J Environ Qual. 2019 Jul;48(4):869-879. doi: 10.2134/jeq2018.12.0440.
Reducing eutrophication in surface water is a major environmental challenge in many countries around the world. In cold Canadian prairie agricultural regions, part of the eutrophication challenge arises during spring snowmelt when a significant portion of the total annual nutrient export occurs, and plant residues can act as a nutrient source instead of a sink. Although the total mass of nutrients released from various crop residues has been studied before, little research has been conducted to capture fine-timescale temporal dynamics of nutrient leaching from plant residues, and the processes have not been represented in water quality models. In this study, we measured the dynamics of P and N release from a cold-hardy perennial plant species, alfalfa ( L.), to meltwater after freeze-thaw through a controlled snowmelt experiment. Various winter conditions were simulated by exposing alfalfa residues to different numbers of freeze-thaw cycles (FTCs) of uniform magnitude prior to snowmelt. The monitored P and N dynamics showed that most nutrients were released during the initial stages of snowmelt (first 5 h) and that the magnitude of nutrient release was affected by the number of FTCs. A threshold of five FTCs was identified for a greater nutrient release, with plant residue contributing between 0.29 (NO) and 9 (PO) times more nutrients than snow. The monitored temporal dynamics of nutrient release were used to develop the first process-based predictive model controlled by three potentially measurable parameters that can be integrated into catchment water quality models to improve nutrient transport simulations during snowmelt.
减少地表水中的富营养化是世界上许多国家面临的主要环境挑战。在加拿大寒冷的草原农业区，富营养化的部分挑战出现在春季融雪期间，此时全年养分出口的很大一部分发生，而植物残体可以作为养分源而不是汇。尽管以前已经研究了各种作物残体释放的养分总量，但很少有研究用于捕获植物残体中养分淋溶的精细时间尺度动态，并且这些过程在水质模型中没有得到体现。在这项研究中，我们通过受控融雪实验测量了耐寒多年生植物紫花苜蓿（ L.）在融雪后对融雪水的 P 和 N 释放动力学。通过在融雪前使紫花苜蓿残体经历不同数量的大小均匀的冻融循环（FTC）来模拟各种冬季条件。监测到的 P 和 N 动态表明，大多数养分在融雪的初始阶段（前 5 小时）释放，养分释放的幅度受 FTC 数量的影响。确定了 5 个 FTC 的阈值以实现更大的养分释放，植物残体贡献的养分比雪多 0.29（NO）到 9（PO）倍。监测到的养分释放时间动态用于开发第一个基于过程的预测模型，该模型由三个潜在可测量的参数控制，可以集成到集水区水质模型中，以改善融雪期间的养分输送模拟。
