>, <i>Carex canescens</i>, <i>Carex stricta</i>, <i>Alnus rugosa</i> and <i>Sphagnum subsecundum</i>. Members of these taxa grow in association with a group of marsh species and with <i>Chamaedaphne calyculata</i> and <i>Sphagnum majus</i>, species characteristic of bogs. The soil are of the humisol great group, being well decomposed and relatively rich in nutrient elements but ranging from extremely to strongly acidic. Four new associations are noted: <i>Sphagno-Juncetum brevicaudati</i>, <i>Sphagno-Hypericetum boreale</i>, <i>Sphagno-Glycerietum canadensis</i> and <i>Carici canescenti</i>-<i>Sphagnetum maji</i>. The distribution of vegetation appears dependent on ground relief and, consequently, on the level and quality of water in the peatland.

The biomass and nutrient levels of Calamagrostis canadensis and Carex stricta under different hydrologic and fungicide regimes

We examined whether fungicide and the subsequent reduction of soilborne pathogenic fungi would differentially enhance the productivity and foliar nutrient content of two coexisting species, Calamagrostis canadensis (Michx.) Beauv. and Carex stricta Lam. This was tested under hydrologic regimes that simulated those in prairie wetlands and included a 32-d cycle (flooded 16 d, dry 16 d), 6-d cycle (flooded 3 d, dry 3 d), flooded, well-watered, and dry hydroperiods. Calamagrostis canadensis biomass increased 26%–45% in the wet hydroperiods (6-d cycle, well watered, and flooded) when fungicide was applied but remained fairly constant over all hydroperiods in nonfungicide treatments. Calamagrostis canadensis grown in the wet hydroperiods without fungicide produced the same biomass and growth rates as plants treated with fungicide in the dry hydrologic regime, suggesting that pathogenic fungi in wet hydrologic regimes have the same effect as major environmental stresses such as drought. In contrast, the biomass and growth rate of Carex stricta generally did not vary significantly with fungicide treatment. The only exception was in the rapidly alternating hydroperiod (6-d cycle), where Carex stricta treated with fungicide produced 48% more biomass and grew 46% faster than plants not treated with fungicide. Mean concentrations of foliar phosphorus generally were not significantly different between the fungicide and nonfungicide treatments for either plant species, while foliar nitrogen concentrations were higher in both species when treated with fungicide in the 32-d cycle, dry, and well-watered hydroperiods. The effect of fungicide on the biomass and foliar nutrients of these two co-occurring plant species depended on the species and the hydrologic regime, and our results suggest that seasonal and interannual changes in hydrologic regimes may confer a temporary advantage to one species or the other that, over the long term, allow them to coexist.Key words: benomyl fungicide, foliar nitrogen, foliar phosphorus, hydroperiod, marsh reed grass, wetland.