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

统计数据显示，每年约有3.8克的磷(P)被出口到魁北克南部的圣劳伦斯河。这导致68%的监测站超过了省级水质标准（0.03 mg L-1）的磷容许负荷。最近的研究表明，地下排水的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月的非生长期。尽管大孔和土壤纳米颗粒促进的磷运输是旱涝地区磷流失的关键机制，但很少有研究对冻融条件下的水文过程和磷流失进行研究。******另一方面，可以采用管理措施来减轻非生长季节的营养损失。覆盖作物和减少耕作是旱作农田的主要选择；然而，并不是所有可能的做法都是有用的，事实上，没有发现任何耕作增加了农田的溶解磷出口。这种现象可能与免耕田的大孔隙较多有关。但是，没有研究集中于这个问题或将这些管理做法与地下水位管理战略结合起来。******因此，本实地研究的目标是制定最佳管理措施，以减轻融雪期间和融雪后时期的磷损失，并了解冬季水文和微孔隙度对纳米颗粒促进磷流失的影响。实验将在魁北克省的一个24块地下排水场地进行，采用完全随机区设计，具有2 2 2因子。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个级别：控制排水与自由排水，玉米-大豆轮作有和没有冬季覆盖作物，串联圆盘+大田耕作机与免耕。因此，将有8个处理，每个处理将分配3个地块。天气、排水、地表径流、降雪、积雪、土壤冰和液态水含量、雪升华、土壤宏观孔隙和纳米颗粒以及水中所有形式的磷将被集中测量，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，最近购买了一台纳米布鲁克Zetasizer，一台闪烁仪和一台积雪分析仪（SPA）来进行此类测量（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 2 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).**