Hydrology and groundwater nutrient concentrations in a ditch-drained agroecosystem
Hydrology and groundwater nutrient concentrations in a ditch-drained agroecosystem
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沟渠农业生态系统中的水文和地下水养分浓度
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
A. Allen
中科院分区：
文献类型：
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作者：
P. Vadas;M. Srinivasan;P. Kleinman;J. Schmidt;A. Allen
摘要：在切萨皮克湾流域，从沟渠排水，耕地地下水氮（N）和磷（P）的传输还没有得到充分的调查。我们监测了27个月的水文和地下水的N和P浓度在26浅（~ 3米[10英尺]）威尔斯在严重沟，家禽谷物农场马里兰州9下东海岸。地下水位在浅沟上方和下方波动，但总是高于深沟。因此，地下水流向浅沟是间歇性的，但流向深沟是连续的。地下水位随着降雨迅速上升，但在降雨后的第一天又从15厘米（6英寸）下降到60厘米（24英寸）。此后，地下水位下降速度迅速下降。地下水位经常位于底土粘土层的顶部。虽然栖息持续只有24至48小时，养分运输可以加速，如果快速，横向运动的水沟渠发生。地下水中NO3-N浓度大于10 mg L−1的现象频繁且普遍存在，表明该农场可能存在地下氮流失。地下水中溶解态磷含量较高，但磷在地下水中的迁移受到限制。雨水渗透通过表土动员土壤P进入地下水和移动相当高浓度的P深1.5米（4英尺），其中P浓度升高持续数天或数周。地下水磷浓度最大的高水位水文相结合的最大土壤磷浓度。输送到浅沟的地下水磷显然是由近沟土壤磷条件控制，而输送到深沟的P是由深层地下水如何流动。因此，限制土壤磷积累在近沟区可能有助于减少磷输送到浅沟，并增加通过低磷底土的地下水流路径的长度可能有助于减少磷输送到深沟。
Abstract: Groundwater nitrogen (N) and phosphorus (P) transport from ditch-drained, cultivated fields has not been adequately investigated in the Chesapeake Bay watershed. We monitored hydrology and groundwater N and P concentrations in 26 shallow (~ 3 m [10 ft]) wells for 27 months on a heavily ditched, poultry-grain farm on Maryland9s Lower Eastern Shore. Water tables fluctuated above and below shallow ditches, but were always higher than deep ditches. Thus, groundwater flow to shallow ditches was intermittent, but flow to deep ditches was continuous. Water tables rose rapidly with rain, but drained back from 15 to 60 cm (6 to 24 in) the first day after rain. The rate of water table fall decreased rapidly thereafter. Water tables frequently perched on top of subsoil clay horizons. Although perching persisted only 24 to 48 hours, nutrient transport could be accelerated if rapid, lateral movement of water to ditches occurs. Frequent and widespread concentrations of groundwater NO3-N greater than 10 mg L−1 show subsurface N loss from the farm is probable. High concentrations of dissolved P existed in groundwater, but P movement in groundwater was restricted. Rain infiltrating through topsoils mobilized soil P into groundwater and moved considerably high concentrations of P as deep as 1.5 m (4 ft), where elevated P concentrations persisted for days or weeks. Groundwater P concentrations were greatest where high water table hydrology combined with the greatest soil P concentrations. Delivery of groundwater P to shallow ditches was apparently controlled by near-ditch soil P conditions, while P delivery to deep ditches was controlled by how deep groundwater flowed. Therefore, limiting soil P accumulation in near-ditch zones may help reduce P delivery to shallow ditches, and increasing the length of groundwater flow paths through low-P subsoils may help reduce P delivery to deep ditches.