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用水平土柱与Green-Ampt模型方法测量土壤入渗性能的原理与误差 总被引：2，自引：0，他引：2
土壤入渗是自然界水循环中的一个重要环节。研究提出了一种新的方法，根据水量／物质平衡原理和水平土柱中土壤剖面含水率分布所遵循的Green—Ampt模型中的活塞假定，测量和计算土壤入渗性能。用天然容重下的风干砂壤土，通过室内水平土柱试验，说明了获取数据的实验方法、过程，并利用提出的数学模型计算得到土壤入渗性能曲线。利用测量得到的土壤入渗性能回归计算得到的入渗水量分别与实际供水量和由土壤含水率的实际分布计算得到的入渗水量进行对比，得到相对误差分别为11．5％、15．89％，而实际供水量与由土壤含水率实际分布计算得到的水量之间的相对误差只有1．02％，说明了该方法的测量精度以及方法精度有进一步提高的可能性。该方法与传统的土壤入渗率测量方法相比，可以测量出土壤初始很高的入渗率，而且试验操作简单，省水，省时，为相关研究提供了有力的工具。 相似文献
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植物叶片的生长与光照度密切相关,尤其在温室大棚内,对光照度的控制要求更高。为同时获取叶片的三维形态与光照分布,该文提出了一种基于双目视觉的纹理植物叶片三维形态与光照度同步测量方法。利用双目视觉原理结合数字图像相关技术,实现叶片三维形态测量;通过植物叶片光照度与图像灰度关系推导,实现三维光照分布测量。该文以网纹草为例,对上述方法进行验证。试验表明:参考子区半径为57 pixels、计算间隔7 pixels时三维形态测量效果最佳;对叶片实施均匀光照,照度仪测量值与图像测量平均值相对误差在6%以内;对叶片实施非均匀光照,测量的光照分布真实反映了叶片光照分布。该方法具有非接触、方便、快捷等优点,为植物叶片的三维形态与光照度测量提供了一种方法,为温室大棚的智能光控提供了数据支撑。 相似文献
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作物叶面积指数和倾角分布函数的一种推算方法 总被引：1，自引：1，他引：1
设计了一种由作物冠层的辐射分布推算作物叶面积指数（ＬＡＩ）和叶倾角分布函数的方法。根据作物冠层中太阳光斑密度与群体结构关系的数学表达式，ＬＡＩ及其在各个叶倾角区间的分布可由不同太阳高度角时冠层内的光斑密度进行估计，而后者可通过观察冠层中的太阳总辐射和散射辐射的分布进行计算。因此，由容易测得的冠层总辐射的透过率，应用与多元回归分析类似的简单方法，就可以估算出难以趋势测量的ＬＡＩ和叶倾角分布函数。用对 相似文献
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作物叶面积指数和叶倾角分布函数的一种推算方法 总被引：2，自引：0，他引：2
设计了一种由作物冠层的辐射分布推算作物叶面积指数（ＬＡＩ）和叶倾角分布函数的方法。根据作物冠层中太阳光斑密度与群体结构关系的数学表达式，ＬＡＩ及其在各个叶倾角区间的分布可由不同太阳高度角时冠层内的光斑密度进行估计，而后者可通过观测冠层中的太阳总辐射和散射辐射的分布进行计算。因此，由容易测得的冠层总辐射的透过率，应用与多元回归分析类似的简单方法，就可以估算出难以直接测量的ＬＡＩ和叶倾角分布函数。用对玉米和油菜进行的实测检验结果表明，推算精度可以满足实际应用的需要。 相似文献
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冬小麦叶面积指数地面测量方法的比较 总被引：12，自引：8，他引：4
该研究以冬小麦为对象,对叶面积指数测量的几种方法（比叶重法、照相法及SUNSCAN测量法）从测量难易程度、误差来源、适宜条件等方面做了比较分析与评价。研究表明比叶重法及照相法在整个生育期间均可使用,而基于SUNSCAN的仪器测量法在冬小麦封垄前的测量还需进一步研究。对SUNSCAN一天内不同时间测量的结果进行了比较,得出最适宜测量时间为13:00－15:00。照相法的测量精度最高,比叶重法次之,SUNSCAN测量需要根据作物生长特点做参数修正。针对SUNSCAN测量LAI提出了一种对叶倾角分布参数进行修正的方法,对3种冬小麦株型品种3个不同生育期进行了参数修正。该研究有助于地面测量叶面积指数的方法选择,同时对提高SUNSCAN测量精度具有参考意义。 相似文献
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水平携带床气固两相流动的实验研究 总被引：1，自引：2，他引：1
为研究氩气和生物质颗粒(玉米秸秆粉末)流在水平携带床热解管中的运动规律，设计了水平携带床透明冷态模拟装置。以油雾粒子为示踪粒子，利用PIV技术(粒子图像测速技术)对氩气流在水平携带床管内的速度分布进行了测量和分析。在氩气流量不变的情况下，对水平携带床管内加入生物质颗粒后的流动速度进行了PIV测量。结果表明，氩气流在到达距离管道入口大于400 mm的区域后已经较为稳定，处于充分发展区；氩气流的速度分布是对称结构，在雷诺数为1695时，其速度分布形状明显不同于层流的抛物线形状，是更加接近于紊流速度分布形状。而相同氩气流量条件下，生物质颗粒速度分布是非对称形状，中心部位生物质颗粒运动速度明显低于气流中心速度；在整个水平携带床内，生物质颗粒都是处于被加速的状态。 相似文献
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土壤电导率的准确、实时和原位获取可为农业生产精准管理提供有效的数据支撑，为提高传统电流-电压四端法测量精度，该研究基于电流-电压四端法3种测量组态，开展土壤电导率主要影响因素（土壤含水率、电极入土深度、土壤坚实度和土壤处理方式）对电流-电压四端法的3种测量组态测量精度影响的试验。结果表明，Wenner和Schlumberger两种测量组态可较好的适用于不同土壤环境条件。进一步以Wenner和Schlumberger两种测量组态所测土壤电导率值为输入量，基于BP神经网络构建了双组态融合的土壤电导率回归模型，并在此基础上设计了一种土壤电导率测量装置，该装置主要包括JESTON nano、STM32单片机数据采集模块、传感器、激励源及差分放大模块等组件。工作稳定性试验结果显示，该装置在不同土壤电导率梯度条件下测量数据的标准偏差均小于0.43 μS/mm，田间性能对比试验结果显示，该装置测量数据的均方根误差值为0.18 μS/mm，测量精度优于传统单独测量组态和市面常用土壤电导率测量仪，以上结果表明所研制的土壤电导率测量装置具有较好的工作稳定性和测量精度。该研究可为田间土壤信息的实时原位采集提供一种高精度的检测工具和技术手段。 相似文献
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土壤水分剖面测量系统设计与应用性能检验 总被引：3，自引：3，他引：0
针对农田环境下观测不同作物根区土壤水分变化的实际需要,研制了一种可快速获取0～200 cm深度范围内土壤剖面含水率的传感器及其测量系统。其中水分传感器工作原理为基于电容边缘场效应测量电极周围介质的介电常数,与土壤接触采用PVC套筒式结构,深度测量为霍尔磁敏传感器阵列,测量系统数据处理平台为PDA。对于测量方法的理论研究,该文给出了传感器工作原理的解析分析,进一步提出了传感器应用性能检验的试验方法。结果表明,该传感器性能指标达到实际应用需求,具备应用推广价值。 相似文献
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基于温度植被干旱指数的江苏淮北地区农业旱情监测 总被引：12，自引：7，他引：5
为实现江苏省淮北地区农业旱情监测,利用Savitzky—Golay(S-G)滤波方法,对2011—2012年江苏省淮北地区1-5月MODIS的归一化植被指数(normalized difference vegetation index,NDVI)和地表温度(land Surface temperature,LST)8 d产品进行重构,去除原8 d数据的噪声,填补受云影响而缺失的数据。基于重建后的NDVI和LST数据,计算温度植被干旱指数(temperature vegetation dryness index,TVDI);分析TVDI和土壤湿度之间的关系,构建土壤湿度反演模型。最后,利用另外1组数据验证所建土壤湿度模型的精度。研究结果表明:1)S-G滤波方法能够提高MODIS LST和NDVI数据质量,并能对缺失数据进行填补;2)TVDI方法能够实现试验区土壤湿度反演,所建模型在试验区具有一定的普适性,反演精度较高(R2=0.575,RMSE=2.59%);3)TVDI方法在江苏省淮北地区干旱监测中得到了较好的应用,能够成功地监测出江苏淮北地区2011年和2012年春旱。该研究可为农业旱情的快速监测提供借鉴。 相似文献
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Tim Mansfeldt 《植物养料与土壤学杂志》2003,166(2):210-219
The long‐term measurement of soil redox potential (EH) by permanently installed Pt electrodes may be restricted by electrode breakdown (electrode rupture and resin leakage) and contamination, especially under wet and strongly reducing soil conditions. The EH of a slightly alkaline (pH 7.1 to 7.3) Calcaric Gleysol developed from marine sediment in the dyked marsh of Schleswig‐Holstein, Northern Germany, was monitored weekly during a 4‐year period using permanently installed Pt electrodes. Measurements were performed in fivefold at 10, 30, 60, 100, and 150 cm. Furthermore, water table level was recorded. Sulfide occurred in 150 cm as a heritage of the previous marine environment. Mean water table level was 84 cm below the soil surface but was characterized by both short‐term and seasonally strong fluctuations. Levels of water table ranged from 33 to >200 cm below soil surface. In consistence with water table level, the EH continually decreased with soil depth. Mean redox conditions were oxidizing at 10 (550 mV) and 30 cm (430 mV), weakly reducing at 60 cm (230 mV), and moderately reducing at 100 (120 mV) and 150 cm depth (–80 mV). Soil hydrology differed markedly during the study as expressed by periods of water saturation for each depth. This was reflected by Pt electrodes response, since period of water saturation and EH were significantly negatively correlated as calculated for each year and depth (rs = –0.971; n = 20; P < 0.01). The 60‐cm depth was most frequently influenced by water table fluctuations, showed the largest EH range (920 mV) and the most distinct seasonal pattern in EH. Good function of the electrodes in this depth can be concluded even after long time of installation in soil. Although established in a sulfide‐bearing environment, three of five electrodes at 150 cm showed a substantial increase (+500 mV) in EH during summer of the third and fourth years of investigation, which had low water tables. It is not clear whether the non‐response of two electrodes was due to electrode contamination or spatial variation in EH. When operating in reducing systems, this problem can be circumvented by installing a large number of electrodes or by a regular replacement of electrodes. Using properly constructed and permanently installed Pt electrodes, soil EH can be monitored for extended periods under wet and reducing soil conditions. 相似文献
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土壤硝态氮含量原位检测系统设计 总被引：2，自引：2，他引：0
针对现阶段土壤硝态氮测量成本较高、无法长期原位测量等问题,该研究提出了一种使用钛烧结滤芯收集土壤溶液,通过近红外光谱法检测土壤溶液中的硝酸根浓度进而得到土壤中硝态氮含量的方法,并设计了相应的检测装置。通过试验对比陶土头与钛烧结滤芯在不同土壤条件下的土壤溶液收集效果,选用钛烧结滤芯作为土壤溶液采集器收集土壤溶液,以近红外LED作为测量光源,采集人工配置土壤溶液的光谱数据,利用BP神经网络进行预训练建立硝态氮含量预测模型。建立的硝态氮含量预测模型其训练集皮尔逊相关系数、测试集皮尔逊相关系数、预测均方根误差分别达到0.997、0.995、3.43。实地测量土壤溶液并与硝酸根离子电极以及土壤养分速测仪进行对比,最大相对偏差为5.9%,可满足实际测量准确性要求。该套检测设备在深度为10～40 cm、含水率为15%以上的土壤中有较好的土壤溶液采集效果;检测装置的长期测量标准差为0.006,动态响应时间为1.4 s,具有良好的特性。试验结果表明,使用溶液吸光度数据建立的硝态氮预测模型具有较好的预测效果,可以应用于土壤溶液硝态氮原位监测,为长期自动测量土壤硝态氮及水肥一体化系统的搭建提供了一种可行的方案。 相似文献
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同化遥感监测数据提高土壤剖面湿度模拟精度,对区域农业发展等实践与理论领域具有重要意义。该文结合了集合卡尔曼滤波(ensemble Kalman filter,EnKF)方法与HYDRUS-1D模型,同化降尺度后的AMSR2(advanced microwave scanningradiometer2)微波土壤湿度数据,开展榆社、荫城2个实验站点的土壤剖面湿度模拟。结果表明:在2个实验站点,与直接使用HYDRUS-1D模型相比,同化具有一定误差的AMSR2土壤湿度数据对不同深度土壤湿度的模拟精度提高都发挥了作用,尤其是对于同化前模拟方案S1(4月1日站点实测含水量)与S4(4月1日遥感含水量),由于HYDRUS-1D模拟时输入了较少数量的土壤湿度数据,数据同化效果与土壤湿度模拟精度提高更为显著;同化前后不同深度的土壤湿度精度对比结果表明,同化效果随深度增加而逐渐减弱。 相似文献
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Compaction of an Eutric Cambisol under heavy wheel traffic in Switzerland — field data and modelling
Heavy agricultural machinery can cause structural degradation in agricultural subsoils. Severe structural degradation impedes plant growth. Therefore, compaction must be limited to layers that can be structurally reclaimed and remoulded with reasonable effort by tillage. The purpose of this study was to investigate the impact of a single pass with a sugar beet harvester on the soil properties of an unploughed Eutric Cambisol. Field measurements and laboratory testing were carried out in Frauenfeld, Switzerland. In addition 2D calculations of strain, stress and subsequent compaction were conducted using a three-phase (soil skeleton, pore water, and air) model for unsaturated soil incorporating a recently developed constitutive law. Model data were compared to the field measurements. Due to the pass of the machinery, the soil was compacted down to a depth of at least 0.15 m and at most 0.25 m. This compaction was indicated by an increase in soil bulk density and pre-consolidation pressure as well as by a decrease in total porosity and macroporosity. The surface displacement measured in the field was consistent with the calculated model data. The calculated and measured stresses at depths of 0.35 and 0.55 m stand in good accordance with each other, whereas at a depth of 0.15 m the pressure measured in the field exceeded the calculated pressure. In this study, we show the degree of compaction due to heavy wheel traffic and the suitability of a model approach to describe compaction processes. 相似文献
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Field traffic may reduce the amount of air-filled pores and cavities in the soil thus affecting a large range of physical soil properties and processes, such as infiltration, soil water flow and water retention. Furthermore, soil compaction may increase the mechanical strength of the soil and thereby impede root growth.
The objective of this research was to test the hypotheses that: (1) the degree of soil displacement during field traffic depends largely on the soil water content, and (2) the depth to which the soil is displaced during field traffic can be predicted on the basis of the soil precompression stress and calculated soil stresses. In 1999, field measurements were carried out on a Swedish swelling/shrinking clay loam of stresses and vertical soil displacement during traffic with wheel loads of 2, 3, 5 and 7 Mg at soil water contents of between 11 and 35% (w/w). This was combined with determinations of soil precompression stress at the time of the traffic and predictions of the soil compaction with the soil compaction model SOCOMO. Vertical soil displacement increased with increased axle load. In May, the soil precompression stress was approximately 100 kPa at 0.3, 0.5 and 0.7 m depth. In August and September, the soil precompression stress at 0.3, 0.5 and 0.7 m depth was 550–1245 kPa. However, when traffic with a wheel load of 7 Mg was applied, the soil displacements at 0.5 m depth were several times larger in August and September than in May, and even more at 0.7 m depth. An implication of the results is that the precompression stress does not always provide a good indication of the risk for subsoil compaction. A practical consequence is that subsoil compaction in some soils may occur even when the soil is very dry. The SOCOMO model predicted the soil displacement relatively well when the soil precompression stress was low. However, for all other wheeling treatments, the model failed to predict that any soil compaction would occur, even at high axle loads.
The measured soil stresses were generally higher than the stresses calculated with the SOCOMO model. Neither the application of a parabolic surface load distribution nor an increased concentration factor could account for this difference. This was probably because the stress distribution in a very dry and strongly structured soil is different from the stress distribution in more homogeneous soils. 相似文献
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黄土区小尺度坡面土壤含水率时空变异性研究 总被引：7，自引：2，他引：5
土壤含水率在水平和垂直方向上均具有高度的时空异质性,关于水平方向变异的研究取得了很大进展,而对垂直方向变异的研究较为缺乏。为掌握土壤含水率在剖面上的垂直变异特征,采用经典统计、地统计及分形分析相结合的方法,研究了黄土高原典型坡地剖面土壤含水率的时空变异性。结果表明:不同测定时间下的剖面土壤含水率均服从自然对数正态分布,在空间上均表现为中等变异性,沿土层深度方向的变化趋势均为增长型,且这种变化规律具有时间稳定性;剖面土壤含水率在整个研究区域尺度、微尺度上的半方差函数均可用指数模型进行很好地拟合,均表现出强烈的空间依赖性,并且这种规律几乎不随时间的变化而变化;不同测定时间下剖面土壤含水率在整个研究尺度上均表现出有限的自相似性,在小于2.00 m的间距尺度下具有稳定的自相似性,大于2.00 m间距尺度的自相似性比较微弱,分维数的大小与控制土壤含水率的主要过程有关;不同测定时间下剖面土壤含水率的空间自相关性基本一致,即当滞后距离小于3.20 m时为空间正自相关,大于3.20 m时为负自相关,等于3.20 m时为不相关,而在剖面土壤含水率之间的相关性达到了极显著水平。 相似文献
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On-the-go measurement of soil water content and mechanical resistance by a combined horizontal penetrometer 总被引：2，自引：0，他引：2
A combined horizontal penetrometer was designed for the on-the-go and simultaneous measurement of soil water content and mechanical resistance. The maximum sampling rate for both sensors was 10 Hz and the maximum operating depth was 20 cm. For the water-content sensor, its measurement principle depends on the electric field of the fringe-capacitance. In order to evaluate the applicability of this combined penetrometer, four experiments in the field were carried out. These experiments included: (1) soil water content profiles test; (2) soil compaction measurement test; (3) effect of the operating velocity on the water content and resistant force measurement; (4) effect of operating depth on the force measurement. The experimental results show that the combined horizontal penetrometer is a practical tool since it can provide more useful information of soil physical properties. 相似文献
20.
P. SCHJØNNING M. LAMANDÉ T. KELLER J. PEDERSEN M. STETTLER 《Soil Use and Management》2012,28(3):378-393
Subsoil compaction is persistent and can affect important soil functions including soil productivity. The aim of this study was to develop recommendations on how to avoid subsoil compaction for soils exposed to traffic by machinery at field capacity. We measured the vertical stress in the tyre–soil contact area for two traction tyres at ca. 30‐ and 60‐kN wheel loads on a loamy sand at field capacity. Data on resulting stress distributions were combined with those from the literature for five implement tyres tested at a range of inflation pressures and wheel loads. The vertical stress in the soil profile was then predicted using the Söhne model for all tests in the combined data set. The predicted stress at 20 cm depth correlated with the maximum stress in the contact area, tyre inflation pressure, tyre–soil contact area and mean ground pressure. At 100 cm depth, the predicted vertical stress was primarily determined by wheel load, but an effect of the other factors was also detected. Based on published recommendations for allowable stresses in the soil profile, we propose the ‘50‐50 rule’: At water contents around field capacity, traffic on agricultural soil should not exert vertical stresses in excess of 50 kPa at depths >50 cm. Our combined data provide the basis for the ‘8‐8 rule’: The depth of the 50‐kPa stress isobar increases by 8 cm for each additional tonne increase in wheel load and by 8 cm for each doubling of the tyre inflation pressure. We suggest that farmers use this simple rule for evaluating the sustainability of any planned traffic over moist soil. 相似文献