Effect of management practices on hydrology and nutrient losses from a tile-drained field under freeze-thaw conditions

统计表明，每年约有3.8千兆克的磷（P）被输出到魁北克南部的圣劳伦斯河。这导致在省水质标准（0.03毫克L-1）的容许负荷的P超过68%的监测站。最近的研究表明，地下瓦片排水农田是这些地区水质退化的主要原因。在加拿大东部，这些养分损失主要发生在12月至5月的非生长季节。尽管大孔隙和土壤纳米颗粒促进的磷迁移是瓦排水区磷流失的关键机制，但很少有研究调查冻融条件下的水文过程和磷流失。 另一方面，管理措施可用于减少非生长季节的养分流失。覆盖作物和减少耕作是瓷砖排水农田的主要选择;然而，并非所有潜在的做法都是有用的，事实上，没有发现增加溶解磷从农田输出。这种现象可能是由于免耕田中存在较多的大孔隙所致。然而，尚未开展任何研究，以关注这一问题或将这些管理做法与地下水管理战略相结合。 因此，这项实地研究的目标是制定最佳的管理措施，以减轻在融雪和融雪后时期的磷流失，并了解冬季水文和微孔纳米颗粒促进磷流失瓷砖排水的影响。实验将在魁北克的24个地下排水场进行，采用完全随机区组设计，因子为2 x 2 x 2。这三个因素是地下水位管理、种植制度和耕作。对于每个因素，将有2个水平：控制排水与自由排水，有和没有冬季覆盖作物的玉米-大豆轮作，以及串联圆盘+田间耕耘机与免耕。因此，将有8个处理，每个处理将分配3个地块。天气，瓷砖排水，地表径流，降雪，积雪，土壤冰和液态水含量，雪升华，土壤大孔隙度和纳米颗粒，以及水中所有形式的P将被集中测量，特别是在融雪和融雪后时期。在加拿大创新基金会的赞助下，最近购买了一台NanoBrook Zetasizer、一台测雪仪和一台雪包分析仪（SPA），以促进这种测量（价值247 208美元）。

Statistics have shown that about 3.8 Gg of phosphorus (P) per year was exported to the St. Lawrence River in southern Quebec. This resulted in tolerable loads of P under provincial water quality standards (0.03 mg L-1) being exceeded at 68% of monitoring stations. Recent studies have shown that subsurface tile-drained cropland was the major contributor to water quality degradation in those regions. In eastern Canada these nutrient losses occurred mainly during the non-growing season of December to May. Notwithstanding the fact that macropore and soil nanoparticle-facilitated phosphorus transport are the key mechanisms of P losses from tile-drained regions, very few study have been conducted to investigate the hydrological processes and P losses under freeze-thaw conditions. On the other hand, management practices can be applied to mitigate nutrient losses during the non-growing season. Cover crops and reduced tillage are the primary options used on tile-drained fields; however, not all potential practices are useful, indeed, no till was found to increase dissolved phosphorus export from fields. This phenomenon might be attributed to there being more macropores in no-till fields. However, no study has been developed to focus on this question or combining those management practices with water table management strategies. Therefore, the objectives of this field study are to develop best management practices to mitigate P losses during the snowmelt and post-snowmelt periods and to understand the effect of winter hydrology and microporosity on nano-particle facilitated P loss in tile drainage. The experiment will be conducted at a 24-plot subsurface drainage site in Quebec with a complete randomized block design with a 2 x 2 x 2 factorial. The three factors are water table management, cropping system, and tillage. For each factor, there will be 2 levels: controlled drainage vs. free drainage, corn-soybean rotation with and without winter cover crop, and tandem disk + field cultivator versus no-till. Therefore, there will be 8 treatments and 3 plots will be assigned to each treatment. Weather, tile drainage, surface runoff, snowfall, snowpack, soil ice and liquid water content, snow sublimation, soil macroporosity and nano-particles, and all forms of P in water will be intensively measure, in particular during snowmelt and post-snowmelt period. Sponsored by the Canadian Foundation of Innovation, a NanoBrook Zetasizer, a scintillometer, and a Snow Pack Analyzer (SPA) were recently purchased to facilitate such measurements (value $247,208).