这项工作是由一个能力建设补助金颁发给马里兰州东海岸大学（UMES）由粮食和农业研究所资助了一部分。作者希望在建立降雨模拟器和开展降雨模拟感谢唐 - 马汉（UMES）对他的帮助。亦感谢给珍妮丝多诺霍（UMES）的实验室进行分析和本科生学生（UMES）为他们开展的降雨模拟试验样品和加工的帮助。

1。土壤的收集和准备<ol><li>从土壤剖面，以准确地表示在土壤表面的物理和化学条件的表面地平线收集的土壤。注意：如果可能的土壤应该从顶部5厘米表面被收集。用于收集土壤的面积应足够小，以限制不同土壤的物理和化学性质。 </li><li>通过粗（20毫米）筛筛的土壤以除去岩石。注：筛分是比较容易，如果土壤是有点湿润。 </li><li>传播过筛土壤载于一薄层的重篷布以促进干燥，优选在温室或温暖的室内环境。 </li><li>混合土用铲子，耙子或拉从一个侧面篷布其他的边缘，犹如折叠的巨型卡尔佐。注意：小心不要撕裂或撕裂用铲子或耙边缘的篷布。重复此过程数次，直到土壤充分混合。 </li><li>取10个样品从在桩充分混合土的不同的地方，并进行Mehlich-3磷测试17测试同质性。注意：同质时达到的10个样品的结果有变化系数的&lt;0.05（CV）。其中：CV =标准差/平均值。 </li><li>如果Mehlich-3磷试验的CV值&gt; 0.05，继续土壤混合，重复同质性检验。 </li></ol> 2。包装盒土<ol><li>注：土箱应均匀体积的长度的相同的尺寸，宽度和深度（100厘米×20厘米×7.5厘米）与9 5毫米的排水孔在底部。箱应具有5厘米唇和在一端有一个收集槽（ 图1）。 </li><li>行的盒与4层奶酪布的底部，以保持土壤从洗出孔中的框中，同时允许水通过时的土壤饱和。 </li><li>受够舀干，过筛，均质包的第一个土箱欲使土入禁区的时候理顺（约3.5公分），以填补它的一半左右深。传播的土壤均匀，配有一台砖包装。注：土壤应足够干燥，从而不会砖的压力下紧凑。 </li><li>添加另外2厘米厚的土，并拉平用匀轨距到5厘米，即泄漏到沟槽（ 图2）的框的唇缘的高度的填充深度。 </li><li>权衡土被添加到第一填充框的金额，以及土壤的相同的重量加至所有其余的框。把每框实现为5厘米和均匀的堆积密度的土壤深度。 </li><li>真空土箱的排水沟，以删除在包装过程溅入水沟任何土壤。 </li></ol> 3。安装土箱中的降雨模拟器<ol><li>定位构造出2 x 6英寸的降雨模拟器的中心压力处理的木材框架赖以土箱瓦特生病放置。注意：帧应该有一个横向构件在中间，以提供刚性。在一个无底框放置土盒最小化，将立即从土箱下面一个坚实的平台，否则会发生飞溅，并允许自由排水从在箱子底部的孔。 </li><li>水泥块框的位置的高度，允许收集瓶放置和漏斗下面就以安装在平台上土箱子前面的排水沟收集的嘴。 </li><li>进一步提高了平台的背面，用砖，木材和垫片，使得土壤框放置在平台上的背面比所述箱的前高3厘米，导致3％的坡度。通过将一个电路板（&gt; 100厘米长）在土箱的背面安装在平台上测量斜率。使用一个木匠的水平，保持板级，提高了平台的背部，使包装盒正面为3厘米以下的水平板（ 图3 </strong&gt;的）。注：请务必将平台的正面和背面是从侧面平到另一边。 </li><li>定位的开销喷嘴正下方的点，并避免放置一个盒在该位置，以避免大滴从喷嘴落下的土壤框降雨事件的开始或结束时，然后将5或6箱均匀间隔的平台上。标记的盒子的位置，始终把箱子在这些相同的位置上。 </li></ol> 4。选择灌溉水的来源<ol><li>选择一个灌溉水源，是相对自由的所有元素和化合物，特别是那些感兴趣的研究。提前研究，以确定水的纯度的分析水源。注意：如果需要，交换树脂应该被用来实现所希望的水的纯度。 </li><li>提供一个主要水源到模拟降雨超过8磅的压力和5加仑的流速。注：正常市源超过这些最低要求目。如果使用的水箱和水泵，确保泵有能力提供供水超过最小压力和流量。 </li></ol> 5。选择喷嘴尺寸使用<ol><li>选择了用于模拟降雨四个标准喷嘴尺寸之一。注意：每个喷嘴具有最佳性能的压力和流量，以达到合适的液滴尺寸和强度（ 表1）。选择喷嘴尺寸在一个特定的研究中使用的是相对于被代表的自然降水事件的强度（厘米/小时）来确定。 </li></ol> 6。模拟降雨机的操作<ol><li>定位（1）单杆球阀（ 图4）至关闭位置，杠杆在全管90度角，并开启主水源（市政或泵）。 </li><li>打开的（3）压力调节阀（ 图4）反时针方向对r顶部的正方形固定螺钉唤起的压力和完全打开下一序位线（4）线的流量控制阀。 </li><li>打开（1）单杆球阀（ 图4），并完全通过旋转螺丝顺时针实现靠近降雨模拟器的顶部（6）压力表约8磅调整（3）压力调节阀。注意：一旦（3）压力调节阀已被设置为稍微超过所需的喷嘴压力下，它不应该有降雨模拟器除非主要水源的压力变化的操作过程中进行调整。 </li><li>部分关闭（4）在线流量控制阀（ 图4），直到（5）流量计读取使用的流量大约在每分钟加仑的喷嘴和（6）压力表读数为近似磅喷嘴在使用中（ 表1）。 </li><li>关闭（1）单杆球阀（ 图4）停止流动，而不改变流速和压力设定。 </li></ol> 7。喷嘴校准和降雨均匀度<ol><li>覆盖在5或6的空箱子土用胶带底部的孔，以防止水泄漏出来的箱子，把它们摆放在木架上的标记位置（见步骤3.4）。 </li><li>位置并保持的2英寸PVC管的10英尺长有45°弯头连接到端部到喷嘴并打开（1）单杆球阀。 </li><li>从PVC管收集排出的大量筒为10秒。 </li><li>作轻微的调整到（4）中在线流量控制阀，并重复10秒的集合，直到10秒的流量相匹配的喷嘴在使用中（ 见表1）对应的值。一旦正确的流率实现的，使用该值在流量计中的流量监测变化的手段，由于可能的压力波动。注意：对于正确校准喷头，日E-10秒的流量是一个更准确的测量比对流量计的读数。 </li><li>除去PVC管的10英尺长，以允许雨水浸湿框区域，并注意降雨开始的时间。 </li><li>经过整整10分钟通过定位10英尺的PVC管在喷嘴分流流量和关闭（1）单杆球阀突然停止降雨。 </li><li>测量水倾入量筒收集在每个盒子的体积（ml），并计算降雨深度除以体积的盒子的底部（2,000 平方厘米）的区域。 </li><li>计算变异降雨量系数。注：降雨均匀性是实现当降雨量在5或6盒有变化&lt;0.05的系数。其中：CV =标准差/平均值。 </li><li>如果CV为不小于0.05时，转动喷嘴¼转更紧，并重复校准过程。注意：该喷嘴可能需要被翻数倍达到小于0.05简历。 </li><li>一旦低于0.05简历实现，重复校准几次，以确保整个运行的降雨强度是一致的。 </li></ol> 8。进行模拟降雨<ol><li>校准后，将包装盒土在木框架上的显着位置（见步骤3.4）。 </li><li>位置径流收集瓶和下面的漏嘴漏斗，防止雨水直接落入阴沟里用回形针附上盾在阴沟里（ 图5）。 </li><li>重复步骤7.2-7.5重新调整喷嘴流量紧接一个模拟降雨事件，并开始降雨。 </li><li>记录径流开始时对于每个盒子时排水从排水喷管转离缓慢滴的连续流。 </li><li>事件通过切换收集瓶期间或在收集径流样品在规定的时间间隔预定持续时间的事件的结束。 </li><li>要终止降雨事件，通过将10英尺的PVC管在喷嘴突然转移流动和关闭（1）单杆球阀停止降雨。 </li><li>使用量筒或质量假设水重1克/厘米2收集径流样品和记录集。 </li><li>充分混合样本，使所有沉积物悬浮状态，然后采取一个子样本进行化验分析。 </li></ol>

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作者宣称没有竞争的财务权益。

径流主要由两种机制，渗产流和饱和多余的径流18产生的，是由土壤性质，前期土壤水分，地形和降雨强度的影响。降雨模拟可以用来固定降雨强度变量和研究为剩余或多个变量。降雨强度和持续时间也可以通过改变喷嘴的大小控制在一个有限的范围内进行研究。为我们进行包装的箱子土壤降雨模拟研究中最关键的步骤是：1）确保土壤盒统一包装; 2）控制前期土壤含水量; 3）校准流量为选定的喷嘴，使墨滴大小和速度接近自然降雨; 4）调整喷嘴位置，以确保在所有土壤箱子均匀的降雨。 在校准过程结束时，小于0.05一次CV被实现为在所有土壤降雨均匀箱，10分钟校准应重复几次，以确保在运行的降雨强度是一致的。简历也可用于计算在运行过程中的一致性。如果对简历在运行过程中均匀度要小于对所有箱子降雨均匀性，考虑将单个运行中重复治疗，以最大限度地降低治疗的变化。否则，以减少与盒位置相关联的错误并在运行时，这两个随机化处理和复制按空格位置，采取措施限制放置在一个位置处理不止一次。 使用这种降雨模拟器的设计和标准协议，用于正确校准模拟器将改善业绩跨越由不同的研究人员进行的研究比较。来自这样的数据可以被用来预测下自然降雨发生了什么以及更好地理解的过程和用于控制从没有损失到环境中的因素污染物nPoint个来源。这样的研究可以产生有价值的数据在发展模型用于自然降雨条件下预测沉积物和化学污染物的径流中的命运和运输。

农业对环境的影响是一个全球性的和迅速增长的关注，尤其是在全球变化的不确定性。降雨是从农业土壤通过地表径流地表水体环境污染物的输送动力。庞大的身躯的研究主要集中于更好地理解降雨和土壤条件之间的相互作用，因为它们决定泥沙，营养和农业土壤农药损失的非点源。本研究的目的是表征前期土壤含水量对表面的命运和运输商业应用尿素，氮（N）肥一个共同的形式，下面发生在施肥后应用24小时的降雨事件的影响。 有尿素在土壤中的命运和运输的研究很少，因为尿素是继施肥和日迅速水解为铵erefore不是经常为运输提供。然而，最近的分水岭研究表明，尿素可以从农业土壤运到沿海水域和事业移向产生有害的毒素1,2有机体群落。实验室和现场试验表明，当软骨藻酸生产硅藻拟菱形藻芦苇（P. australi次）生长于富含尿素海水，软骨藻酸的生成量高于上硝酸盐或铵富集生长时海水3。本研究采用模拟降雨，调查，控制在径流以下商业施肥尿素氮损失的可能性的过程。 由于自然降水的变化，降雨模拟器已经被用于应用统一的降雨率在陆地表面或包装盒的土壤在受控条件下进行评估径流。降雨模拟器最初用来研究土壤糜烂4。然而，多年来他们一直用来衡量其他成分 ​​在土壤中5-7地表径流和渗滤液。利用天然降雨领域的研究也已进行了评估土壤成分的径流损失。自然降水和降水模拟数据之间的趋势遵循类似的模式，指着进程的一致性。因此降雨模拟可用于研究，以预测在自然降雨8发生的事情可能发生。 各种降雨模拟器已经开发，而且通常他们使用的喷嘴的喷雾器在所需的速率和持续时间申请水。就规模而言，降雨模拟器的范围从简单，体积小，携带入渗与直径降雨区9 6到复杂的肯塔基州的降雨模拟器，它涵盖了剧情14.75英尺X 72英尺（4.5米×22男性）10。在研究人体的一个缺点是EMPloyed模拟降雨的是，没有一个统一的标准化设计或协议进行模拟降雨11。事实上，在2011年的“国际降雨模拟器研讨会”在特里尔大学，德国，来自11个参赛国家的科学家的协作社区的结论是降雨模拟和仿真的标准化是必要的，以确保结果的可比性，并进一步促进技术的发展，以克服物理限制和约束12。本研究旨在通过提供一个标准化的协议的详细描述进行模拟降雨使用已被广泛采用在北美使用模拟器来部分解决这一需求。 这个实验是一个更大的研究旨在评估在切萨皮克湾，其中有毒赤潮被称为每年发生的河口水域尿素的来源的一部分。具体的项目个数<html> E中的实验是确定的前期土壤含水量对尿素的径流损失的影响。重复均匀填土箱子被预湿到一个代表50六种不同的水分含量，60，70，80，90，和田间持水量的100％。尿素是表面在150公斤/公顷的速度适用于颗粒状。在24小时的箱子被进行均匀降雨40分钟的时间在3.17厘米/小时，相当于通常发生在切萨皮克湾在马里兰州的东海岸每年一个自然降水事件的速度。径流收集样品以2分钟的间隔，立即用玻璃滤器（0.45μm）过滤，并储存在4℃下，直到被内收集的24小时进行分析。尿素氮浓度，流动注射分析比色法测定13。使用SAS v.9.1 14的数据进行了分析，统计结果被认为是在P点显著≤0.05。 e_content“&gt;是利用在这项研究中，该便携式降雨模拟器满足，是由全国磷16项目开发的设计规范15和协议，在美国和加拿大，这个模拟器的设计和协议已经被广泛采纳为标准方法在决定使用溶解和颗粒态磷流失径流。虽然径流样品的尿素分析，而不是磷，该方法采用统一和一致的降雨土壤包装盒是一样的这是在全国磷简要介绍项目模拟降雨协议。

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			<td height="42" style="height:42px;width:249px;">Rainfall Simulator</td>
			<td style="width:175px;">&#160;Joern&#39;s Inc.</td>
			<td style="width:147px;">TLALOC 3000</td>
			<td style="width:239px;">Size 1.5m x 2.0m (size optional)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:249px;">Rainfall Simulator</td>
			<td>&#160;Joern&#39;s Inc.</td>
			<td style="width:147px;">TLALOC 4000</td>
			<td>Size 2.0m x 2.0m (size optional)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Rainfall Nozzle</td>
			<td style="width:175px;">Spraying Systems Inc.</td>
			<td style="width:147px;">3/8HH-SS17WSQ</td>
			<td>Size 17 nozzle</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Rainfall Nozzle</td>
			<td style="width:175px;">Spraying Systems Inc.</td>
			<td style="width:147px;">3/8HH-SS24WSQ</td>
			<td>Size 24 nozzle</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Rainfall Nozzle</td>
			<td style="width:175px;">Spraying Systems Inc.</td>
			<td style="width:147px;">1/2HH-SS30WSQ</td>
			<td>Size 30 nozzle</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Rainfall Nozzle</td>
			<td style="width:175px;">Spraying Systems Inc.</td>
			<td style="width:147px;">3/8HH-SS50WSQ</td>
			<td>Size 50 nozzle</td>
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a protocol for conducting rainfall simulation to study soil runoff

降雨是从农业土壤通过地表径流地表水体环境污染物的输送动力。本研究的目的是表征前期土壤含水量对表面的命运和运输商业应用尿素，氮（N）肥一个共同的形式，下面发生在施肥后应用24小时的降雨事件的影响。虽然尿素被认为很容易被水解为铵，因此不经常使用的交通工具，最近的研究表明，尿素可以从农业土壤运到沿海水域的地方被牵连的有害藻华。降雨模拟器用于应用统一的跨降雨已被预湿，以不同的土壤含水量土壤包装盒的符合率。通过控制降雨和土壤的物理特性，前期土壤水分对尿素亏损的影响分别为ISOLA特德。湿润的土壤表现出更短的时间从开始的降雨径流启动，径流更大的总体积，更高的尿素浓度径流，和尿素的径流更大的质量负荷。这些结果还证明在控制了在设计用于分离其它变量，如土壤的物理或化学特性，坡度，土壤覆盖，管理，或降雨特性研究前期土壤水分含量的重要性。由于降雨模拟器的设计，提供类似规模和速度作为自然降雨的雨滴，在一个标准化的协议进行的研究可以产生，反过来，可以用来开发模型预测径流中污染物的命运和运输有价值的数据。

其中一个原因进行目前的实验是探讨可能已经​​从以前的实验，其中正在跨越化肥和畜禽粪便含有尿素几种形式相比，径流损失尿素效果差贡献因素。所有的治疗都应用到了饱和，并允许排放到田间持水量的土壤。业绩尿素造粒治疗五次重复从1-12 mg / L的尿素氮的径流浓度范围。在受控条件下重复之间变化幅度的这个顺序是不能接受的，混淆了实验的结果。径流的总体积和尿素氮浓度在径流之间有很强的关系表明，物理条件，如填料或由于不同的排水和干燥条件变量先行湿气的条件下，分别为致病因素。 为了调查原因在乌尔这种极端变化EA浓度的径流，在目前的实验中所有的箱子都经过精心包装与均匀混合的粉砂壤土中所描绘的图1和图2，尽量减少变化的物理条件相等的权重。实现50，60，70，80，90，和100％作为润湿，然后烘箱烘干少量过筛土壤的测定近似的场能力，以湿润土壤到相应14的前期土壤含水量所需的水的重量，17，19，22，25，和27％计算，加入到箱子，并使其平衡的O / N。降雨模拟遵循上面描述和图3-5所示的确切的协议。 17 WSQ全喷3/8 HH喷嘴（ 表1）是用于输送3.2厘米/小时的降雨强度在40分钟内即相当于通常发生在每年的基础上，东海岸的自然降水事件切萨皮克湾在马里兰州。 <p级=“jove_content”&gt;将所得的总径流体积，载荷和流加权浓度总结于表2中 。有总径流量和前期土壤湿润条件（ 图6）之间有显著的正相关关系。潮湿的土壤有能力少蓄水和造成更大的径流量较低的渗透速率。有时间的径流和前期土壤湿润状况的显著负相关关系（ 图7）。水渗入的时间较长土壤干他们成为湿表面附近之前，造成径流发生。毫不奇怪，有总负荷尿素氮之间的径流量和总径流量（ 图8）的正相关关系。众所周知，在流量通常是总负荷的一个强有力的预测水文研究。如何浓度的行为响应于径流事件是难以预料。流加权concentratioN的计算和总结了荷载为每2分钟径流收集和总径流量划分。它相当于在40分钟内降雨期间结束时在单个集合径流的浓度。在这项研究中，有一个在径流和前期土壤湿润条件（ 图9）一个显著正流加权浓度之间的关系。鉴于径流量和前期土壤含水量之间的正线性关系和流量加权浓度和前期土壤湿润条件下，总负荷尿素氮，预计前期土壤湿润条件之间存在显著的正相关关系。然而，这显著关系最好由一个指数方程（ 图10）中所述。 为了形象化尿素氮损失径流随着时间的推移，个人2分钟的浓度和累积负荷在土箱分别代表前期土壤湿润康迪特的一个复制离子作图在40分钟内降雨时间间隔（ 图11）。虽然浓度在径流会有所变化无规律随时间（ 例如，在水分90％的情况下），浓度一般先从高，随着时间而减少。累计负荷随着时间的推移也更为平滑函数，它们说明了前面讨论的显著关系。时间径流较长，尿素氮浓度径流较低，和累积负荷较少的干燥土壤。虽然尿素在土壤中迅速水解，当降雨发生表面应用的时间内，多了N仍然存在于尿素的形式和受径流损失。尿素是一种中性分子和不强烈吸附到土壤颗粒的表面。由于水的降雨事件的早期阶段渗入土壤干它承载溶解尿素分解成土壤，远离地表径流区。当径流不会开始，有较少的尿素公关ESENT和浓度径流较低。从实际意义上来说，尿素几乎总是被干燥的条件下应用的农场设备无法穿越的土壤是在田间持水量。 <img alt="图1" fo:content-width="5in" fo:src="/files/ftp_upload/51664/51664fig1highres.jpg" src="/files/ftp_upload/51664/51664fig1.jpg" /> 图1。填充土壤径流盒示意图。金属盒（100厘米×20厘米×7.5厘米）与前端5cm的唇是挤满了土壤5厘米深。径流溢出5cm的唇被收集在屏蔽对降雨直接掉进排水沟连接的排水沟。九个直径5毫米的孔允许水渗入土壤的框排出，防止积水。附排水沟底部的前边缘附近的乳头使径流水排入漏斗和收集瓶positioned乳头下方。 <img alt="图2" fo:content-width="5in" fo:src="/files/ftp_upload/51664/51664fig2highres.jpg" src="/files/ftp_upload/51664/51664fig2.jpg" /> 图2。盒包装材料。在盒子的底部约4层纱布防止土壤流失，但允许水自由排出。流平仪由丙烯酸玻璃两个木制板之间夹着的是一样宽的箱（20厘米），深（2.5厘米）的箱壁之间的差值（7.5厘米）和排水沟的顶部（5厘米）。由静止板包装盒上的唇丙烯酸玻璃用于土壤年级的排水沟的深度。 <img alt="图3" fo:content-width="5in" fo:src="/files/ftp_upload/51664/51664fig3highres.jpg" src="/files/ftp_upload/51664/51664fig3.jpg" /> 图3。宝sitioning平台。定位平台，使得当包装盒的土壤是在适当位置，它们都具有相同的斜率。在这项研究中，所期望的坡度为3％。同时举行了板级，定位平台，让下坡，箱子阴沟年底为3厘米以下的上坡结束。该平台应该是在横坡方向的水平。 <img alt="图4" fo:content-width="5in" fo:src="/files/ftp_upload/51664/51664fig4highres.jpg" src="/files/ftp_upload/51664/51664fig4.jpg" /> 图4。降雨模拟器控制从水源开始，并通过管道系统对喷嘴进展 （1）单杆球阀：这是一个快速切断阀。杆与管道是;杆在跨越管90度角是关闭的。使用此阀，以打开和关闭流动，而不会干扰控制压力阀和流量。完全打开和完全关闭。 ðØ不要尝试使用该阀来控制流量。 （2）沉淀过滤：定期检查过滤器并根据需要，防止泥沙堵塞更换滤芯。 （3）压力调节阀：该阀控制从这个角度提出在管路中的压力。压力太大可能会破坏管道，软管或接头。 （4）在线路的流量控制阀（闸阀）：该阀被用于微调，以达到所需的流速和喷嘴压力流至喷嘴。 （5）流量计：测量近似流量。 （6）压力表：测量在喷嘴近似压力。 <img alt="图5" fo:content-width="5in" fo:src="/files/ftp_upload/51664/51664fig5highres.jpg" src="/files/ftp_upload/51664/51664fig5.jpg" /> 图5。盒子定位于模拟降雨的平台上放置 5或6盒为每个模拟降雨事件标记位置。避免放置一箱直接在喷嘴下，防止直接滴到一个盒子表面。 <img alt="图6" fo:content-width="5in" fo:src="/files/ftp_upload/51664/51664fig6highres.jpg" src="/files/ftp_upload/51664/51664fig6.jpg" /> 图6。总径流量是积极与前期土壤含水量 （R 2 = 0.64） 相关 。 <img alt="图7" fo:content-width="5in" fo:src="/files/ftp_upload/51664/51664fig7highres.jpg" src="/files/ftp_upload/51664/51664fig7.jpg" /> 图7。时间径流负前期土壤含水量 （R 2 = 0.48） 相关 。湿土壤表面很快饱和。降雨量超过了饱和土的渗透系数产生径流。 <img alt="图8"<html> FO：内容宽度=“5英寸”FO：SRC =“/ files/ftp_upload/51664/51664fig8highres.jpg”SRC =“/ files/ftp_upload/51664/51664fig8.jpg”/&gt; 图8。总负荷尿素氮是积极与径流总量 （R 2 = 0.81） 相关 。在径流量差异压倒在尿素氮的径流浓度的差异。 <img alt="图9" fo:content-width="5in" fo:src="/files/ftp_upload/51664/51664fig9highres.jpg" src="/files/ftp_upload/51664/51664fig9.jpg" /> 图9。的尿素氮流加权浓度是积极与前期土壤含水量 （R 2 = 0.66） 相关 。干燥土壤浸润允许该浸出尿素氮进入土壤并远离土壤表面。当径流确实发生，少尿素氮可在表面移动的径流。 5英寸“FO：SRC =”/ files/ftp_upload/51664/51664fig10highres.jpg“SRC =”/ files/ftp_upload/51664/51664fig10.jpg“/&gt; 图10。总负荷尿素氮是积极与前期土壤含水量 （R 2 = 0.74） 相关 。总径流量和前期土壤含水量之间和尿素氮流量加权浓度和前期含水量之间的积极关系结合起来，导致指数关系（Y = 0.2043ë0.0405x）。 <img alt="图11" fo:content-width="5in" fo:src="/files/ftp_upload/51664/51664fig11highres.jpg" src="/files/ftp_upload/51664/51664fig11.jpg" /> 图11。尿素氮浓度随着时间的推移每个前期土壤水分conten吨一个复制累计负荷的关系 。虽然尿素氮浓度并不总是顺利通过功能时，显著关系以前<html> LY讨论可以可视化。 <table border="0" cellpadding="0" cellspacing="0" width="613"><colgroup><col /><col /><col /><col /><col /></colgroup><tbody><tr height="29"><td height="29" style="height:29px;width:173px;">喷嘴尺寸</td><td style="width:96px;">强度</td><td style="width:145px;">最佳压力</td><td style="width:83px;">流</td><td style="width:117px;"> 10秒的流速</td></tr><tr height="29"><td height="29" style="height:29px;width:173px;"></td><td style="width:96px;">厘米/小时</td><td style="width:145px;"> PSI </td><td style="width:83px;"> GPM </td><td style="width:117px;">毫升</td></tr><tr height="29"><td height="29" style="height:29px;width:173px;"> 17 WSQ全喷3/8 HH </td><td style="width:96px;"> 3.2 </td><td style="width:145px;"> 6 </td><td style="width:83px;"> 1.5 </td><td style="width:117px;"> 940 </td></tr><tr height="29">：173px;“&gt; 24 WSQ全喷3/8 HH </td><td style="width:96px;"> 3.3 </td><td style="width:145px;"> 6 </td><td style="width:83px;"> 1.8 </td><td style="width:117px;"> 1,140 </td></tr><tr height="29"><td height="29" style="height:29px;width:173px;"> 30瓦特全喷1/2 HH </td><td style="width:96px;"> 6 </td><td style="width:145px;"> 5.0 </td><td style="width:83px;"> 2.2 </td><td style="width:117px;"> 1,250 </td></tr><tr height="29"><td height="29" style="height:29px;width:173px;"> 50瓦特全喷1/2 HH </td><td style="width:96px;"> 7 </td><td style="width:145px;"> 4.1 </td><td style="width:83px;"> 3.7 </td><td style="width:117px;"> 2,300 </td></tr></tbody></table> 表1中。已确定与此降雨模拟器及其相关的降雨强度，压力和流量等参数的使用喷嘴尺寸图。喷嘴尺寸呈现。选择喷嘴尺寸取决于所需的降雨强度。降雨强度和持续时间对应于一个指定位置的研究有一定的回报周期沉淀的事件。喷嘴尺寸17 WSQ被用于这项研究。 40分钟降雨持续时间在3.2厘米/小时的强度等同于通常发生在切萨皮克湾在马里兰州的东海岸每年一个自然降水事件。 <table border="0" cellpadding="0" cellspacing="0" width="513"><colgroup><col /><col span="2" /><col /></colgroup><tbody><tr height="26"><td height="26" style="height:27px;width:128px;">土壤水分</td><td style="width:129px;">总决选</td><td style="width:129px;">流加权</td><td style="width:127px;">总负荷</td></tr><tr height="26"><td height="26" style="height:27px;width:128px;"> ％ </td><td style="width:129px;">容积（L） </td><td style="width:129px;">浓度</td><td style="width:127px;"> （毫克尿素<html> -N） </td></tr><tr height="26"><td height="26" style="height:27px;width:128px;"></td><td style="width:129px;"></td><td style="width:129px;"> （毫克L-1尿素氮） </td><td style="width:127px;"></td></tr><tr height="26"><td height="26" style="height:27px;width:128px;"> 27† </td><td style="width:129px;"> 2.96 </td><td style="width:129px;"> 4.99 </td><td style="width:127px;"> 13.66 </td></tr><tr height="26"><td height="26" style="height:27px;width:128px;"> 27 </td><td style="width:129px;"> 2.87 </td><td style="width:129px;"> 4.37 </td><td style="width:127px;"> 12.55 </td></tr><tr height="26"><td height="26" style="height:27px;width:128px;"> 25 </td><td style="width:129px;"> 2.52 </td><td style="width:129px;"> 3.57 </td><td style="width:127px;"> 8.62 </td></tr><tr height="26"><td height="26" style="height:27px;width:128px;"> 25 </td><td style="width:129px;"> 1.81 </td><html> PX;“&gt; 2.33 </td><td style="width:127px;"> 4.21 </td></tr><tr height="26"><td height="26" style="height:27px;width:128px;"> 22 </td><td style="width:129px;"> 2.52 </td><td style="width:129px;"> 2.18 </td><td style="width:127px;"> 5.50 </td></tr><tr height="26"><td height="26" style="height:27px;width:128px;"> 22 </td><td style="width:129px;"> 2.47 </td><td style="width:129px;"> 1.54 </td><td style="width:127px;"> 3.81 </td></tr><tr height="26"><td height="26" style="height:27px;width:128px;"> 19 </td><td style="width:129px;"> 1.99 </td><td style="width:129px;"> 1.72 </td><td style="width:127px;"> 3.41 </td></tr><tr height="26"><td height="26" style="height:27px;width:128px;"> 19 </td><td style="width:129px;"> 2.35 </td><td style="width:129px;"> 3.70 </td><td style="width:127px;"> 8.68 </td></tr><tr height="26"><td height="26" style="height:27px;width:128px;"> 17 </td><td style="width:129px;"> 1.91 </td>H：129px;“&gt; 1.69 </td><td style="width:127px;"> 3.22 </td></tr><tr height="26"><td height="26" style="height:27px;width:128px;"> 17 </td><td style="width:129px;"> 1.66 </td><td style="width:129px;"> 0.90 </td><td style="width:127px;"> 1.50 </td></tr><tr height="26"><td height="26" style="height:27px;width:128px;"> 14 </td><td style="width:129px;"> 1.51 </td><td style="width:129px;"> 0.78 </td><td style="width:127px;"> 1.18 </td></tr><tr height="26"><td></td><td></td><td></td><td height="26" style="height:27px;"> †重复的数字代表两个重复为每个水分含量</td></tr></tbody></table> 表2。前期土壤含水量，总径流量，流量加权尿素氮浓度和总尿素氮负荷模拟降雨之后。重复的数字代表两个重复为每个水分含量

Watch this Scientific Journal Video about A Protocol for Conducting Rainfall Simulation to Study Soil Runoff at JoVE.com

A Protocol for Conducting Rainfall Simulation to Study Soil Runoff

降雨模拟器用来申请均匀降雨土壤包装盒中的尿素，一个非点源污染环境的命运和运输的研究一致的速度。在均匀土壤和降雨条件下，前期土壤含水量施加了强大的控制权丧失的尿素地表径流。

一个协议，用于开展降雨模拟研究土壤径流

Rainfall is a driving force for the transport of environmental contaminants from agricultural soils to surficial water bodies via surface runoff. The ...

a-protocol-for-conducting-rainfall-simulation-to-study-soil-runoff

Research

JoVE Journal

Environment

20.6K 次观看.  University of Maryland Eastern Shore. 降雨模拟器用来申请均匀降雨土壤包装盒中的尿素，一个非点源污染环境的命运和运输的研究一致的速度。在均匀土壤和降雨条件下，前期土壤含水量施加了强大的控制权丧失的尿素地表径流。 

视频: A Protocol for Conducting Rainfall Simulation to Study Soil Runoff

Design and Operation of a Continuous 13C and 15N Labeling Chamber for Uniform or Differential, Metabolic and Structural, Plant Isotope Labeling

Tracing rare stable isotopes from plant material through the ecosystem provides the most sensitive information about ecosystem processes; from CO2 fluxes and soil organic matter formation to small-scale stable-isotope biomarker probing. Coupling multiple stable isotopes such as 13C with 15N, 18O or&#160;2H has the potential to reveal even more information about complex stoichiometric relationships during biogeochemical transformations. Isotope labeled plant material has been used in various studies of litter decomposition and soil organic matter formation1-4. From these and other studies, however, it has become apparent that structural components of plant material behave differently than metabolic components (i.e. leachable low molecular weight compounds) in terms of microbial utilization and long-term carbon storage5-7. The ability to study structural and metabolic components separately provides a powerful new tool for advancing the forefront of ecosystem biogeochemical studies. Here we describe a method for producing 13C and 15N labeled plant material that is either uniformly labeled throughout the plant or differentially labeled in structural and metabolic plant components.
Here, we present the construction and operation of a continuous 13C and 15N labeling chamber that can be modified to meet various research needs. Uniformly labeled plant material is produced by continuous labeling from seedling to harvest, while differential labeling is achieved by removing the growing plants from the chamber weeks prior to harvest. Representative results from growing Andropogon gerardii Kaw demonstrate the system&#39;s ability to efficiently label plant material at the targeted levels. Through this method we have produced plant material with a 4.4 atom%13C and 6.7 atom%15N uniform plant label, or material that is differentially labeled by up to 1.29 atom%13C and 0.56 atom%15N in its metabolic and structural components (hot water extractable and hot water residual components, respectively). Challenges lie in maintaining proper temperature, humidity, CO2 concentration,&#160;and light levels in an airtight 13C-CO2 atmosphere for successful plant production. This chamber description represents a useful research tool to effectively produce uniformly or differentially multi-isotope labeled plant material for use in experiments on ecosystem biogeochemical cycling.

Design and Operation of a Continuous 13C and 15N Labeling Chamber for Uniform or Differential, Metabolic and Structural, Plant Isotope Labeling

This method explains how to build and operate a continuous 13C and 15N isotope labeling chamber for uniform or differential plant tissue labeling. Representative results from metabolic and structural labeling of Andropogon gerardii are discussed.

设计一个连续和操作<sup&gt; 13</sup&gt; C和<sup&gt; 15</sup&gt;Ñ贴标商会统一或差分，代谢和结构，植物同位素标记

Tracing rare stable isotopes from plant material through the ecosystem provides the most sensitive information about ecosystem processes; from CO2 fluxes ...

科研

环境科学

Design and Construction of an Urban Runoff Research Facility

As the urban population increases, so does the area of irrigated urban landscape. Summer water use in urban areas can be 2-3x winter base line water use due to increased demand for landscape irrigation. Improper irrigation practices and large rainfall events can result in runoff from urban landscapes which has potential to carry nutrients and sediments into local streams and lakes where they may contribute to eutrophication. A 1,000 m2 facility was constructed which consists of 24 individual 33.6 m2 field plots, each equipped for measuring total runoff volumes with time and collection of runoff subsamples at selected intervals for quantification of chemical constituents in the runoff water from simulated urban landscapes. Runoff volumes from the first and second trials had coefficient of variability (CV) values of 38.2 and 28.7%, respectively. CV values for runoff pH, EC, and Na concentration for both trials were all under 10%. Concentrations of DOC, TDN, DON, PO4-P, K+, Mg2+, and Ca2+ had CV values less than 50% in both trials. Overall, the results of testing performed after sod installation at the facility indicated good uniformity between plots for runoff volumes and chemical constituents. The large plot size is sufficient to include much of the natural variability and therefore provides better simulation of urban landscape ecosystems.

This paper describes the design, construction, and function of a 1,000 m2 facility containing 24 individual 33.6 m2 field plots equipped for measuring total runoff volumes with time and collection of runoff subsamples at selected intervals for quantification of chemical constituents in the runoff water from simulated home lawns.

设计一个城市径流研究设施的建设

As the urban population increases, so does the area of irrigated urban landscape. Summer water use in urban areas can be 2-3x winter base line water use ...

Experimental Protocol for Manipulating Plant-induced Soil Heterogeneity

Coexistence theory has often treated environmental heterogeneity as being independent of the community composition; however biotic feedbacks such as plant-soil feedbacks (PSF) have large effects on plant performance, and create environmental heterogeneity that depends on the community composition. Understanding the importance of PSF for plant community assembly necessitates understanding of the role of heterogeneity in PSF, in addition to mean PSF effects. Here, we describe a protocol for manipulating plant-induced soil heterogeneity. Two example experiments are presented: (1) a field experiment with a 6-patch grid of soils to measure plant population responses and (2) a greenhouse experiment with 2-patch soils to measure individual plant responses. Soils can be collected from the zone of root influence (soils from the rhizosphere and directly adjacent to the rhizosphere) of plants in the field from conspecific and heterospecific plant species. Replicate collections are used to avoid pseudoreplicating soil samples. These soils are then placed into separate patches for heterogeneous treatments or mixed for a homogenized treatment. Care should be taken to ensure that heterogeneous and homogenized treatments experience the same degree of soil disturbance. Plants can then be placed in these soil treatments to determine the effect of plant-induced soil heterogeneity on plant performance. We demonstrate that plant-induced heterogeneity results in different outcomes than predicted by traditional coexistence models, perhaps because of the dynamic nature of these feedbacks. Theory that incorporates environmental heterogeneity influenced by the assembling community and additional empirical work is needed to determine when heterogeneity intrinsic to the assembling community will result in different assembly outcomes compared with heterogeneity extrinsic to the community composition.

Understanding the role of environmental heterogeneity in species coexistence has typically focused on types of heterogeneity that are extrinsic to the community&#8217;s species composition. We provide novel detailed methods for creating soil heterogeneity treatments using soils subject to plant-soil feedback conditioning, or heterogeneity intrinsic to the community composition.

用于操纵植物诱导土壤异质性的实验协议

Coexistence theory has often treated environmental heterogeneity as being independent of the community composition; however biotic feedbacks such as ...

Soil Sampling and Isolation of Entomopathogenic Nematodes (Steinernematidae, Heterorhabditidae)

Entomopathogenic nematodes (a.k.a. EPN) represent a group of soil-inhabiting nematodes that parasitize a wide range of insects. These nematodes belong to two families: Steinernematidae and Heterorhabditidae. Until now, more than 70 species have been described in the Steinernematidae and there are about 20 species in the Heterorhabditidae. The nematodes have a mutualistic partnership with Enterobacteriaceae bacteria and together they act as a potent insecticidal complex that kills a wide range of insect species.
Herein, we focus on the most common techniques considered for collecting EPN from soil. The second part of this presentation focuses on the insect-baiting technique, a widely used approach for the isolation of EPN from soil samples, and the modified White trap technique which is used for the recovery of these nematodes from infected insects. These methods and techniques are key steps for the successful establishment of EPN cultures in the laboratory and also form the basis for other bioassays that consider these nematodes as model organisms for research in other biological disciplines. The techniques shown in this presentation correspond to those performed and/or designed by members of S. P. Stock laboratory as well as those described by various authors.

Soil Sampling and Isolation of Entomopathogenic Nematodes Steinernematidae, Heterorhabditidae

Entomopathogenic nematodes are soil-inhabiting roundworms that parasitize a wide range of insects. We demonstrate sampling methods used for the isolation of these nematodes from the soil using two techniques: the insect baiting and the modified White trap, for the recovery of nematodes from soil samples and infected insect cadavers, respectively.

土壤采样及昆虫病原线虫的分离（Steine​​rnematidae，异小）

Entomopathogenic nematodes (a.k.a. EPN) represent a group of soil-inhabiting nematodes that parasitize a wide range of insects. These nematodes belong to ...

A Protocol for Collecting and Constructing Soil Core Lysimeters

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).

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.

一种用于收集和构建土芯协议测渗计

Leaching of nutrients from land applied fertilizers and manure used in agriculture can lead to accelerated eutrophication of surface water. Because the ...

Soil Lysimeter Excavation for Coupled Hydrological, Geochemical, and Microbiological Investigations

Studying co-evolution of hydrological and biogeochemical processes in the subsurface of natural landscapes can enhance the understanding of coupled Earth-system processes. Such knowledge is imperative in improving predictions of hydro-biogeochemical cycles, especially under climate change scenarios. We present an experimental method, designed to capture sub-surface heterogeneity of an initially homogeneous soil system. This method is based on destructive sampling of a soil lysimeter designed to simulate a small-scale hillslope. A weighing lysimeter of one cubic meter capacity was divided into sections (voxels) and was excavated layer-by-layer, with sub samples being collected from each voxel. The excavation procedure was aimed at detecting the incipient heterogeneity of the system by focusing on the spatial assessment of hydrological, geochemical, and microbiological properties of the soil. Representative results of a few physicochemical variables tested show the development of heterogeneity. Additional work to test interactions between hydrological, geochemical, and microbiological signatures is planned to interpret the observed patterns. Our study also demonstrates the possibility of carrying out similar excavations in order to observe and quantify different aspects of soil-development under varying environmental conditions and scale.

This study presents an excavation method for investigating subsurface hydrological, geochemical, and microbiological heterogeneity of a soil lysimeter. The lysimeter simulates an artificial hillslope which was initially under homogeneous condition and had been subjected to approximately 5,000 mm of water over eight cycles of irrigation in an 18-month period.

土壤蒸渗仪开挖加之水文，地球化学和微生物调查

Studying co-evolution of hydrological and biogeochemical processes in the subsurface of natural landscapes can enhance the understanding of coupled ...

A Gusseted Thermogradient Table to Control Soil Temperatures for Evaluating Plant Growth and Monitoring Soil Processes

Thermogradient tables were first developed in the 1950s primarily to test seed germination over a range of temperatures simultaneously without using a series of incubators. A temperature gradient is passively established across the surface of the table between the heated and cooled ends and is lost quickly at distances above the surface. Since temperature is only controlled on the table surface, experiments are restricted to shallow containers, such as Petri dishes, placed on the table. Welding continuous aluminum vertical strips or gussets perpendicular to the surface of a table enables temperature control in depth via convective heat flow. Soil in the channels between gussets was maintained across a gradient of temperatures allowing a greater diversity of experimentation. The gusseted design was evaluated by germinating oat, lettuce, tomato, and melon seeds. Soil temperatures were monitored using individual, battery-powered dataloggers positioned across the table. LED lights installed in the lids or along the sides of the gradient table create a controlled temperature chamber where seedlings can be grown over a range of temperatures. The gusseted design enabled accurate determination of optimum temperatures for fastest germination rate and the highest percentage germination for each species. Germination information from gradient table experiments can help predict seed germination and seedling growth under the adverse soil conditions often encountered during field crop production. Temperature effects on seed germination, seedling growth, and soil ecology can be tested under controlled conditions in a laboratory using a gusseted thermogradient table.

Traditional thermogradient tables create a range of temperatures across the surface. Welding gussets perpendicular to the surface of a thermogradient table will control temperature in depth increasing possible research applications.

一个插角Thermogradient表来控制土壤温度为评估植物生长和监测土壤过程

Thermogradient tables were first developed in the 1950s primarily to test seed germination over a range of temperatures simultaneously without using a ...

Measuring and Mapping Patterns of Soil Erosion and Deposition Related to Soil Carbonate Concentrations Under Agricultural Management

Spatial patterns of soil erosion and deposition can be inferred from differences in ground elevation mapped at appropriate time increments. Such changes in elevation are related to changes in near-surface soil carbonate (CaCO3) profiles. The objective is to describe a simple conceptual model and detailed protocol for repeatable field and laboratory measurements of these quantities. Here, accurate elevation is measured using a ground-based differential global positioning system (GPS); other data acquisition methods could be applied to the same basic method. Soil samples are collected from prescribed depth intervals and analyzed in the lab using an efficient and precise modified pressure-calcimeter method for quantitative analysis of inorganic carbon concentration. Standard statistical methods are applied to point data, and representative results show significant correlations between changes in soil surface layer CaCO3 and changes in elevation consistent with the conceptual model; CaCO3 generally decreased in depositional areas and increased in erosional areas. Maps are derived from point measurements of elevation and soil CaCO3 to aid analyses. A map of erosional and depositional patterns at the study site, a rain-fed winter wheat field cropped in alternating wheat-fallow strips, shows the interacting effects of water and wind erosion affected by management and topography. Alternative sampling methods and depth intervals are discussed and recommended for future work relating soil erosion and deposition to soil CaCO3.

Spatial patterns of soil erosion and deposition can be inferred from differences in ground elevation mapped at appropriate time increments. Such changes in elevation are related to changes in near-surface soil carbonates. Repeatable methods for field and laboratory measurements of these quantities and data analysis methods are described here.

农业经营条件下土壤侵蚀和沉积与土壤碳酸盐浓度关系的测量与制图

Spatial patterns of soil erosion and deposition can be inferred from differences in ground elevation mapped at appropriate time increments. Such changes ...

Use of Principal Components for Scaling Up Topographic Models to Map Soil Redistribution and Soil Organic Carbon

Landscape topography is a critical factor affecting soil formation and plays an important role in determining soil properties on the earth surface, as it regulates the gravity-driven soil movement induced by runoff and tillage activities. The recent application of Light Detection and Ranging (LiDAR) data holds promise for generating high spatial resolution topographic metrics that can be used to investigate soil property variability. In this study, fifteen topographic metrics derived from LiDAR data were used to investigate topographic impacts on redistribution of soil and spatial distribution of soil organic carbon (SOC). Specifically, we explored the use of topographic principal components (TPCs) for characterizing topography metrics and stepwise principal component regression (SPCR) to develop topography-based soil erosion and SOC models at site and watershed scales. Performance of SPCR models was evaluated against stepwise ordinary least square regression (SOLSR) models. Results showed that SPCR models outperformed SOLSR models in predicting soil redistribution rates and SOC density at different spatial scales. Use of TPCs removes potential collinearity between individual input variables, and dimensionality reduction by principal component analysis (PCA) diminishes the risk of overfitting the prediction models. This study proposes a new approach for modeling soil redistribution across various spatial scales. For one application, access to private lands is often limited, and the need to extrapolate findings from representative study sites to larger settings that include private lands can be important.

Landscape processes are critical components of soil formation and play important roles in determining soil properties and spatial structure in landscapes. We propose a new approach using stepwise principal component regression to predict soil redistribution and soil organic carbon across various spatial scales.

利用主成分扩展地形模型绘制土壤再分配和土壤有机碳

Landscape topography is a critical factor affecting soil formation and plays an important role in determining soil properties on the earth surface, as it ...

Microplot Design and Plant and Soil Sample Preparation for 15Nitrogen Analysis

Many&#160;nitrogen fertilizer studies evaluate the overall effect of a treatment on end-of-season measurements such as grain yield or cumulative N losses. A stable isotope approach is necessary to follow and quantify the fate of fertilizer derived N (FDN) through the soil-crop system. The purpose of this paper is to describe a small-plot research&#160;design utilizing non-confined 15N enriched microplots for multiple soil and plant sampling events over two growing seasons and provide sample collection, handling, and processing protocols for total 15N analysis. The methods were demonstrated using a replicated study from south-central Minnesota planted to corn (Zea mays L.). Each treatment consisted of six corn rows (76 cm row-spacing) 15.2 m long with a microplot (2.4 m by 3.8 m) embedded at one end. Fertilizer-grade urea was applied at 135 kg N&#8729;ha-1 at planting, while the microplot received urea enriched to 5 atom % 15N. Soil and plant samples were taken several times throughout the growing season, taking care to minimize cross-contamination by using separate tools and physically separating unenriched and enriched samples during all procedures. Soil and plant samples were dried, ground to pass through a 2 mm screen, and then ground to a flour-like consistency using a roller jar mill. Tracer studies require additional planning, sample processing time and manual labor, and incur higher costs for 15N enriched materials and sample analysis than traditional N studies. However, using the mass balance approach, tracer studies with multiple in-season sampling events allow the researcher to estimate FDN distribution through the soil-crop system and estimate unaccounted-for FDN from the system.

Microplot Design and Plant and Soil Sample Preparation for 15Nitrogen Analysis

A microplot design for 15N tracer research is described to accommodate multiple in-season plant and soil sampling events. Soil and plant sample collection and processing procedures, including grinding and weighing protocols, for 15N analysis are put forth.

微图设计及植物和土壤样品制备，进行15次氮气分析

Many&#160;nitrogen fertilizer studies evaluate the overall effect of a treatment on end-of-season measurements such as grain yield or cumulative N losses. ...