Changes in groundwater quality and agriculture in forty years on the Twin Falls irrigation tract in southern Idaho
Changes in groundwater quality and agriculture in forty years on the Twin Falls irrigation tract in southern Idaho
复制标题
爱达荷州南部双子瀑布灌溉区四十年来地下水质量和农业的变化
DOI：
10.2489/jswc.73.2.107
复制
发表时间：
2018
影响因子：
3.9
通讯作者：
S. Haye
中科院分区：
文献类型：
--
作者：
R. Lentz;D. L. Carter;S. Haye
了解农业景观对浅层地下水质量的长期影响是改善爱达荷州南部双瀑布灌溉区土壤和水管理的必要条件。在1999年和2002年至2007年期间，我们对20世纪60年代末监测的15个隧道排水沟中的10个进行了重新采样，以确定养分浓度和流出流量如何随时间变化而变化，以响应土地管理或气候的变化。自20世纪60年代末以来，奶牛群的数量增加了8倍，这促使人们转向增加饲料种植，这与杂交品种和产量的改善一起，增加了无机肥料和粪肥的使用。20世纪60年代末至21世纪初，隧道排水流出硝酸盐氮（NO3-N）平均浓度持续增加1.4倍（从3.06 mg L−1 [ppm]增加到5.06 mg L−1 [ppm]），平均氯化物（Cl）减少10%（从49.2 mg L−1 [ppm]减少到44.2 mg L−1 [ppb]），溶解活性磷（DRP）总体减少14%（从14减少到12 μg L−1 [ppb]）。然而，10个隧道中有3个隧道的DRP浓度在此期间呈上升趋势，并且DRP的上升速度与限制动物饲养或住宅开发的入侵增加呈正相关。采样期间隧道流量的减少与隧道排水土地喷灌比例的相应增加呈线性相关（p = 0.01）。然而，进一步从沟灌转变为喷灌不太可能降低隧道排水NO3-N浓度，因为后者与喷灌覆盖的变化无关。在这些土壤中，应更仔细地管理施氮量和时间以及作物吸收或淋溶的有效性，以防止地下水NO3-N浓度继续增加。建议在苜蓿轮作后，配以需氮量大的深根作物，以更好地利用苜蓿死根矿化氮。
Understanding long-term impacts of agricultural landscapes on shallow groundwater quality is needed to improve soil and water management in the Twin Falls irrigation tract in southern Idaho. In 1999 and 2002 through 2007, we resampled 10 of the 15 tunnel drains monitored in a late-1960s study to determine how nutrient concentrations and flow rates of outflows have changed over time in response to changes in land management or climate. Since the late 1960s, an 8-fold increase in the dairy herd has driven shifts toward increased feed cropping, which, along with improved hybrids and production, increased inorganic and manure fertilizer use. The late-1960s to early-2000s period saw a consistent 1.4-fold increase in mean tunnel-drain outflow nitrate-nitrogen (NO3-N) concentrations (from 3.06 to 5.06 mg L−1 [ppm]), a 10% decrease in mean chloride (Cl) (from 49.2 to 44.2 mg L−1 [ppm]), and an overall 14% decrease in dissolved reactive phosphorus (DRP) (14 to 12 μg L−1 [ppb]). However, 3 of the 10 tunnels exhibited increased DRP concentrations during the period, and the rate of DRP increase was positively related to increasing encroachment of confined animal feeding operations or residential development. Decreases in tunnel flow between sampling periods were linearly related to corresponding increases in the fraction of sprinkler irrigation employed on lands drained by the tunnels (p = 0.01). However, further conversion from furrow to sprinkler irrigation is unlikely to reduce tunnel drain NO3-N concentrations since the latter were unrelated to changes in sprinkler coverage. The amount and timing of applied N and availability for crop uptake or leaching should be more carefully managed in these soils to prevent continued increases in groundwater NO3-N concentrations. It is recommended that alfalfa (Medicago sativa L.) rotations be followed by deep-rooted crops with large N requirements to better utilize N mineralized from killed alfalfa roots.