一种用于收集和构建土芯协议测渗计
Summary
A detailed method for extraction and assembly of intact soil core lysimeters and their use for study of leachate and associated loss of nutrients from surface applied poultry litter is demonstrated.
Abstract
Leaching of nutrients from land applied fertilizers and manure used in agriculture can lead to accelerated eutrophication of surface water. Because the landscape has complex and varied soil morphology, an accompanying disparity in flow paths for leachate through the soil macropore and matrix structure is present. The rate of flow through these paths is further affected by antecedent soil moisture. Lysimeters are used to quantify flow rate, volume of water and concentration of nutrients leaching downward through soils. While many lysimeter designs exist, accurately determining the volume of water and mass balance of nutrients is best accomplished with bounded lysimeters that leave the natural soil structure intact.
Here we present a detailed method for the extraction and construction of soil core lysimeters equipped with soil moisture sensors at 5 cm and 25 cm depths. Lysimeters from four different Coastal Plain soils (Bojac, Evesboro, Quindocqua and Sassafras) were collected on the Delmarva Peninsula and moved to an indoor climate controlled facility. Soils were irrigated once weekly with the equivalent of 2 cm of rainfall to draw down soil nitrate-N concentrations. At the end of the draw down period, poultry litter was applied (162 kg TN ha-1) and leaching was resumed for an additional five weeks. Total recovery of applied irrigation water varied from 71% to 85%. Nitrate-N concentration varied over the course of the study from an average of 27.1 mg L-1 before litter application to 40.3 mg L-1 following litter application. While greatest flux of nutrients was measured in soils dominated by coarse sand (Sassafras) the greatest immediate flux occurred from the finest textured soil with pronounced macropore development (Quindocqua).
Introduction
Delmarva半岛接壤切萨皮克湾的东岸，是家美国最大的家禽生产区之一。大约6亿只鸡，估计有75万吨的粪便是从生产每年1这些鸟的产生。大部分的肥料是局部用作农田肥料的修正案。由于有机肥的历史高位速率，养分如氮和磷的积累在土壤中，现在可以通过地下浸出2易受异地损失。大部分的地下水流是指向一个广泛的沟渠，最终排放到切萨皮克湾3的网络。抬到湾的营养素都与在海湾的健康状况的下降，由于水体富营养化4。
营养物质的异地损失连接养分管理需要专门的工具来监控水文流动和相关营养物质传输。测渗计代表用于表征并通过土壤量化营养素的运动器械的主要类别。测渗计在监测营养物质流的使用历史悠久，在渗漏水5-7，从可进行调整，以应对土壤基质潜能，使张力测渗计他们更好的估计植物可利用水分，零张力测渗计是比较有代表性的过程在自由排水的发生。所有方法lysimetery目前固有的偏见。例如，有些渗漏池太小，在自然土壤中充分体现空间的复杂过程，或者是过于庞大和昂贵提供异构土壤8的良好的统计复制。此外，泛渗仪需要在他们之上的土壤趋于饱和，收集渗滤液和效率不高相比，在测量矩阵流紧张9渗漏池。
封闭蒸渗仪系统，诸如零张力土壤芯测渗计（也称为土壤整料测渗计），大大提高了与水的预算和相关的污染物的预算（ 例如 ，营养的预算）进行了10的信心。这些渗漏池是最有代表性的，当它们含有土壤的完整核;充满了重新包装的土壤渗漏池并不认为，影响溶质和颗粒化合物都11,12运输的原有结构，视野，大孔连接。从实验的立场来看，有利于的原状土条件更高的复制的方法是有利的，因为存在于土壤的物理和化学性质13的固有空间变异。
两种优选的方法已被用于收集完好土壤芯测渗计：落锤和切削头。前者已被更普遍进行的，因为它可以与作为雪橇火腿作为简单的设备来实现聚（小渗漏池）。当适当地进行，土壤核心集合与落锤已被证明是相对成本效益，尤其是在与其他核化技术相比。但是，通过驱动一个蒸渗仪外壳到地面施加的剪切力会导致拖尾和板结，生产蒸渗仪内是不能代表乡土的条件，甚至可能有利于某些类型的水的运动（ 例如 ，旁路流量，或沿流土壤中的核心优势）。其结果是，一些研究人员已经优选切去一个完整的土壤与钻井设备或其它挖掘设备5的使用取样器的。
各种材料已被用作肠衣土壤芯测渗计。钢管和盒是成本比较低，耐用，易于获得且可用于收集较大的测渗计由于其强度14-17。然而，尽管钢是用于评价相对的浸出令人满意硝酸这样atively不反应的化合物，在钢中的铁与磷酸反应，因此必须进行包衣或磷浸出的研究以其它方式处理。通常，塑料外壳用于研究磷浸出，如厚壁（表80）的PVC管，可以承受一个落锤（如果使用的话）的影响，并保持它的结构时，获得较大直径土壤芯（ 例如 ，≥30厘米）18-22。
一般情况下，土芯渗仪进行了分析易地 。一旦收集，土壤芯测渗计可以安装在户外“蒸渗农场”，其中周围的土壤和地上气候代表自然场的条件。例如，在瑞典，瑞典农业大学一直保持着三个独立的蒸渗仪农场在过去的三十年中，分析可扩展到直径30厘米INTA农药的命运和运输，长期土壤肥力试验管理规范克拉芯23。土芯渗漏池也受到室内浸出试验那里是气候条件24,25更大的控制权。刘等人使用降雨模拟器定期灌溉抓数组作物26下土核心渗漏池。基贝特和昆都采用手工灌溉技术，通过土柱27,28研究砷和养分流失。
各种土壤和水文过程可以从土芯渗仪推断。坤等人 （2015）使用的直径30厘米的PVC柱渗漏池进行调查后施用尿素氮28浸出。通过收集在下面的灌溉事件不同的时间间隔渗滤液，他们能够迅速，逐渐流区分，前者假定由大孔隙流为主，后者假定为基质流为主。由于尿素很容易接触无线水解时日土，他们解释渗滤液升高浓度的尿素施肥后为绕过土壤基质大孔迁移的证据收集不久的存在。随着时间的推移，他们发现高浓度的浸出液中的不同形式的氮，跟踪应用尿素转化为铵初期水解后，再铵转化与硝化硝酸盐。
为了说明在设计，实施和解释土芯蒸渗仪实验的考虑，我们进行了在美国的中大西洋沿岸平原发现了四个不同的土壤调查。该研究测量的浸出浓度与前和干燥家禽粪便（ 即家禽“垃圾”）28的申请后，硝酸盐流失。从家禽垫料的应用，土壤养分损失的切萨皮克湾的健康关键问题，并了解所应用的互动需要家禽粪便和农业土壤理化性质，提高养分管理建议。我们在座提取完整土芯渗漏池，跟踪土壤水分，并解释从这些土壤硝态氮淋差损失的详细方法。
这个实验是进行从Delmarva半岛，美国的27,28农田土壤评估养分流失一个更大的研究的一部分。在2010年这里，我们提出这些研究结果未发表土芯测渗计是从在美国特拉华州，马里兰州和弗吉尼亚州的地点采集。尽管最初的实验是从论文土壤磷评估浸出，浸出硝酸盐也监测。
从切萨皮克湾流域的大西洋沿岸平原四种常见的农田土壤进行了采样：Bojac（粗壤质，混合，半主动，热能Typic Hapludult）; Evesboro（梅西奇，涂层LamellIC Quartzipsamment）; Quindocqua（细壤土，混合，活跃，梅西奇Typic Endoaquult）;檫（细壤质，硅质，半主动，梅西奇Typic Hapludult）。对于每一个土壤，地平线形态从由列（ 表1）的挖掘露出的剖面说明。土壤的表面纹理从砂（Evesboro），以壤质细沙/砂壤土范围（Bojac檫）以粉质壤土（Quindocqua）。虽然所有土壤曾与家禽废弃物历来受精，没有已在之前的研究中10个月的应用。所有的土壤已经在免耕玉米产量为土芯蒸渗仪采集前至少一个赛季。
收集后，土芯渗漏池被运送到州立学院，PA的美国农业部simulatorium设施。在那里，他们都受到室内灌溉实验（22-26℃），以评估与家禽垫料的应用养分流失。特别，渗漏池用2厘米周水灌溉，持续8周，直到硝酸盐渗滤液被土壤之间的平衡。家禽废弃物（干家禽粪肥），然后在162千克公顷全氮灌溉-1下继续进行5个星期的速率施加到所有土壤的表面上。每隔5分钟连续记录湿度传感器体积含水量，整个灌溉和浸出周期。渗滤液后24小时收集一次第7天前立即灌溉。
用简单的描述性统计数据来说明差异之前和之后的垃圾应用程序之间的土壤浸出液中的数量和质量上的差异，以及从土壤核心渗漏池渗滤液数据进行了分析。因为土壤湿度传感器被安置在仅复制土壤芯渗仪的两个用于每个土壤（Evesboro，Bojac，檫，Quindocqua），土壤水分含量的统计是根据N = 2，而小号渗沥液深度tatistics，硝态氮含量和硝态氮通量从10土壤核心渗漏池为Evesboro，Bojac檫和5 Quindocqua土芯渗漏池的。评估的复制的土壤中的重要性，进行了计算不同的复制数的变化（CV）为渗滤液深度的系数。蒙特卡洛模拟方法被用来重复地品尝来自各土壤组内重复总数土芯渗仪（N = 3）的一个子集（10 Evesboro，Bojac，檫; 5为Quindocqua）。
Protocol
Representative Results
Discussion
蒸渗仪收集的重要步骤
浸出研究阐明了土壤理化性质和粪便管理对氮素损失浅层地下水的影响。土壤的物理性质，如土壤质地，团粒结构和堆积密度介导的水和溶质的渗透。准确地确定渗滤液量和溶质浓度取决于由以下关键步骤蒸渗收集期间保持这些土壤的物理性质的完整性：1）的蒸渗和落锤而列被驱动到土壤必须保持水平; 2）蒸渗仪内的土壤必须检查压实; 3）土柱的底部?…
Disclosures
The authors have nothing to disclose.
Acknowledgements
The authors are grateful to the staff of USDA-ARS Pasture Systems and Watershed Management Unit. David Otto was important to both the design and construction of the custom made drop hammer (aka ‘The Intimidator’). Michael Reiner and Terry Troutman assisted in the collection and construction of the lysimeters reported in this study. Sarah Fishel, Charles Montgomery and Paul Spock performed all of the nutrient analyses reported in this manuscript.
Materials
| Schedule 80 PVC Pipe | Fry's Plastic | Call | Sold in 10 ft lengths |
| Fernco Fittings | Fry's Plastic | Call | 12 in. diameter |
| Type II PVC plates for perforated discs | AIN Plastic | Call | Sold in 4' x 8' sheets of PVC II Vintec II |
| Schedule 40 PVC Caps | Fry's Plastic | Call | 12 in. diameter |
| Stainless Steel Screws | Fastenal | 135716 | #8 Bugle Head Phillips Drive Sharp Point Grade 18-8 Stainless Steel |
| Silicone II Caulk | Lowe's | 447488 | |
| Nylon Tube Fitting | United State's Plastic Corp. | 61137 | 0.5 in. NPT |
| Foodgrade Tubing | Lowe's | 443209 | 0.5 in. vinyl |
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